and Ergonomics Reviews of Human Factors

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Forensic Human Factors: People, Places, Products Ilene Zackowitz and Alison Vredenburgh Reviews of Human Factors and Ergonomics 2008 4: 75 DOI: 10.1518/155723408X342862 The online version of this article can be found at: http://rev.sagepub.com/content/4/1/75

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CHAPTER 3

Forensic Human Factors: People, Places, Products Ilene Zackowitz & Alison Vredenburgh Forensic human factors (HF) consultants apply the science of human factors to litigation. After someone has been injured and a lawsuit has been filed, attorneys will often seek the expertise of forensic HF consultants to analyze the incident and determine if features of the person, place, or product involved were causal factors in the incident. In this chapter we describe the conventions, guidelines, and procedures involved in a typical forensic HF case. In addition, we describe the human factors content areas that are most frequently addressed over the course of an HF evaluation.

INTRODUCTION Forensic human factors (HF) is the application of human factors/ergonomics theory and principles to help determine the contributing factors of system failures in the context of litigation. These failures often result in personal injuries and sometimes death. The HF expert analyzes the relevant aspects of the people, places, and products involved in the litigation at hand. This analysis may encompass issues including social, cognitive, organizational, physical, and environmental aspects of the case. Most forensic HF consultants’ cases are in civil litigation, although there are exceptions. For example, an HF consultant may be asked to opine regarding a criminal or victim’s reasonableness of conduct or to address handgun safety issues (see Hendrick, Paradis, & Hornick, 2008, for a thorough review of forensic HF gun safety issues). In this chapter we focus on the work of HF consultants in civil rather than criminal litigation. Historically, HF practitioners have been involved in the design of systems and products to reduce human error. Forensic HF practitioners differ from their nonforensic colleagues in that their primary goal is to determine how a system failure occurred (Noy & Karwowski, 2005). This orientation recognizes that human factors research and application may potentially assist in the dispute resolution process by providing insight into why an event may have occurred (Redding, Rogers, & Fisk, 2006). The underlying causes of events can be understood and explained better when qualified HF experts utilize the tools and techniques they have at their disposal. Human factors specialists traditionally worked in the early design stages of product and system development. However, as their expertise became more widely recognized, they began to analyze system failures that led to injury and/or costly production loses. Given this new direction and focus, it was necessary to develop methods for investigating and DOI 1518/155723408X342862. Copyright 2008 by Human Factors and Ergonomics Society. All rights reserved. Downloaded from rev.sagepub.com by guest on September 6, 2012

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analyzing the causes of human error in existing systems. This development did not go unnoticed by attorneys, and the field of forensic human factors was created (Sloan, 1999). The first mention of the applied field of forensic HF was in a special issue of the journal Human Factors entitled “Human Factors and the Law” (1972, Volume 14, Number 1).

Qualifications and Training Forensic HF is a professional endeavor that is not explicitly taught, even in the United States, where its practice is most prevalent (Noy & Karwowski, 2005). Professional practice in the forensics arena—in human factors or any other discipline—requires extensive knowledge, skill, and experience. Forensic practice also requires a particular type of individual who can effectively communication with nonexperts. A person with vast knowledge and experience in the area of human factors may make a terrible witness on the stand. He or she may speak over the heads of the lay jury members so that the testimony does not make an impact. Being an effective forensic HF practitioner requires the right blend of scientific expertise, personality, and communication skills. (See Babitsky, 2005, for a discussion of personality, communication, and other factors that make an expert stand out as exceptional.) Human factors litigation issues include personal injury and property damage accidents that typically involve motor vehicles, consumer products, industrial machines and processes, and slips, trips, missteps, and falls. In order to effectively and thoroughly evaluate such cases, litigation consultants must have sufficient education and relevant experience. They must be well versed in the content areas and issues that will be relevant for any particular case. Generally speaking, for HF cases, these areas often include foreseeable use and misuse, human error, human perception, biomechanics, anthropometry, decision making, reaction times, fatigue, training, safety, and organizational psychology (Askren & Howard, 2005). Experts are qualified by their knowledge, skill, experience, training, or education (Federal Rule 702). The legal rules that define the requirements for expert witnesses do not explicitly require graduate degrees or specific types of experience. Despite the lack of specific educational requirements, HF experts usually have an advanced degree in psychology, human factors, engineering, or communication (Vredenburgh & Zackowitz, 2005). To use the science effectively in litigation, the forensic HF practitioner must have solid qualifications, as evidenced through appropriate education, experience, and training.

LITIGATION CONSIDERATIONS The field of human factors has applications in a wide variety of industrial, health care, service, and manufacturing industries. Because the scope of HF work is so varied, so too is the experience of practicing professionals. It is important that attorneys retain an HF expert with the appropriate background for a given case. The variety of chapters that make up Reviews of Human Factors and Ergonomics is a testament to the diversity of topics in which HF professionals may specialize. For example, some focus on medical issues, others specialize in visibility and driver reaction time Downloaded from rev.sagepub.com by guest on September 6, 2012

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issues, and yet others focus on the office environment. Legal standards and court decisions determine what scientific evidence is admissible, or usable, for a given case.

Legal Standards There are legal standards that must be considered when practicing forensic HF. By definition, expert testimony deals with areas outside the knowledge domain of the judge or jury (Papinchock & Landy, 2005). This may result in an inclination to accept expert testimony as “truth.” Legal standards for expert testimony aim to ensure that the fact-finder (judge and/or jury) hears only expert testimony that is supported by a solid scientific foundation. The relevant legal standards for expert testimony are Frye and Daubert. Frye. The Frye test, also known as general acceptance, has become the criterion that determines whether certain scientific evidence is admissible in court. The Frye case (Frye v. United States, 1923) considered the use of the modern polygraph (lie detector) machine and whether it showed scientifically that a person is not being deceptive (Hess, 2005). In that case the court held that the court will go a long way in admitting expert testimony deduced from a wellrecognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs. (Blau, 1998, p. 422)

In other words, the scientific basis used in making expert opinions must have general acceptance in that particular field of study. Many jurisdictions still use the Frye test to determine whether expert testimony is admissible as legal evidence (Hess, 2005). However, it has been criticized because of the de facto waiting period required before the general acceptance of new theories and their impact on emerging science (Papinchock & Landy, 2005). Daubert. The U.S. Supreme Court provided a ruling in Daubert v. Merrell Dow Pharmaceuticals (1993) that had a direct impact on the guidelines for admissibility of expert testimony in federal court. In that ruling, the Supreme Court established that the Frye test had been superseded by the Federal Rules of Evidence (FRE) enacted in 1975 (Papinchock & Landy, 2005). In its ruling, the Court set forth tests for determining, under Rule 702 of the FRE, whether scientific testimony could be allowed into evidence. The Court required that proposed testimony be logically related to the facts of the case and that it be grounded in the methods of science (Redding et al., 2006). The requirements for admissibility under Daubert are as follows: 1. 2. 3. 4.

The proposed testimony will assist the fact-finder in resolving factual issues. The theory has been subjected to peer review or publication. The potential rate of error and methodological standards are identified. The technique is generally accepted in the relevant scientific community.

These considerations are neither exclusive nor inflexible; courts are free to apply them to meet the factual pattern of a particular case (Redding et al., 2006). Downloaded from rev.sagepub.com by guest on September 6, 2012

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FRE 702 was amended in 2000 to reflect a distillation of the post-Daubert requirements (Redding et al., 2006). It now reads as follows: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise if 1) the testimony is based on sufficient facts or data, 2) the testimony is the product of reliable principles and methods, and 3) the witness has applied the principles and methods reliably to the facts of the case.

The applicability of the Daubert decision to HF experts was clarified in Kumho Tire Company v. Carmichael (1999), in which the U.S. Supreme Court ruled that the Federal Rules of Evidence govern all expert testimony, even social sciences such as human factors, in which the scientific method is not always applicable. It found that an expert’s testimony concerning a tire failure case was subject to Daubert; thus, the Court decided that FRE 702 does not differentiate between scientific and nonscientific knowledge (Papinchock & Landy, 2005). In theory, the Daubert decision has reduced the amount of so-called junk science in a courtroom. In cases in which HF experts are used, substantial emphasis is placed on the judge’s role as interpreter and gatekeeper, often in determining on a case-by-case basis if the expert utilized appropriate scientific methods in forming his or her opinions (Papinchock & Landy, 2005).

Preparing for a Human Factors Case In order to perform an effective forensic HF analysis, first the legal standards just discussed must be considered. The HF practitioner must have sufficient education and experience to qualify under current legal requirements. The “client” in a forensic consultation is usually the attorney who retains the consultant. The plaintiff or defendant in the lawsuit is the attorney’s client, and the attorney is a client to the expert. To clarify, just as an attorney will bill the client (plaintiff or defendant) for the time he or she works on the case, the expert will typically invoice the attorney for the work he/she does. An open and forthright relationship between the expert and attorney will ensure that all relevant information is shared and that no surprises arise as the trial date approaches. There are several ways in which litigation consultants may be contacted by attorneys. They may be located through membership in professional societies and forensic organizations. These organizations typically publish a member consultant’s directory, which is distributed widely to law firms and lawyers. Once established, contacts are typically made through referrals by attorneys or other experts. Some large consulting companies hire individuals with the right educational background or work experience. In addition, many HF practitioners choose to open their own consulting practices, which may or may not include forensic projects. Available data indicate that about 27% of HF professionals practice in industry and about 10% work in private practice (Helander, 2005). Only a small fraction of those professionals work in the forensics arena. There are several steps to follow once the HF expert is approached with a possible forensics case, described next. Downloaded from rev.sagepub.com by guest on September 6, 2012


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Preliminary assessment of facts of a case. Upon first contact with an attorney, an expert will be provided with information regarding the general nature of the case and its probable schedule. At this time, the expert will likely establish a financial relationship with the attorney (Askren & Howard, 2005). Before performing any work, it is necessary to determine that no conflicts exist, such as knowing a party involved in the lawsuit. Once satisfied that no conflicts exist, the attorney retains the expert’s services, and the formal case analysis begins. The HF expert’s first task is to determine if he or she has the correct expertise to address the issues of interest to the attorney. Attorneys frequently have photos of the product or environment involved in the incident, or they may simply describe how the incident occurred. Experts evaluate this preliminary information in order to determine whether they have the qualifications to work on the case. Reviewing discovery materials. The typical next step in conducting the HF analysis is to review discovery materials supplied by the attorney. The purpose of discovery review is to gain as complete an understanding of the nature of the incident as possible. This understanding will involve learning about any environmental, equipment, human, process, and organizational conditions that may be relevant (Askren & Howard, 2005). Discovery materials typically include, but are not limited to, the following: deposition transcripts, recorded statements, incident reports (from police, an insurance company, or a business), legal documents (e.g., complaint, interrogatories, requests for production), product information, medical documents, and photos. The discovery materials should represent all the information available on the case. However, sometimes attorneys limit what they provide to what they think may be relevant to an HF evaluation. In some lawsuits, there is so much discovery information that it is neither practical nor desirable to attempt to review it all. Typically, the attorney is not an HF expert and might not know what is and is not important for a thorough HF analysis. In addition to the discovery materials provided by the attorney, the analysis should include relevant data, research, and publications in the field that will assist in the investigation. For example, weather data and sunrise and sunset information from the day of the incident are often useful. Site or product inspection. An inspection of the site or product involved in the incident is often the next step of the evaluation. Although it is not always necessary to perform an inspection, it is usually a good idea. Even if the environment has been changed and no longer exists as it did at the time of the incident, the attorney may still request an inspection by the HF expert. The expert who has chosen not to perform such an evaluation will almost certainly be asked by the opposing attorney to defend this decision when a deposition is taken. The goal of an inspection is to help the HF expert determine and/or understand how and why the incident occurred. The exact steps taken during the inspection depend on the specific facts of the case. Observations, photographs, and measurements are typically taken. Other specialized tests may also be made during inspection. For example, it might be important to evaluate the visibility of liquids on a walking surface. Coefficient of friction (COF) testing is often, but not always, performed for slip-andfall cases. (We discuss COF testing further in a later section.) Force testing, light meter Downloaded from rev.sagepub.com by guest on September 6, 2012

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testing, and line-of-sight evaluations are also common for premises injury cases. The expert should ensure that he or she is qualified to perform the required testing; the expertise of the person conducting any testing procedure is likely to be questioned by the opposing attorney. Regardless of which party in the lawsuit has retained the expert, it is often useful for a person who was actually involved in the incident to be at the site inspection. This gives the expert the opportunity to interview the person regarding his or her first-hand recollection of the event. Task analysis. Sometimes it is worthwhile to perform a task analysis when investigating a case involving a product or work environment. Such an analysis identifies and describes what the user of the product or system needed to do in order to accomplish the task he/she was performing at the time of the incident. A forensic task analysis helps in answering specific questions relevant to the case at hand, including these: a. b. c. d. e.

What were the intentions of all parties involved (i.e., what were they trying to do)? What was each party’s behavior (i.e., what did they actually do)? Was information available that may have prevented the incident? Did personal characteristics of any involved party contribute to the incident (Kurke, 2005)? Did the equipment or environmental design contribute to the incident?

Answering these questions during a product or site inspection may help the judge and/or jury determine if the product or user environment was unreasonably dangerous, if the incident was foreseeable, and if anyone’s conduct was unreasonable (Kurke, 2005). Reports. After all available data for the case have been reviewed, the client attorney may request a formal report of the findings. For federal court cases and in many state courts, an expert report is required. It is important to determine if your client needs a report and the required format of the report, which is usually based on jurisdiction. Even in situations in which reports are not required by statute, an attorney may request a written report. Sometimes an attorney may feel reports are not necessary because the expert findings and opinions will be established during the deposition process. Deposition. The purpose of deposition is to afford the opposing counsel the opportunity to directly examine the expert to determine the expert’s qualifications, fully understand the analyses and investigations the expert has performed, and explicitly enumerate the findings and opinions and bases for those opinions (Askren & Howard, 2005). Usually the plaintiff’s expert witness is deposed first by the defense counsel, followed by the defense expert witness, who is deposed by plaintiff’s counsel. The defense expert often has the opportunity to review the opposing expert’s deposition prior to his/her own, and he/she may choose to offer rebuttal opinions. Typically the opposing attorney will request and pay for the expert deposition. After the deposition is concluded, the court reporter prepares a transcript of the deposition testimony. The expert will be given an opportunity to review the transcript and correct any errors that may exist. Downloaded from rev.sagepub.com by guest on September 6, 2012


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Trials. The vast majority of civil cases (80%–90%) are settled without going to trial. If a case continues to trial, the opposing counsel may challenge an expert’s credentials and expertise in an attempt to establish that the witness is not a content area expert. Assuming the expert is qualified by the judge, the credentials of the HF expert are first presented through direct examination by the client attorney (Askren & Howard, 2005). Then the client attorney will ask the expert to offer his or her opinions about the case. After direct examination, opposing counsel begins cross-examination of the subject matter covered during direct examination. Then re-direct and re-cross examination follow until both sides feel that all areas have been covered and the expert is dismissed by the court. As part of the HF expert’s testimony, supporting evidence in the form of human factors guidelines, peer-reviewed research articles, technical reports, and handbook chapters may be introduced. It is important to note that these various sources of information are not viewed as equally convincing to a jury. There are a variety of authorities on which opinions are based, some providing stronger support than others, but all are acceptable depending on the case. Cohen and LaRue (1997, 2006) proposed a hierarchy of sources based on the ease with which the sources can be supported. These bases, in descending order of strength, are as follows: a code or legal requirement, a voluntary standard, industry custom and practice, a professional handbook, scientific literature, an empirical study, and professional judgment. At times, the testimony of HF experts is challenged by the opposing attorney. Reasons an attorney may oppose the introduction of human factors/ergonomics testimony include the following: 1. The attorney has not retained an HF expert and realizes the opposing expert’s testimony may be harmful to his or her positions. 2. The attorney feels the HF testimony can be determined based on the jurors’ own common experience. 3. The attorney cites Daubert and challenges the field for its scientific credibility (HFES Forensics Professional Group, 2004).

A number of arguments can be made to deflect Daubert challenges, including the following: 1. 2. 3. 4. 5.

Human factors is an established and internationally recognized scientific discipline. There is scientific foundation for the peer-reviewed HF research. Many academic programs offer undergraduate and advanced degrees in the discipline. The government and many Fortune 500 companies employ HF professionals. HF research is published in many peer-reviewed scientific journals.

For a thorough discussion of the arguments supporting HF expert testimony, see the Position Paper Supporting Human Factors and Ergonomics Practitioners in Forensics (HFES Forensics Professional Group, 2004).

PEOPLE Every forensic HF case has one common element: people. People designed the environment or product at issue in the case, a person used the product or interacted with the Downloaded from rev.sagepub.com by guest on September 6, 2012

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environment, and a person suffered bodily injury or property damage as a result of some event or incident. When such incidents occur in an organizational setting, other people may be involved in training and supervision. In this section we examine those topics that should be considered by forensic HF consultants when addressing the human aspect of their evaluation.

Reasonableness of Conduct When conducting a human factors analysis, it is important to analyze the characteristics of the individuals involved in the case. Attorneys often engage HF experts with an understanding of psychology and ask them to address whether the behavior of plaintiffs and/or defendants was “reasonable.” Reasonableness, in legal settings, refers to behaviors consistent with societal norms for a given population (Zackowitz & Vredenburgh, 2005). Many individual differences should be considered when determining reasonableness of human actions, several of which will be discussed in this section. The concept of reasonableness can apply to either party in a litigation matter. Human factors experts frequently evaluate the reasonableness of both manufacturer/ designer/employer and user behavior. For example, if a manufacturer designed a product with known (or knowable) hazards and fails to warn of those hazards, it may be held responsible for injuries that result. This is because the behavior of the manufacturer might not be reasonable based on its legal duty to warn (Pease v. Sinclair Refining, 1939; Vredenburgh & Zackowitz, 2005). Maintenance of public properties is another area in which reasonableness of conduct should be considered. The HF expert may evaluate the plaintiff ’s conduct to determine whether his or her behavior while using a product was appropriate or not, or if the behavior was foreseeable. Perhaps the person’s behavior constituted a foreseeable misuse of the product, which the manufacturer should have considered. For example, a young child injured on a playground may have been behaving consistently with others at her stage of development, but her level of supervision was insufficient. The person supervising the child may have acted unreasonably. Because of the differences in the physical and cognitive abilities and limitations of various populations, people may be held to different standards of conduct. What is reasonable and foreseeable for one population might not be so reasonable or foreseeable for another. These issues should be considered for all parties involved in the litigation.

Effects of Aging As the number of older adults in the United States increases, more attorneys are retaining HF experts to address how age-specific factors may be related to reasonableness and foreseeability of behavior. Just as cognitive and physical changes occur with age (e.g., Rogers, Stronge, & Fisk, 2006), the types of legal cases for which HF experts are retained also vary as a function of age. For example, for adults age 65 and above, pedestrian fall accidents and motor vehicle accidents are more frequent than for younger adults because of decrements in physical and cognitive processing capabilities. Typical accidents involving preschoolers occur on the playground and in traffic. Accidents seen in adolescent Downloaded from rev.sagepub.com by guest on September 6, 2012


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populations often involve risk-taking behavior and lack of supervision. Interestingly, crashes and the associated injuries and deaths disproportionately affect both younger and older drivers (Lee, 2006). Vision. Visual acuity begins to decline after the age of 40 (Schneider & Pichora-Fuller, 2000). The most commonly recognized age-related form of vision decline is correctable. However, even with such correction, visual acuity, contrast sensitivity, dark adaptation, and contrast discrimination begin to decline after 45 years of age. Older adults may need two to three times more contrast than younger observers to be able to see small or mediumsized targets (Davis & Loftus, 2005). As a result of these types of deficiencies, older people may have difficulty in darkened movie theaters, where contrast is limited. Pathologies of the eye also increase with age, including cataracts, glaucoma, and macular degeneration (Michaels, 1993). Not only does visual perception tend to become less precise or accurate, especially under conditions of poor lighting or poor contrast, but it becomes slower with age as well (Jacoby, Marsh, & Dolan, 2001). Thus, for older individuals, safety-critical cues need to be available for longer periods. Such deficiencies can lead to accidents—for example, when a pedestrian fails to notice a barrier in a walkway or an elevation change. Night driving introduces substantial vision-related difficulties for aging drivers. Older people have greater difficulty with night vision and need more time to recover from glare (Klavora & Heslegrave, 2002). Because visual acuity declines substantially with age, especially in conditions of low illumination, older drivers’ vision tends to be worst when it is needed most. In traffic accidents involving the elderly, impairment in one or more visual skills may well play a causal role (Davis & Loftus, 2005). Despite the fact that older drivers tend to be aware of their visual deficits and often respond by driving slower, shorter distances, and less often during rush-hour and nighttime, they are still at a greater risk of accidents compared with 16- to 25-year-old drivers (Klavora & Heslegrave, 2002). A decline in peripheral vision with age results in a reduced likelihood of detecting objects in the peripheral field, less accurate discrimination between objects in the periphery, and less accurate motion detection (Davis & Loftus, 2005). One study (Johnson, 1986) found that adults older than age 70 have a visual field of 140 deg, whereas younger adults typically have peripheral vision in the 180-deg range. Distracters, such as irrelevant or similar objects in the periphery, tend to reduce the useful visual field (Sekuler, Bennett, & Mamelak, 2000). The potential consequences are obvious of failing to detect important stimuli in the periphery, such as traffic signs, pedestrians, and oncoming traffic. Memory. Modern memory theory suggests that human memory operates in three phases (Davis, Kemmelmeier, & Follette, 2005): (a) acquisition or encoding, when information is first transferred into memory; (b) storage, when information is maintained in memory over some period; and (c) retrieval, when information is located and retrieved from storage. Working memory is the sum of the processing resources available at any given moment to perform cognitive operations (Baddeley, 1986). Age-related declines in working memory are well documented and appear most strongly in tasks demanding stronger cognitive processing capabilities. For example, information manipulation (problem solving), multitasking, and tasks that require attention to multiple items of information are particularly age sensitive (Davis & Loftus, 2005). Downloaded from rev.sagepub.com by guest on September 6, 2012

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Memory is dependent on successful information encoding, which is in turn dependent on adequate attention. Partly as a result of age-related declines in attention control, older adults are more susceptible to both errors of omission (not remembering things that did happen) and errors of commission (remembering things that did not happen; Craik, 2000). These decreases in memory for older persons have important implications for individuals who investigate incidents in a forensic setting. Specifically, if an older adult is involved in an incident, it is important to interview that person as soon as possible after the event in order to gain the most accurate information. Typically, the litigation process does not commence immediately after an incident occurs; therefore, time is of the essence when gathering information from witnesses and parties. Often, involved parties provide a witness statement shortly after an incident occurs and provide deposition testimony sometimes many months or even years later. The HF expert must evaluate differences in the witness accounts and determine which version of events is most likely correct. Physical abilities. As people age, the body experiences physical changes that must be considered when an HF expert performs an accident investigation. Older Americans are disproportionately represented among accident victims (Davis & Loftus, 2005). Pedestrians over the age of 70 are more likely to be involved in a severe accident than are younger walkers (Dewar, 2005). According to a 1993 study, people over age 64 accounted for over 22% of pedestrian fatalities but only 12% of the total population (Choueiri, Lamm, Choueiri, & Choueiri, 1993). Fall-related accidents are particularly likely to be influenced by aging factors such as muscular weakness, arthritis, abnormal gait, medication side-effects (Zackowitz & Vredenburgh, 2002), physical fragility, brittle bones, and longer recovery times (Dewar, 2005). In order to walk safely, a person must coordinate multiple systems simultaneously, including perception, cognition, and motor resources. Increases in accidents among the elderly occur partly because of degradations in these necessary physical functions. Older people walk with a shorter stride and have a greater tendency to drag their toes during the swing phase of the stride. Therefore, they have less ability to clear obstructions or changes in elevation in their path, resulting in a loss of balance and subsequent fall. It is not unusual for older adults to trip on elevation changes smaller than a half inch. These types of hazards are typical on sidewalks and transitions in flooring surfaces. In addition, older people have more difficulty recovering after they lose their balance, resulting in more incidents and more significant injuries for this population (Zackowitz & Vredenburgh, 2005). Because of gender-associated limitations in the older population, senior women outnumber men in incidents of fall-related injuries. For example, women over the age of 75 typically exhibit some degree of bow-leggedness and have a narrower walking and standing base than do men in the same age group. This results in a less stable stature. Further, when older women suffer a fall, osteoporosis leads to more severe injuries (Zackowitz & Vredenburgh, 2002). The use of assistive devices such as canes and walkers can increase the older pedestrian’s stability and assist in recovery after a loss of balance. Downloaded from rev.sagepub.com by guest on September 6, 2012


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Response times. Perception-reaction time, the time it takes for an individual to respond to a given stimulus, is critically important in many accident scenarios, particularly driving situations. The components of perception-reaction time are search, detection, recognition, decision, and action (Dewar, 2005). For example, a person trying to follow directions often needs to make quick choices and execute them in complex and rapidly changing contexts (e.g., in a shopping center parking lot). Impairments of processing and response speed can seriously compromise the safety of older adults, who tend to perform best under simple conditions and without time pressure (Davis & Loftus, 2005). The difficulties older adults experience in perception, choosing responses, and preparing and executing their responses may result in slower reaction times, which can contribute to accidents. Studies have shown that older drivers display a significant increase in reaction time. Older drivers are slower by 15% to 25% than younger drivers in responding to stimuli (Olson & Farber, 2003). In studies using driving situations involving roadway hazards, brake reaction time was shown to be longer for people age 50 to 84 than for people age 18 to 40 (Olson & Sivak, 1986). Furthermore, for every 5-year increase in age between the ages of 15 and 75, brake reaction time increases by approximately 2% (Stelmach & Nahom, 1992). Slower reaction times mean that there is less time to initiate evasive maneuvers to avoid an accident when one is imminent. During accident reconstructions, HF experts must often determine how much time a person had to respond to a critical stimulus. All facets of the incident can be re-created and then a range can be determined for the perception reaction times based on most- and least-favorable conditions. Some evidence suggests that decreased cognitive processing speeds account for agerelated declines in cognitive task performance (Salthouse, 1996). Keeping in mind that older people process information accurately but slower than their younger counterparts may be an important factor in certain investigations. For example, if a jaywalker crossing the street is injured by an elderly driver, it may be that the walker’s behavior was unreasonable, not the driver’s, given the latter’s slower processing and reaction times.

Children It is important to keep in mind that children have abilities and limitations that are based on their developmental level. Therefore, in order to gain a realistic understanding of behavioral expectations, it is important to consider those age-related capabilities and limitations that may be relevant to the forensic analysis. Because of their inherently limited cognitive and physical abilities as well as their inexperience, children are held to different standards of conduct than are older individuals (Beran, Nielsen, Altkorn, Milkovich, & Rider, 2007). For example, a toddler who runs into the street and is struck by a car is behaving within his anticipated level of functioning. A teenager who does the same thing would be held to a higher standard of conduct. Developmental issues. The behavior of children is different from that of adults. The behavior of preschoolers differs from that of adolescents. Each child is unique, yet children also exhibit consistent similarities as they develop (Brown & Beran, 2008). Children’s conceptions of safety are poorly formulated and their mental representations of relevant Downloaded from rev.sagepub.com by guest on September 6, 2012

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behaviors are not well developed (Dewar, 2005). Children’s understanding and knowledge are limited by age, development, and experience in the world. It is often difficult for children to understand the rationale behind certain rules that were created by adults. Children of different ages are at risk for involvement in different types of accidents based on their cognitive and physical developmental level, which is not necessarily the same as their age level (Zackowitz & Vredenburgh, 2005). For children in all age groups, and for all causes of injury, boys are at greater risk of unintentional injury and death than are girls. This is primarily because of boys’ greater exposure to hazardous activities and patterns of risk taking and rough play (Kogan, 1995). Preschoolers (age 3 to 6 years) may need adult help for certain physical tasks, but they may not necessarily ask for help. At this age, their physical abilities develop quickly: A child who was struggling to climb a ladder at the playground one week may have mastered that skill by the next week. Young children need simple and explicit directions to perform most activities and often require continuous prompts to keep them on task. They also need close supervision to keep them safe. Allowing a child to play with a toy intended for older children without supervision, or to play near hazards such as bodies of water, frequently leads to injury in play-related accidents. One feature common in preschoolers is the ease with which they can be distracted. They tend to pick up a sight or sound of interest and focus on it while ignoring other things going on around them (Zackowitz & Vredenburgh, 1998). This characteristic may lead to several common types of accidents, including traffic accidents and playground collisions. Even when children have the physical capabilities to perform a wide array of behaviors, they can get themselves into precarious situations because they lack the cognitive skills to handle difficulties that may arise. Efficient problem solving requires many skills not usually developed among preschoolers, including the ability to notice, evaluate, and correct one’s errors. These skills require considerable brain maturation, which usually does not occur during the preschool years. Children are typically between the ages of 6 and 8 before they perceive hazards such as a traffic accident or a fall from an elevation as a threat. Adolescents (from 12 to 14 years of age) often strive to develop their own unique personalities. They typically choose not to behave within the confines of their parents’ expectations and the greater demands of society. Children in this age group have the cognitive ability to think through the consequences of their behavior but usually do not consider all the possible outcomes (Brown & Beran, 2008). They often act impulsively, and peer pressure may drive adolescents’ behavior more than their own independent thought processes (Hoffman, Paris, & Hall, 1994). For example, adolescents may be dared to climb atop a building and jump off. The social pressures that exist at this age must be considered in a forensic investigation. Because adolescents are at an age when the events occurring in their lives seem allimportant, they often disregard other important information to the detriment of their own safety (Zackowitz & Vredenburgh, 2005). They may be so focused on a single aspect of a situation, such as impressing their peers, that they fail to notice or choose to ignore information concerning threats to their safety. Adolescents also tend to think in terms of a personal fable (Elkind, 1985)—that is, a young person’s belief that he or she is generally indestructible. Teenagers who engage in dangerous activities such as drinking and driving, drug use, and unsafe sex are Downloaded from rev.sagepub.com by guest on September 6, 2012


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demonstrating their belief in the personal fable of indestructibility. They also believe that they will not face negative consequences. When adolescents engage in risky conduct that results in litigation, these factors should be taken into consideration. Schools. Today, many children live in single-parent households or in situations in which both parents work at full-time jobs. In such cases, it is not always possible to monitor a child’s safety without relying on outside assistance from sources such as day care centers, preschools, and kindergartens. Although most schools have barrier systems to protect children (i.e., locked-down school campuses), these are not foolproof. Teachers of preschoolers and kindergarteners usually know how their students get home; if they see a youngster wandering around campus alone, the child will be escorted to the office so that a parent can be called. Preschool accountability should be carried out on a one-on-one basis, with each student released to a responsible adult. HF experts are often called to review a school’s barrier protection and release policies to determine if they may have contributed to a child’s being injured after release from school. School-related cases are common in the field of forensic human factors. For example, a child might be injured when walking home from school, though he or she was not authorized by a parent to do so. As a case in point, one child was killed when trying to cross the street to catch a bus that arrived earlier than usual; the child was trying to avoid harassment by older children on the later bus. In such cases, HF evaluation of the school’s policies, procedures, and supervision is often relevant. Playgrounds. Playgrounds enable children to develop physical and social skills in a fun and stimulating environment. As children develop the skills needed to play successfully on playgrounds, accidents and injuries are possible. User-environment fit is important on playgrounds to balance safety with the child’s need for creativity, challenge, and novelty (Vredenburgh & Zackowitz, 2008) and to enable children to refine their cognitive and motor skills (Frost, 1999). Improper playground design and inadequate supervision can contribute to injuries. Injuries tend to occur when task demands exceed children’s ability to safely complete them (Wallis, Cody, & Mickalide, 2003). Young children may misuse playground equipment (i.e., walk up the chute portion of the slide) or use equipment that is not age-appropriate. Older children may look for more exciting ways to use equipment, such as climbing over the tops of large structures that are meant to be accessed interiorly. In the areas not intended for access, play structures do not have safety features, such as handholds and railings, so accidents may result from this unintended use. It is typical for playgrounds to have a play area for children age 3–5 with lower platforms and slides and another area with more challenging structures for children age 6–12. Signage indicating the age-appropriateness of equipment is often provided and is intended to change the behavior of supervising adults. Adequate supervision is important because a responsible adult will help guide young children toward safe ways to play (Vredenburgh & Zackowitz, 2008). Playground maintenance issues are often relevant in forensic investigations. If a playground is in ill-repair, with sharp protruding or rusted parts, a child may be injured. Downloaded from rev.sagepub.com by guest on September 6, 2012

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Because many injuries occur as a result of falling, the playground floor surface must be capable of absorbing the forces from falls. Schools and municipalities are responsible for inspecting and maintaining their playground areas in a safe condition. Children and traffic. For young children under the age of 6, traffic is a significant danger. Among other dangerous beliefs, young children reason that if they see a car, the car must be able to see them. Typically, children fail to perceive traffic as a threat or hazard until they reach the age of 6 to 8 years. Before that age, they may not have matured cognitively enough to understand adult traffic rules (Zackowitz & Vredenburgh, 1998). As noted in the discussion of playgrounds, young children are egocentric and may be overly focused on the task at hand. They do not think about consequences and dangers. Therefore, if a ball is thrown into the street, a young child’s primary concern is to retrieve it, and he does not consider the possibility of dangerous passing traffic. To exacerbate this tendency, children’s field of vision is one-third narrower than that of adults; therefore, they are less likely to see critical peripheral stimuli (U.S. Department of the Interior, 1995). Children are also at increased risk as occupants of vehicles. Wallis et al. (2003) reported that motor vehicle occupant injury is the leading cause of injury-related death among children. In 2000, more than 1,600 children age 14 or younger died in vehicle crashes (Centers for Disease Control and Prevention, 2003). Children who ride unsecured, sit in the wrong size or type of car seat, or sit in a car seat that has been installed improperly are at increased risk of being injured in a motor vehicle accident (Cody, Mickalide, Paul, & Colella, 2002). These issues may be evaluated by considering the reasonableness of conduct of the driver and his or her child-protective behaviors.

Expectations and Safety Compliance Expectations—including a person’s attitudes, beliefs, and hazard perception—influence how an individual will approach and interact with virtually any hazardous situation (Vredenburgh & Zackowitz, 2006). A person’s knowledge base, whether accurate or not, will influence related behaviors. For example, research consistently demonstrates that the more familiar people are with a product, the lower do they perceived its hazardousness (Wogalter, Breslford, Desaulniers, & Laughery, 1991). This is because most interactions do not result in injuries—so-called benign experience. For example, a person who has used a power saw with multiple benign experiences will have the expectation that the tool does not pose a threat of injury. The user’s familiarity leads to a decreased perception of the relevant risk associated with the tool, an expectancy that may in turn reduce the user’s safety compliance. Conversely, the more hazardous a product or activity is expected to be, the greater the likelihood of self-protective behavior on the part of the user (Vredenburgh & Zackowitz, 2006). If a person knows or has heard about someone who was injured by a certain product, she is more likely to comply with safety-related information because she knows there is a true risk of injury.

PLACES: ENVIRONMENTAL DESIGN Human characteristics and behavior interact with features of the environment to produce an outcome. Most of the time, these outcomes are benign or even beneficial. Sometimes, Downloaded from rev.sagepub.com by guest on September 6, 2012


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however, this interaction causes injuries (or worse). When conducting a forensic HF evaluation, one should always include careful consideration of the usage environment in the analysis. A wide range of environmental components, natural as well as manufactured, often must be addressed in order to determine which characteristics have the most significant effects on the incident being analyzed (Bakken, 2005). Various codes or standards recommend or require that the built environment be designed and maintained so it provides an acceptable level of safety and accessibility for all people (Johnson, 2005). In this section, we examine how the design of public, private, and work environments is related to forensic HF analyses, and we review relevant measurement and code issues.

Public Places Public places include all those locations that are open and available to members of the community, such as stores, sidewalks, parks, and malls. Because these places are accessed by a broad range of individuals, their design must be consistent with the expected abilities of, for example, both young and old individuals and those with and without physical disabilities. Given the wide variety of existing environments, with their unique characteristics and design features, it is not surprising that some person-environment interactions turn out badly. The question the forensic HF investigator must ask is which, if any, features of the environment contributed to the causation of the incident under analysis. Pedestrians generally expect walking surfaces in public places to be uniform and clear of hazards and obstructions. If a hazard does exist along a walkway, the pedestrian must perceive and recognize it in order to reduce the likelihood of a fall. Slips, trips, and falls are more likely to occur when environmental design and conditions violate a pedestrian’s normal expectations or when sufficient sensory cues are not available (Cohen & LaRue, 2005). Causes of slips and falls are complex, and prevention approaches are often reactive, driven by injury trends and high-cost lawsuits. Causal factors often include a general disregard for industry standards and guidelines, inappropriate floor design, poor housekeeping, or insufficient management involvement (Gielo-Perczak, Maynard, & DiDomenico, 2006). In the next section, we focus on characteristics of floor surfaces that can result in falls, which are the most common accident injury pattern. Unintentional falls are nearly always preceded by a misstep, an unintentional departure from a walking gait appropriate for the walkway surface. A misstep can be attributed to a number of factors, including individual physiological conditions, inattention, poor design, inadequate lighting, or perceptual inadequacy (i.e., camouflaged design feature; see Johnson, 2005). Missteps and falls typically occur because of an unexpected change in level or traction or because of unexpected stair geometry. The task of controlling movement is complex and requires a multidisciplinary approach to determine why the fall occurred (Gielo-Perczak et al., 2006). Trip hazards. When a pedestrian unexpectedly encounters an impediment in the walking surface, a trip may occur. The most common scenario for a trip is when a person’s foot in the swing phase is stopped short in its forward movement. If this happens, the Downloaded from rev.sagepub.com by guest on September 6, 2012

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momentum of the body will carry its center of gravity forward and a stumble or fall may result (Bakken, 2002). Trips usually occur over impediments that are unmarked and provide few visual cues to alert the pedestrian to their presence. If the impediments were marked or expected, the pedestrian would perceive their existence and take appropriate actions to avoid or safely traverse them. Examples of situations leading to trip incidents include, but are not limited to, unmarked or unpainted tire stops, speed bumps, potholes, sidewalk uplifts, and items placed in unexpected areas (Cohen & LaRue, 2005). Changes in walking surface height need not be large to lead to possible trip-and-fall scenarios. Trip hazards ranging in height from 3/8 inch to 1/2 inch appear to be the tripping threshold for most pedestrians, as they are subtle enough not to be perceived by a pedestrian scanning the walking surface yet significant enough to catch a toe or shoe heel. Older people are particularly susceptible to trip-and-fall accidents because of age-related reductions in the minimal clearance that the swinging foot achieves when taking a step. For this population, there is often less than half an inch between the foot and floor during the swing phase (Cohen & LaRue, 2005). Many voluntary standards are in concurrence that changes in elevation greater than 1/2 inch should be transitioned by a ramp (i.e., ASTM, Title 24, ADA, and ANSI). The best approach to reducing the occurrence of trip incidents is to eliminate elevation changes in the walking surface. An example is to grind even the edges of lifted sidewalk sections. When it is not possible to simply eliminate the edge (as with a necessary single step), it should be marked to make it easily visible. Floor friction. Slips are caused by a reduction of traction between the bottom of footwear and the walking surface (English, 2003). Simply put, when a pedestrian’s foot loses traction while walking, he or she has slipped. Slip-and-fall incidents can occur on flat or sloped surfaces, as well as on stairs. Slips generally occur at the points of greatest instability in the gait cycle, the point of heel contact (Gielo-Perczak et al., 2006). At these times, the weight of the body is concentrated on a minimal support base of the heel and toes (Cohen & LaRue, 2005). Often, the cause of a fall is not so much the absolute value of friction but, rather, an unexpected change in traction. When pedestrians expect or realize that the surface they will traverse is slippery (such as when walking on ice), they can adjust their gait accordingly. Typically, they take shorter strides and maintain a sturdier base with the center of gravity over their feet. However, when the traction of the floor surface changes unexpectedly, the pedestrian might not be able to make those necessary gait changes. Common examples of slip incidents are when floors are wet from cleaning, rain, or spills or when transitioning from one surface to another, such as from carpet to a smooth floor. The coefficient of friction (COF) is the ratio of the force required to move one surface over another and the total force pressing the two surfaces together. Two types of COF are often described: static and dynamic. The static COF relates to the force required to initiate a movement of two surfaces over each other. The dynamic COF refers to the force required to keep two surfaces moving over each other once the motion is initiated. In the early 1940s, the Underwriter’s Laboratories concluded that a static COF of 0.5 was the minimum allowable for a floor polish to qualify for the UL seal. In 1953, the Downloaded from rev.sagepub.com by guest on September 6, 2012


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Federal Trade Commission also recommended the standard of 0.5. Since that time, walking surfaces with a COF less than 0.5 have not been considered slip resistant (Johnson, 2005). This issue has been reexamined, and the 0.5 minimum has been verified (i.e., Sacher, 1993). When tested with a flat sole of a shoe on ice, a COF of less than 0.20 is usually measured. Dry and clean asphalt may have a COF of 0.80 or higher (Johnson, 2005). In order to avoid slips, areas should be designed with uniform and high-traction flooring surfaces throughout. Premises should be maintained so that pedestrians do not come upon unexpected floor surface changes that may precipitate a slip. Floor cleaning should be done when people are not expected to be present or in conjunction with conspicuous hazard cones that make it clear that the floor may be wet in a specific area. Stairway design. Extensive research has been conducted to determine the best configuration for the design and construction of stairs (Templer, 1992). Falls with serious injuries are much more likely when descending rather than climbing stairs. Although it is possible for a person to trip while ascending stairs, the injuries that occur on descent are typically more severe. When descending, a person will typically fall because of a misstep of the foot as it moves down to the next step. Possible causes for a misstep include irregular stair geometry, obstacles, fluid or ice, perception issues, and inattention (Johnson, 2005). Typically, pedestrians look at their path at the beginning and end of the flight of stairs (Templer, Archea, & Cohen, 1985). Once a gait is established for a set of stairs, it is usually maintained without the need to look down at the steps. Irregular stair design creates a hazard by violating the expected gait of the person ascending or descending the stairs. This gait is based on the expectation that the stairs will be uniform in dimensions (Cohen & LaRue, 2005). In addition, these dimensional changes are rarely easily discernible. Because differences in stair geometry can lead to a loss of balance and a fall, building codes generally allow only a 3/8-inch maximum variation in riser height and tread depths for a given stairway. It is important that stair users be able to easily see the physical elements of stairs—particularly the nose, or leading edge, of the step tread. The step nose may be difficult to see because of lighting conditions or floor covering materials that have a camouflaging effect. This means that the steps are not easy to distinguish from surrounding colors, patterns, or textures (Johnson, 2005). These visibility problems make it more likely a person will overstep the nose, which often results in a fall forward. The only way it may be possible to prevent a fall forward after a loss of balance is by accessing and holding on tight to the handrail. However, holding onto a handrail will not always prevent a fall after one loses one’s balance; it may simply slow the fall or alter the point of rest. Slipping on a stairway is also possible. As the foot lowers to the next step, an insufficient coefficient of friction could result in the foot slipping off the intended step and a resultant loss of balance and possible fall. Nonslip stair treatments such as textured tape at the step nose are very effective in increasing the COF and preventing slips off stairs. Conscientious maintenance of nonslip stair treatments is crucial if it is to maintain its effectiveness. Evaluating the thoroughness of the floor maintenance and inspection program is important when performing an HF analysis of stairway incidents.


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Private Places The same types of accidents that occur in public places can also occur in private places such as homes. Because a limited number of people live in a given private residence, uniform building codes may differ from those that apply to public places. HF consultants need to be familiar with which codes apply to a given context. When investigating incidents that occur in private places, forensic HF professionals consider relevant codes as a basis for opinions regarding standard of care. Although HF experts are not called upon to interpret local, state, or national building codes and their application to a specific location, they can cite these standards as a basis for an opinion.

Workplaces Forensic human factors experts may be asked to analyze worker’s compensation cases that appear to be work related. Employees who are injured at work typically do not have the right to sue their employer for damages relating to the injury. Instead, they must use the worker’s compensation system if the injury is attributed to a work-related incident. Between 1910 and 1949, all U.S. states enacted a workman’s compensation law, which was later renamed “worker’s compensation” in some states to maintain gender neutrality (U.S. Chamber of Commerce, 2002). The basic worker’s compensation test of causation for an injury or disease is whether the injury resulted from and occurred in the course of employment. When workers are injured by a machine or at an off-premises location, they may be able to bring suit against the product manufacturer or the owner of the premises involved. Some states have recently opened a loophole that allows an employee to collect worker’s compensation benefits and sue his employer. In this instance, the employee must prove his injury was caused by the employer’s having knowingly engaged in some form of bad conduct, referred to as egregious conduct, gross negligence, or wanton disregard for employee safety, depending on the jurisdiction (Jenson & Bricio, 2005). These are legal terms that may be relevant to some investigations but not appropriate for any expert to use if they are outside the expert’s technical area. Injuries covered by worker’s compensation are usually those resulting from accidents, including unexpected events such as overexertion and falling. Diseases covered by worker’s compensation are usually medical conditions resulting from exposure to various workrelated substances, such as hazardous chemicals or infectious agents (Jenson & Bricio, 2005). Workstation/equipment design. On the job, people are frequently required to interact with systems, equipment, machinery, and tools without any thought by employers to the fit between the person and the environment. As a consequence, workers are sometimes injured as a result of performing their required job tasks. When a cumulative trauma disorder occurs at work, it is necessary to analyze the work environment to determine what features of the workplace or work tasks contributed to the injury. In one case, a telemarketer sued an employer for a cumulative trauma disorder based on the claim that the workstation design and management controls were Downloaded from rev.sagepub.com by guest on September 6, 2012


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inadequate. In this case, the HF expert evaluated the employee’s workstation and task demands to determine if they were causal factors in the incident. The evaluation indicated that the employee was not making use of the adjustable features of the workstation and, further, was not taking the breaks allowed by the employer. In cases such as this one, the HF expert might be asked to provide an opinion about whether such equipment adjustments or rest breaks would have reduced the likelihood or severity of the injury experienced by the worker. Task demands and stress. The preferred approach to minimizing injury risk is to design tasks so that the demands are within the capabilities of a high percentage of the workers (Dempsey, 2005). Task assignments, work goals, and the allotted time to perform tasks are often important aspects of employment. Work stress frequently occurs when these elements are not perceived by the worker as reasonable. Stress is an important variable that affects perception and decision-making ability. High stress typically occurs when the time to perform a task is limited or when too much information needs to be processed (Helander, 2005). High stress also occurs when employees view their responsibilities as having life-or-death consequences, as in the medical field. When high stress levels occur on the job, workers often have difficulty considering information outside their primary focus that may be important to the task at hand. This increases the probability of operator error (Helander, 2005). Work overload can be a persistent source of stress when employees must process complex information and make difficult decisions. Quantitative overload occurs when an employee is given too much to do in a specific period. Qualitative overload refers to when the task is too difficult for the employee’s abilities. When the workload is in balance with the worker’s abilities and knowledge, stress often has a positive impact on job performance. However, when task demands exceed the employees’ abilities (overload) or fails to challenge them sufficiently (underload), people experience stress negatively (Cummings & Worley, 1993). Multiple variables determine the appropriateness of given task demands and work schedules and the degree to which these factors place workers at risk. If task demands and stress are relevant factors in a work-related investigation, a systematic analysis by an HF expert may be needed to assess the interacting factors (Tepas, 1999). For example, a delivery driver who gets into an accident because his work required him to answer phone calls, radio calls, wayfind, and drive all at the same time may have been exposed to overload.

Code Application Codes and laws are legal requirements governing a particular jurisdiction. In the United States, a number of building codes can be adopted and enforced by any jurisdiction, and there is no single code that regulates the entire country. In total, more than 40,000 political jurisdictions in the nation adopt or enforce modern building codes and standards that help to ensure public safety (Galley, 2005). HF experts use these codes as a basis to support their opinions concerning standard of care when they believe that the subject situation does not conform to potentially applicable codes or laws and that this deficiency was a causal factor in the incident at hand (Cohen & LaRue, 2005). Examples of relevant and Downloaded from rev.sagepub.com by guest on September 6, 2012

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often-cited codes include the International Building Code (IBC) and Uniform Building Codes (UBC). The Federal Americans With Disabilities Act (ADA) is not a building code and will be addressed in the next section. Note once again that it is typically not the expert’s responsibility to know which codes apply to a given jurisdiction, as that is a legal issue. Voluntary consensus standards are those that have been developed by committees associated with standards-setting bodies through an industry consensus process. These standards are not legally binding, but they are usually well known throughout the given industry, as they typically describe design and safety features for that industry (Cohen & LaRue, 2005). Often, experts utilize these voluntary consensus standards as a standard of care for the case they are analyzing. This means that although compliance with standards is not at issue, there is still a deviation from what has been determined safe by the industry standard-setting committee. In other words, the voluntary standards are not arbitrary and baseless; they are based on what practitioners in the various fields agree upon as being appropriate. Examples of organizations that establish voluntary consensus standards include the American National Standards Institute (ANSI), the American Society for Testing and Materials (ASTM), the International Standards Organization (ISO), and Underwriter’s Laboratory (UL). Sometimes, consensus standards are adopted by regulatory bodies, at which time they become mandatory rather than voluntary.

Americans With Disabilities Act (ADA): Accessibility When people with disabilities are involved in an incident that results in litigation, the HF expert must consider guidelines set forth in the ADA. In July 1990, the ADA was signed into law and became effective in July 1992. The main purpose of the ADA is to provide comprehensive civil rights protection to people with disabilities. The ADA provides guidelines that support a national mandate to increase accessibility and eliminate job discrimination against people with disabilities. This includes making sure that all public buildings are accessible to people with disabilities and ensuring that qualified people with disabilities are given employment opportunities. According to the ADA, a disabled person is an individual who has a substantial physical or mental impairment that limits a major life activity (e.g., hearing, walking, feeding oneself). In the workplace, employers cannot discriminate against a qualified person with a disability. The term qualified means the person can perform the essential job functions with reasonable accommodation. According to the Code of Federal Regulations, a reasonable accommodation for employees may include the following: 1. making existing facilities used by employees readily accessible to and usable by people with disabilities and 2. job restructuring, part-time, or modified work schedules, acquisition or modification of equipment, and modifications of testing done to satisfy the employee’s unique set of abilities.

The ADA is a civil rights law, not a building code. There are no building inspectors to verify compliance with the ADA. It is enforced through litigation when complaints are filed through the Department of Justice. Downloaded from rev.sagepub.com by guest on September 6, 2012


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Not all litigation regarding disabilities is filed in federal court; thus, HF experts may address the ADA as a standard-of-care issue for personal injury or as accessibility cases filed in the state courts. For cases involving individuals who are protected under the ADA, the expert can address the ADA requirements as design features that make the environment more accessible. Of course, experts are also retained in matters litigated through the Department of Justice expressly as ADA matters. Examples of ADA-related cases in which an HF expert might be retained concern accessible public areas (see Figure 3.1), workplaces, wrongful termination, or a trip-and-fall case in which a person with a disability is injured. Forensic HF consultants may also be asked to evaluate the accessibility of different facilities by builders and developers who are sometimes sued by the Department of Justice for violating accessibility standards. The ADA Accessibility Guidelines (ADAAG) can be used in all these cases to support the expert’s opinions. An expert working on a housing case involving, for example, an apartment complex can invoke both the ADAAG and the Fair Housing Act. The common areas (recreation rooms, swimming pools, parking, walkways, etc.) are covered by the ADA, whereas the private housing units are covered by the Fair Housing Act.

PRODUCTS Consumer products are ubiquitous and present a challenge to manufacturers who want to ensure safety and effectiveness (Boehm-Davis, 2006). New technologies have provided a multitude of products intended to improve quality of life, simplify tedious tasks, and provide recreation. Although these products are designed to be—and often are—helpful and useful for a particular task, their design may also result in injuries to users. Injuries could be attributable to misuse of the products, failure to follow instructions and heed

Figure 3.1. Many jurisdictions now require parking lots to have curb cut ramps instead of built-up ramps (seen here) because of the hazard created by the side slope. Downloaded from rev.sagepub.com by guest on September 6, 2012

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warnings, or use of the product in a manner that is unintended and unanticipated by the manufacturer (Vredenburgh & Zackowitz, 2005). When a product is designed in such a way that it can cause injury or death when used as instructed or in a foreseeable misuse, the manufacturer may be held liable for damages associated with use of the product. HF experts are often asked to investigate accidents as part of product liability litigation. An HF consultant provides expertise concerning specific design features, the product design process, labeling, and instructional characteristics of the product, as well as the interaction between the user and the product. Specifically, HF experts try to answer how, if at all, the product contributed to the incident (Vredenburgh & Zackowitz, 2005). Manufacturers and distributors are legally responsible for managing and communicating product risk information to consumers. When the design of a consumer product is implicated as the possible cause of an injury or death, it is important to determine what the manufacturing company knew about the risk and when it was known (Statler, 2005). HF experts typically deal not with a manufacturer’s legal duty but with the company’s responsibility to share information that it knew or should have known when an incident occurs.

Consumer Products Accidents involving consumer products range from toys with easily removable parts, to vehicles with faulty gauges, to tools with improper or incomplete instructions. When forensic HF experts are asked to investigate incidents involving a consumer product, they often evaluate how risk to users was managed in the development and marketing of the product. The primary hazard control strategy, sometimes referred to as the forensic accident analysis model (Askren & Howard, 2005) includes, in order of preference and effectiveness, (a) designing hazards out of the product, (b) guarding against hazards, and (c) providing warnings and instructions related to hazards. Product design. Ideally, a product should be designed at the outset to prevent unsafe behaviors from occurring during its use (Boehm-Davis, 2006). Once a manufacturer (or others in the product supply chain) become aware of a product hazard, they have a legal duty to do something to minimize the risk that the hazard will injure product users. Removing a hazard through design changes is the least expensive and most effective method of dealing with it. Removing a hazard through design can be done at any point in the product development process, but it is best done as early in the process as possible (Vredenburgh & Zackowitz, 2005). This provides an incentive to have an active risk analysis process in place so potential hazards can be identified during the first stages of design (Vredenburgh & Zackowitz, 2005). Because such a broad range of consumer products is available, there is no single design approach that will eliminate all hazards for all products. For example, consider the placement of controls for a stove. People who use wheelchairs need to have them in the front of the unit, within easy reach. However, parents of young children typically want the controls at the rear of the unit, out of reach of the children. During a forensic analysis, what is important is determining the adequacy or inadequacy of the product design as it relates to the incident at hand (Askren & Howard, 2005). Downloaded from rev.sagepub.com by guest on September 6, 2012


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Unfortunately, hazards are not always identified and removed during the development process. Sometimes products with hazards are marketed and sold before the hazard becomes evident. When this occurs, manufacturers are typically faced with a very expensive product “fix” process. If the risk of injury from the hazard is high enough, manufacturers can be forced to recall the affected products. Product recalls are fairly common for products such as children’s toys, but other products are recalled too, such as prescription drugs, tires, automobiles, and clothing items. Product recalls are a very expensive proposition for manufacturers; a single product recalled by a manufacture can easily cost millions of dollars (Booker, Raines, & Swift, 2001). HF experts are not recall experts. They would not opine regarding whether a recall should have been implemented or would have prevented an incident. Their role in product liability matters is in evaluating the product and the manufacturer’s responsibilities to the consumer. This may include communication issues that are relevant to product recalls. For example, in one case, a manufacturer was sued when it did not recall a faulty toilet that it knew could cause injury or property damage to users. The manufacturer had the hazard information and failed in its responsibility to share that information with consumers. Guarding. Sometimes a product has hazards associated with its use that cannot be eliminated through design changes. This is often the case with products—tools, for example—that have mechanical or electrical hazards. Some products (e.g., power saws and common kitchen knives) are intended to cut through materials, so it is not possible to design out the sharp blade hazard without rendering the products useless. When the hazard associated with the product cannot be eliminated through design changes, manufacturers typically move to the second tier of the hazard control hierarchy and address the hazard with barriers or guards. Barriers typically consist of a physical wall or other component separating the user from the hazard. On saws, a plastic blade guard is often included in the product design to separate the user from the blade (Vredenburgh & Zackowitz, 2005). Guards are often placed over switches to prevent inadvertent activation of a power source or placed over other moving parts of a machine to prevent accidental contact with an article of clothing or part of the body. Guarding can also be accomplished by arranging components in a particular way. For example, stamping and cutting machines often require the simultaneous activation of two switches placed far enough apart to require the use of both hands. This reduces the possibility that users will place one of their hands in a pinch or crush point. Legal cases that deal with guarding issues often involve manufacturing or agricultural equipment use. Issues may involve reasonableness of conduct if a worker removed a guard or did not follow proper work procedures, or the manufacturer may not have designed an effective guarding system. If a manufacturer designs a product with appropriate and effective guards, it is the user’s responsibility to use them. Sometimes users remove guards from equipment, machines, and products because the guards are viewed as bulky or awkward. When the user removes a guard or otherwise alters the product such that the guard does not effectively protect against the hazard, he or she is assuming the risk associated with the hazard exposure. Downloaded from rev.sagepub.com by guest on September 6, 2012

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Warnings/instructions. If manufacturers are going to market and sell a product with a hazard that has not been eliminated through design or physical guarding, they need to go to the third tier of the hazard control hierarchy: an effective hazard-warning system (e.g., Figure 3.2). Warnings apply to all types of consumer products and in recent years have become a key forensic HF issue. An extensive review of the characteristics of effective warnings is provided in a chapter by Laughery and Wogalter in the current review series (Volume 2, 2006). The manufacturer is generally considered to have the greatest expertise about risks associated with its products, whereas the consumer is typically considered less informed (Laughery & Wogalter, 2005). Manufacturers have a duty to warn of a hazard when the product is dangerous, the hazard is or should be known to the manufacturer, the hazard is not obvious to the user, and the hazard is not caused by the product’s being put to some unforeseeable use (Madden, 1999). Manufacturers have an obligation to provide warnings sufficient to permit a product to be used safely or for the consumer to make an informed decision not to use the product. In fact, a product is considered to be legally defective if it has instructions or warnings that are inadequate and, if improved, could have reduced or avoided risk of harm (Restatement of the Law, 1998, Third Section 2[c], p. 14). Therefore, it is in the manufacturer’s best interests to provide useful and complete warning information. When HF experts evaluate a case that has warnings issues, they must consider whether a warning was needed, if it was adequate, and whether the warning would have made a difference in the outcome of the product interaction (Laughery & Wogalter, 2005). The HF expert must first determine whether a hazard existed. If there was no hazard or if the hazard was considered open and obvious, there is no legal or technical duty to warn. If a product hazard existed, the HF expert must determine whether a warning was necessary and, if so, if it was present and adequate. In determining warning adequacy, the expert must consider all warnings related to the product, including on-product and inmanual warnings.

Figure 3.2. When products have hazards associated with them that cannot be designed out or guarded against, a communication system (warning) is used, as seen in this laundry dryer. Downloaded from rev.sagepub.com by guest on September 6, 2012


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ANSI Z535 (2002) is the standard most often used to evaluate the adequacy of warnings. This standard consists of five parts, 535.1 through 535.5. Three parts (535.1, 535.3, and 535.4) are particularly applicable to consumer products and address colors, symbol/ icon design, and the overall layout of warnings, respectively. If product warnings were needed and present, the HF expert must determine if changes to the warning system would have resulted in a different outcome for the target incident. If the warnings are considered inadequate but not directly related to the incident, then changes to the warning would have no effect (Vredenburgh & Zackowitz, 2005). Although well-written warnings probably will not achieve 100% compliance, a substantial amount of evidence indicates that, in many circumstances, warnings can be very effective in informing product users and eliciting self-protective responses (e.g., Wogalter, Allison, & McKenna, 1989). Warnings cases may involve a multitude of different types of products; for example, medical devices such as latex gloves that can result in allergic reactions, laundry units that can spontaneously combust, and air guns used for paint pellets. These are examples of products that have hazards associated with their use that manufacturers know about and should thus warn consumers about. Foreseeable misuses. Manufacturers have to consider both the intended uses and the foreseeable misuses of their products. For example, a playground slide is designed so children can climb up to the top of the slide and then slide down. Typically, slides include steps or a ladder to reach the top of the slide. However, children often walk up the chute part of the slide. This behavior is considered a foreseeable misuse of the product that designers and manufacturers must consider when assessing potential product hazards. Electrical plugs and outlets are typically designed so that users cannot insert plugs with an incorrect orientation. However, this commonsense hazard elimination approach is not always taken (see Figure 3.3). Identifying foreseeable misuse can be accomplished by using a structured risk analysis process or, at minimum, by thinking through mistakes that

Figure 3.3. This plug was not designed with foreseeable misuse in mind. The user plugged it in incorrectly and was electrocuted. Downloaded from rev.sagepub.com by guest on September 6, 2012

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might arise from the user’s perceptions, cognition, attention, and expectations (Wardell, 2005). One procedure for predicting foreseeable misuse has been proposed by Askren (2005). An example of a case in which foreseeable misuse is at issue involves the use of an infusion pump in a hospital setting (Morrow, North, & Wickens, 2006). These devices allow controlled delivery of pain medication. Under conditions of time pressure and heavy workload, it is foreseeable that a nurse may be rushed while inputting data into an infusion pump. Therefore, these devices should be designed with a “fool-proof ” programming system.

Work Equipment Despite the creation of the Occupational Safety and Health Administration (OSHA) in 1970, which was established to reduce work-related accidents, occupational injury rates remain high. For example, approximately 5,000 people died during 2006 in work-related incidents (National Safety Council, 2008). Industrial accidents often involve work equipment that employees are required to use. When incidents occur on the job, factors such as training and supervision must be considered and evaluated by forensic HF experts, in addition to the hazard control hierarchy previously discussed. Training. Training can be defined as the systematic acquisition of knowledge, skills, and abilities that leads to improved performance in a particular environment (Salas, Dickinson, Converse, & Tannenbaum, 1992). In order to develop an effective and appropriate training program, the tasks that an employee needs to perform first must be identified. A job and task analysis (JTA) is a useful tool for this purpose. Job and task analysis is a process that breaks down jobs into specific tasks to determine the behaviors, skills, information, and other resources necessary to perform a given job function. A JTA may be involved in any incident in which an employee claims he was injured on the job. For example, a JTA would be useful in determining if an injury is consistent with the type of tasks an employee is required to perform. If a particular job includes working with products such as chemicals or equipment, the employee must be trained on their proper use. This training should include avoiding misuse that could lead to injury. In other words, the employee must be trained how to do her job safely—for example, by learning how and when to use personal protective equipment, proper postures for computer work, and proper tools. When investigating an incident that occurs on the job, the forensic HF expert must analyze the employee’s training, including the duration and type of training, the topics that were covered, testing on curriculum content, and assessment of the transfer of training to the actual job. It is essential for employers to document employee training, because such documentation is the primary method of verifying that specific training has actually been delivered. This analysis will allow the HF expert to determine whether the employee’s training was both adequate and pertinent to the incident being analyzed. Supervision. As part of an HF evaluation of a workplace incident, supervisory practices are sometimes relevant, as it is often up to supervisors to ensure that employees are complying with safe work practices. For example, suppose an employee had been Downloaded from rev.sagepub.com by guest on September 6, 2012


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admonished previously for the improper use of a piece of equipment but continues this unsafe behavior and is subsequently injured. The employer has a stronger defense if it can show that the employee was trained adequately and his high-risk behavior had been previously identified and corrected. Equipment design. In industrial settings, the issue of equipment design includes user interface(s) of specific equipment, as well as the overall layout of the shop floor or other industrial space in which employees are required to work and move. Workers who use traditional computer workstations are at risk for repetitive strain injuries if their workstations are not adjusted appropriately. In the organizational arena, adjustable workstations are an excellent design option so that each workstation can be adjusted to fit individual employees. In particular, chair height, desk height, keyboard/mouse position, and monitor height and depth are important workstation adjustments. Sometimes organizations choose to perform proactive workstation evaluations by qualified ergonomics and HF consultants. This is a cost-effective way to ensure that employees are working in appropriate settings.

SUMMARY When a lawsuit has been filed, forensic HF consultants may be able to help the parties analyze the incident and identify pertinent human factors issues. By learning how the features of the person, place, or product involved in the case were factors in the incident, attorneys may be able to settle a case without going to trial. In this chapter, we have provided a brief introduction to the role HF consultants play, the procedures that they typically follow, and many of the most common issues addressed in forensic HF cases.

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