Detecting Deception Via Strategic Disclosure of Evidence - Springer Link

C 2005) Law and Human Behavior, Vol. 29, No. 4, August 2005 ( DOI: 10.1007/s10979-005-5521-x

Detecting Deception Via Strategic Disclosure of Evidence 1 ¨ Anders Granhag,1 Leif A. Stromwall, ¨ Maria Hartwig,1,3 Par and Aldert Vrij2

Deception detection research has largely neglected an important aspect of many investigations, namely that there often exists evidence against a suspect. This study examined the potentials of timing of evidence disclosure as a deception detection tool. The main prediction was that observers (N = 116) would obtain higher accuracy rates if the evidence against the suspects (N = 58) was presented in a late rather than early stage of the interrogation. This prediction was based on the idea that late evidence disclosure would trigger lack of consistencies between the liars’ stories and the evidence; this could be used as a cue to deception. The main prediction received support. Late disclosure observers obtained an overall accuracy of 61.7%, compared to 42.9% of Early disclosure observers. Deceptive statements were identified with high accuracy (67.6%) in Late disclosure, indicating that the technique in this form is beneficial mainly for pinpointing lies. KEY WORDS: interrogation; deception detection; evidence.

For more than three decades, researchers have systematically explored human deception detection ability. The major finding is that people, both lay persons and presumed lie experts working within the legal field, are not very skilled in distinguishing between truthful and deceptive statements, with hit rates generally around the level of chance (Kassin, 2004; Meissner & Kassin, 2002; Vrij, 2000). Research attempting to examine presumed lie experts’ ability to detect deception has neglected one important aspect: in many investigations there is evidence against the suspect in question. In this study, we will test the idea that the case evidence, if handled strategically during the interrogation, has the potential of being a powerful tool in the process of detecting deception. Identifying such a tool would be a step forward in a constructive direction for the deception detection domain. A few studies have conducted analyses of real-life interrogations, and analyzed when the evidence is disclosed during the interrogation (Leo, 1996; Moston 1 Department

¨ of Psychology, Goteborg University, Sweden. of Portsmouth, UK. 3 To whom correspondence should be addressed at Maria Hartwig, Department of Psychology, Goteborg ¨ ¨ University, P.O. Box 500, SE 405 30 Goteborg, Sweden; e-mail: [email protected]. 2 University

469 C 2005American Psychology-Law Society/Division 41 of the American Psychological Association 0147-7307/05/0800-0469/1

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¨ Hartwig, Granhag, Stromwall, and Vrij

& Engelberg, 1993). These studies have shown mixed results. In an American study, this disclosure of evidence, often together with a suggestion of guilt, was the typical way to start the interrogation, and occurred in more than 80% of the cases (Leo, 1996). Moreover, some American police interrogation manuals recommend that an interrogation should be started by confronting the suspect with the existing evidence (e.g., Yeschke, 1997). In contrast, in a British study (Moston & Engelberg, 1993), it was found that only a minority of interrogators (slightly above 12%) disclosed the evidence to the suspect at the beginning of the interrogation; this sometimes occurred in connection to an explicit guilt accusation. The scholars that have examined when evidence is introduced argue that disclosing the evidence at an early stage of the interrogation is not recommendable, since this practice can lead to false confessions not being detected (Moston & Engelberg, 1993). For example, if a suggestible suspect is presented with the details about the available evidence during an interrogation, and this suspect provides a false confession to the crime in question, it may be difficult to know if the details included in the confession are derived from a real memory, or from the interrogation in which the evidence were disclosed to the suspect. We agree with the idea that disclosing the evidence at the outset of an interrogation could be risky. However, in this paper we argue that there may be more benefits of refraining from disclosing the evidence in an early stage of the interrogation. Simply put, refraining from disclosing the evidence at the outset of the interrogation could plausibly be a deception detection technique, because providing late evidence may reveal inconsistencies in liars’ statements or notorious gaps in their statements. These inconsistencies and gaps could subsequently be used as tools for detecting deceit. Note that refraining from disclosing the evidence is not the same things as refraining from informing a person of being suspected of a crime. One can very well inform a person that he or she is a suspect without providing the person with information about the evidence. Suspects’ strategies. If all the evidence against a suspect is presented at an early stage of the interrogation, a suspect will know what he can and cannot say in order not to contradict the case-specific knowledge the interrogator has. For example, if some evidence binds the suspect to the scene of the crime, and this information is given to the suspect in the beginning of the interrogation (e.g., “You are suspected of murdering John Smith. There is no point in denying, because we found a hair from you at the scene of the crime.”), the suspect will probably refrain from saying that he has never been to the place where the crime occurred. Instead, he might say that he was at the place, but did not do anything illegal. When the suspect’s statement is consistent with the evidence (i.e., the suspect does not contradict the potentially incriminating information, instead he makes the case-specific information less useful by merely giving an explanation for the existence of this information), the interrogator is left with less valid aspects of the demeanor of the suspect to rely on when assessing veracity. The situation in which the lie-catcher has access to only these aspects of demeanor as a basis for lie detection mirrors most of the deception detection studies conducted so far; and, as mentioned earlier, people are not very skilled in detecting deception in these situations (Kassin, 2004; Meissner & Kassin, 2002; Vrij, 2000).

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In contrast, we believe that more cues may surface when the interrogator refrains from disclosing the evidence to the suspect until the end of the interrogation. When the guilty suspect does not know about the evidence the interrogator has against him, there may be lack of consistencies or outright inconsistencies between his statement and the information held by the interrogator. How would this lack of consistency come about? In the recent meta-analysis by DePaulo and her colleagues, it was predicted that liars would offer fewer details, partly because that would allow for fewer possibilities to be disproved. This prediction was supported by the results (DePaulo et al., 2003). This idea was also supported by a study on liars’ and truth tellers’ strategies, where it was found that liars interrogated by experienced police officers reported trying to keep their story as simple as possible ¨ in order to be judged as truthful (Stromwall, Hartwig, & Granhag, in press). In the meta-analysis, it was also argued that lies may be especially more brief and less detailed than truths when people are asked to tell a story rather than asked to respond with just a few words (DePaulo et al., 2003). Hence, in response to a request for free recall (in an interrogation where the suspect is unaware or unsure of the evidence against him), one could expect more omissions in a liar’s story than in a truth teller’s for three reasons: (1) liars do not want to risk being disproved; (2) producing a deceptive story may in some cases be more cognitively demanding than telling a truthful one, resulting in fewer details, and (3) if the interrogator does not mention any evidence, the suspect can be led to think that there is none (or only very weak evidence); in such a situation it would not be risky to simply omit details that may seem incriminating. Thus, in response to this late evidence disclosure technique, liars’ stories may lack consistency with this evidence due to omissions of details, or may even contradict this evidence. There is reason to believe that the innocent suspects will react differently to the late evidence disclosure technique. Research has identified a phenomenon labelled the illusion of transparency, which is the tendency to overestimate the extent to which others can read one’s internal states. This tendency has been observed among other things when people are lying; they then overestimate the detectability of their lies (Gilovich, Savitsky, & Medvec, 1998). This tendency also implies that an innocent suspect indeed will tell things like they happened without holding information back, since he or she tends to believe that an interrogator can read his or her internal state, and thus correctly realize that the statement indeed is true. Support for the suggestion that innocent suspects will tell the truth to an interrogator without withholding information was found in a recent study which examined the strategies adopted by mock suspects for being perceived as credible ¨ (Stromwall et al., in press). Observers’ strategies. Plausibly, the late evidence disclosure technique will result in lack of consistencies (i.e., more omissions or inconsistencies) for guilty suspects, while innocent suspects will be more prone to give information to the interrogator. To what extent will lie-catchers be able to detect these possible inconsistencies exhibited by the liars? It should be noted that there are several different types of verbal inconsistencies that may be used when assessing veracity. For example, there may be inconsistencies in a suspect’s statement within the same interrogation (Greuel,


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¨ 1992), or inconsistencies from one interrogation to another (Granhag & Stromwall, 2002). Moreover, there may be inconsistencies between two or more suspects who ¨ are believed to be involved in the same crime (Granhag, Stromwall, & Jonsson, 2003). For the present study, we are interested in a fourth type, namely inconsistencies between the suspect’s statement and the evidence pointing to his guilt. Research has shown that lie-catchers have a pronounced tendency to rely on consistency, or lack thereof, if this cue is available.. Both studies on people’s beliefs ¨ ¨ about cues to deception (e.g., Granhag & Stromwall, 1999; Stromwall & Granhag, 2003), and studies on the basis for veracity judgments (Greuel, 1992), indicate that people believe that lack of consistency is a cue to deception. In summary, the core of the late evidence disclosure technique is that it can trigger lack of consistencies in the stories of the guilty suspects. Plausibly, lie-catcher will use this lack of consistency as a basis for their veracity judgment, which may lead to a relatively high deception detection accuracy. In the present study, we have tested these ideas experimentally. Hypotheses Hypothesis 1. Observers watching a person either guilty or innocent of a mock crime (hence either lying or telling the truth) would obtain higher deception detection accuracy if the evidence against the suspect was presented late in the interrogation rather than early. In other words, if any of the accuracy scores would exceed the level of chance, it would be most likely to be in the Late disclosure condition. Hypothesis 2. When the evidence was disclosed early in the interrogation, both liars and truth tellers would include this evidence in their free recall statements to the same extent. However, in the Late disclosure conditions, liars, more than truth tellers, would refrain from providing much information in their free recall, which would make it more likely that they would omit information about the parts of the event concerning which the interrogator had evidence. Regarding the specific questions phase, we predicted that liars’ statements would be more inconsistent with the evidence, in particular when this evidence was disclosed late. Hypothesis 3. Observers watching Late disclosure would report relying on verbal content to a higher extent than would observers watching an interrogation in which the evidence was presented early. We believe it is reasonable to assume that the observers will attend more to the verbal content of the message when there are inconsistencies with the evidence. When fewer of these inconsistencies can be expected to arise, the observers will be less concerned with the verbal aspects of the statements. METHOD Overview The experiment was carried out in three phases and used a mock crime and interrogation paradigm introduced by Kassin and Fong (1999). In the first phase,

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college students were instructed to either commit a mock theft or a non-criminal act. Second, they were interrogated according to one of two interrogation styles (in one of these the evidence was disclosed in the beginning of the interrogation, in the other the evidence was disclosed at the end, see further descriptions below); these interrogations were video-taped. In these interrogations, the participants who had committed the mock theft were instructed to lie about the event and construct a story where they carried out a non-criminal act, while the participants who had committed the non-criminal act were asked to tell the truth about what had happened. In the third phase, these video-tapes were shown to a number of college students who were asked to determine whether the suspect was guilty or innocent of the mock theft. Design. The experiment had a 2 (Evidence disclosure: Early vs. Late) × 2 (Veracity: Truthful vs. Deceptive) between-group design. Phase 1 Participants. The group of participants acting as suspects consisted of 64 undergraduate students (43 females and 21 males, age ranging from 19 to 63 years, ¨ M = 26.3 years) from Goteborg University. These students were recruited on a voluntary basis, and were given a lottery ticket as a compensation for their participation. They were told that they could receive two more tickets if they managed to convince the observers of their video-taped interrogation that they had not committed the crime. This was explained to them in detail before they took part in the interrogation. Procedure. When the participants arrived to the Department of Psychology, they were randomly allocated to one of the two veracity conditions (either truthful or deceptive). The participants in the deceptive condition were asked whether they had any objections against committing a mock crime in a nearby video store; six participants (all females) out of 32 did and were therefore reallocated to the truthful condition. However, their data were not further analysed, and all analyses were based on the remaining 58 participants. The participants in the truthful condition (N = 25) were instructed to go to a movie store near the Department and look for a specific DVD-movie in a box in one corner of the store. They were told that they could keep the movie if they found it (it was stressed to them that this would not be a theft since the DVD-movie had already been paid by the experimenter), and to show it to the shop assistant before bringing it with them to the Department. If they did not find it after a minute of searching, they were to return to the Department. In fact, the movie was not there at all, hence all truth tellers were in the store for a couple of minutes and left empty-handed. Importantly, on top of the box in which the participants were instructed to search for the movie, a briefcase had been placed. This briefcase was slightly opened, and had a wallet partly sticking out of it. The participants had to move this briefcase while looking for the movie in order to get a proper look in the box. The participants assigned to the deceptive condition (N = 33) were instructed to go to the same movie store and steal the wallet from the briefcase on the box filled with DVD-movies. They were instructed to pretend to be looking for a movie and


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to steal the wallet when they thought no-one was looking. After putting the wallet in their pocket, they were to return to the Department. A number of precautions were taken in order to protect the deceptive participants from being perceived as real thieves by other customers. First, the shop assistants in the video store were informed that an experiment was taking place, and that no real theft occurred. Second, as will be discussed below, there was an undercover experimenter in the shop who among other things had the task to inform any visitors who witnessed the theft that it was part of an experiment. Third, the experiment did not take place during the hours when the store had the most visitors. In both the truthful and deceptive condition, participants were watched by two undercover experimenters while in and outside of the movie store. One experimenter was standing outside of the store pretending to wait for someone and hence checked that the participants did enter the store. The other experimenter was standing a few meters from the box in which the briefcase was placed; this person controlled whether the participants in the truthful condition in fact moved the briefcase (everyone did), and whether participants in the deceptive condition stole the wallet from the briefcase (everyone did). As will be explained in greater detail below, the presence of these experimenters was also used as an evidence in the subsequent interrogation of the participants. After taking part in the event (either the mock theft or the non-criminal act), all participants were sent home, after having made an appointment with the experimenter to come back in one week for the interrogation. The reason for this time-lag was that we wanted to simulate a real-life investigation as much as possible. Phase 2 Pre-interrogation instructions. All participants returned to the Department of Psychology after one week, and were then provided with instructions for the upcoming interrogation. Both liars and truth tellers were told that a wallet had been stolen from a briefcase in the video store located near the Department. They were told that they were suspects in the investigation (henceforth, all these participants are referred to as suspects), and that the investigators had information about the fact that they had visited the video store on the day of the theft. The suspects were told that the interrogator they would encounter did not know whether they were guilty or not, and that their main task was to act as convincingly as possible. Truth telling suspects were instructed to give a truthful account during the interrogation, while lying suspects were asked to lie about the fact that they had committed the mock crime. Both truth telling and lying suspects were told that the interrogation was to be video-taped and shown to a number of people whose task was to assess their veracity. If they managed to convince a majority of them that they were telling the truth, and thus had not committed the theft, they would receive two lottery tickets (together with the one that they were guaranteed to receive). The liars were instructed to tell the interrogator that they had visited the video store in order to look for a movie (“Make up a story in which you say that you were in the video store to look for the movie Casablanca on DVD”). No instruction was given to liars and truth tellers as to what strategy they should use in order to

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make a convincing impression. All suspects were given 10 minutes to prepare for the interrogation. The interrogations. The interrogations were conducted using (for practical reasons) four male experimenters who followed pre-defined interrogations scripts. All interrogators were around 30 years of age, and were graduated. Although none of them were professional interrogators, they all had experience in conducting similar interrogations in experimental settings, because they all were involved in conducting our experiments in the past. All interrogators conducted both interrogation types: Early disclosure and Late disclosure. The interrogators were blind to the veracity of the suspects. The interrogations consisted of several steps. For the Early disclosure conditions, the interrogations started with an introduction step, during which the interrogator presented himself, asked the suspect how he or she felt about being interrogated, and presented the suspect with suspicion of guilt concerning a theft. The interrogator then asked the suspect if he or she confessed to the crime, which nobody did. Then, the interrogator told the suspect that there were three pieces of evidence against the suspect. First, one witness had seen the suspect outside the movie store during the day when the wallet was stolen. Second, one witness had seen the suspect in the movie store, close to where the wallet was stolen. Third, the suspect’s fingerprints had been found on the briefcase from which the wallet was stolen. The suspect was told that the fingerprints on the briefcase had been compared to those on a plastic sheet covering the piece of paper on the pre-interrogation instructions which the suspect had read through. The interrogator then asked the suspect to comment on this evidence. Following this, the interrogator asked the suspect to give a free recall about the course of events during the day of the theft, and then posed a number of more specific questions. The specific questions concerned whether and where the suspects had been in the movie store; whether they saw and touched a briefcase, and where they may have touched it. Moreover, the questions concerned whether they had seen someone in or outside the movie store. The reason for the inclusion of these questions was that we wanted all suspect to address the evidence. Finally, the interrogator asked the suspect whether he or she confessed to the crime. Again, nobody did. Then the interrogator ended the interrogation by thanking the suspects for their participation. In the Late disclosure, the same steps were included but in a different order. These interrogations started with the Introduction step, followed by a free recall from the suspect, after which the interrogator posed a number of specific questions (the same as in Early disclosure). The final specific question concerned whether the suspect confessed to the crime, similarly to Early disclosure. After this, the evidence against the suspect was presented, and the suspect was asked to comment on this evidence. Finally, the suspect was thanked for his participation. Post-interrogation questionnaires. The interrogations lasted between 5 and 13 min. After having participated in the interrogations, the suspects were given a post-interrogation questionnaire containing questions about background characteristics (age and sex), ratings of their own truthfulness in their story on a 10-point scale, where 1 indicated totally deceptive and 10 totally truthful, and ratings of motivation on a 10-point scale, where 1 indicated not at all motivated and 10 extremely


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motivated. Finally, they were thoroughly debriefed, thanked and payed for their contribution. Phase 3 Participants. The group of participants acting as observers consisted of 116 undergraduate students (74 females and 42 males, age ranging from 18 to 76 years, M = 27.3 years, SD = 9.40). Procedure. The observers were asked to sit down in a room where a VCR and a TV set were placed. They were then told that they would be shown a video-taped interrogation of a suspect by an interrogator. The interrogation concerned an alleged theft of money that had been stolen from a movie store. The observers were informed that their task was to indicate after the interrogation whether the suspect was lying or telling the truth, that is whether the suspect had stolen the money or not. It was stressed in the instructions that it was as likely that the suspect was lying as it was that he or she was telling the truth. They were also told that some pieces of evidence would be presented during the interrogation by the interrogator. The observers were told that these pieces of evidence were true (i.e., that the interrogator did not make them up), but that they did not exclude the possibility that someone else other than the suspect had committed the crime; it still was a 50% chance that the suspect was innocent. The instruction about the 50% base-rate was included because observers typically have the tendency to assume guilt while watching interrogations (Kassin, Goldstein, & Savitsky, 2003). This tendency could be even stronger in the present experiment due to the strength of the evidence presented during the interrogations. The observers were then shown the interrogation. After this interrogation, they had to answer two questions. First, whether or not the suspect was lying (dichotomous truth/lie judgment), and second, which type of information they used when making the veracity judgment on a 10-point scale, where 1 indicated only nonverbal behavior and 10 only verbal content. All observers saw one interrogation with one suspect, and each interrogation was shown to two observers. Statement–evidence consistency. The interrogations were transcribed and coded in order to examine the degree of consistency with the three pieces of evidence. For the free recall phase, it was coded to what extent the suspect did not mention the three pieces of evidence. Scores could range from 0 to 3 with 3 meaning that the suspect did not mention any of the three pieces of evidence in the free recall phase. For the specific questions phase, it was coded to what extent the statement given by the suspect was inconsistent with the three pieces of evidence. Again, the scores could range from 0 to 3, with 3 meaning that the statement of the suspect was inconsistent with all three pieces of evidence. For example, if the suspect said that he had not touched the briefcase, this means that the statement was inconsistent with the fingerprint evidence.4 4 In

the free recall phase, apart from omissions, it was also scored whether the statement was Consistent, meaning that the statement was consistent with the evidence (e.g., “I touched the briefcase”), Possibly consistent, meaning that the statement could be in line with the evidence and/or did not contradict the evidence (e.g., “I looked around in the box where a briefcase was lying”) and Inconsistent, meaning

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Interrater reliability. One person coded all 58 transcripts, and a random sample of 25% of the material was also coded by a second coder. The interrater agreement for these codings was 96.6%. The discrepancies were resolved in a discussion between the two coders. RESULTS Manipulation Check A t-test was conducted in order to find out whether targets complied with the instructions to lie or tell the truth. Truth tellers (M = 9.76, SD = 0.52) rated their truthfulness as significantly higher than did liars (M = 5.21, SD = 2.07), t(56) = 10.69, p < .001. The video-taped interrogations were checked regarding veracity. It was confirmed that all events described by truth tellers actually occurred, and that all liars distorted the actual course of events. The mean motivation rating was M = 8.10 (SD = 1.52). No participant scored lower than 4 and only four participants scored lower than 6. No difference in motivation emerged between liars and truth tellers, t(56) = 0.77, p = .45, which indicates that both liars and truth tellers were highly motivated.

Veracity Judgments Accuracy in judging veracity. Calculated from the dichotomous truth/lie judgment, the overall accuracy level was 52.6%. Observers in the Early disclosure conditions obtained an accuracy level of 42.8%, while observers in Late disclosure obtained 61.7%. This difference between the groups in accuracy was significant, χ2 (1, N = 116) = 4.11, p < .05, φ = −.19. Hence, Hypothesis 1, stating that observers in the Late disclosure condition would outperform those in Early received support. Separate χ2 -test of the effect of Early and Late disclosure on deception detection accuracy were conducted for truthful and deceptive statements. For truthful statements, it was found that there was no significant difference in accuracy between observers in the Early and Late conditions, χ2 (1, N = 50) = 0.32, p = .57. For deceptive statements, observers in the Late disclosure condition were significantly more accurate than observers in the Early disclosure condition, χ2 (1, N = 66) = 4.86, p < .05, φ = −.27. In Table 1, the accuracy figures broken down for truthful and deceptive statements are presented. Only observers watching deceptive suspects in the Late disclosure condition obtained an accuracy rate significantly above chance (binomial p = .03). that the statement given by the suspect contradicted the evidence (e.g., “I saw a briefcase but I was never even close to it”). In the specific questions phase, apart from inconsistency, it was also scored whether the statement was consistent with the pieces of evidence, possibly consistent with the pieces of evidence, or whether these three pieces of evidence were not mentioned by the suspect. These data were not further analysed.


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Table 1. Observers’ Lie Detection Accuracy in Percentages Actual veracity of statement Disclosing the evidence

Truthful

Deceptive

45.8 53.8

40.6 67.6

Early Late

Statement–Evidence Consistency Table 2 presents the mean scores regarding the consistency and inconsistency variables. Not mentioning the evidence in free recall. In order to examine the effect of the Evidence (early/late) and Veracity (truth/lie) factors on the degree to which the suspects refrained from mentioning the evidence, we conducted a two-way ANOVA with the Not mentioned (in free recall) scale as dependent measure. The analysis revealed significant main effects for the Evidence factor F (1, 54) = 23.21, p < .001, η2 = .30, and veracity factor F (1, 54) = 6.47, p < .05, η2 = .11. There was also a significant interaction F (1, 54) = 10.44, p < .01, η2 = .16. Specific comparisons regarding the veracity factor showed that liars and truth tellers were equally prone to mention the evidence in the Early disclosure condition, t(26) = 0.42, p = .68, and that liars were significantly more prone to not mentioning the evidence compared to truth tellers in the Late disclosure condition, t(28) = −4.93, p < .001. This supports Hypothesis 2. Degree of inconsistency with the evidence in specific questions phase. In order to examine the effect of the Evidence (early/late) and Veracity (truth/lie) factors on the degree to which the suspects gave statements that were inconsistent with the evidence during the specific questions phase, we conducted a two-way ANOVA with the inconsistency in specific questions scale as the dependent measure. There was no significant difference between Early disclosure and Late disclosure in terms of inconsistencies with the evidence, F (1, 54) = 1.16, p = .29. However, compared to truthful statements, deceptive statements were significantly more inconsistent with the evidence, F (1, 54) = 9.12, p < .01, η2 = .14. There was no significant interaction, F (1, 54) = 1.36, p = .25. Specific comparisons regarding the Veracity factor showed that liars and truth tellers were equally inconsistent in the Early disclosure condition, t(26) = 1.31, p = .20, and that liars were significantly more Table 2. Mean Scores for Not Mentioning the Evidence and Inconsistency with the Evidence in the Suspects’ Statements Actual veracity of statement Truthful

Free recall Not mentioning evidence Specific questions Inconsistent

Deceptive

Early

Late

Early

Late

1.25 (0.62)

1.54 (0.66)

1.13 (0.89)

2.59 (0.51)

0.17 (0.39)

0.15 (0.38)

0.44 (0.63)

0.76 (0.66)

Note. Standard deviations are presented in parentheses.

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inconsistent than truth tellers in the Late disclosure condition, t(28) = 2.97, p < .01. This supports Hypothesis 2. Relation between Statement–Evidence Consistency and Veracity Judgments In order to examine the relation between the degree of statement-evidence consistency and the veracity judgments made, we conducted four correlations. First, there was a weak nonsignificant correlation between the accuracy of the observers and the suspects’ (liars and truth tellers combined) tendency to not mention the evidence in the free recall r(116) = −.10, p = .31. Second, there was a significant correlation between the accuracy of the observers and the suspects’ (liars and truth tellers combined) degree of inconsistencies in the specific questions phase, indicating that the more inconsistencies there were in the statement, the more correct the observer was, r(116) = −.20, p < .05. Third, there was a significant correlation between the type of veracity judgment made by the observers and the suspects’ tendency not to mention the evidence in the free recall, indicating that the more the suspect refrained from mentioning the evidence, the more likely the observer was to make a lie judgment, r(116) = −.25, p < .01. Fourth, we found a significant correlation between the type of veracity judgment made and the amount of inconsistencies in the specific questions phase, meaning that the more inconsistencies there were, the more likely the observer was to make a lie judgment, r(116) = −.20, p < .05. Reliance on Verbal and Nonverbal Behavior A two-way ANOVA with evidence and veracity as independent measures and the rating scale of the use of verbal and nonverbal behavior as dependent measure revealed that observers in the Late disclosure condition (M = 6.43, SD = 2.19) reported using verbal behavior to a significantly higher extent than did observers in Early disclosure (M = 5.59, SD = 2.14), F (1, 112) = 4.19, p < .05, η2 = .04. This was in line with Hypothesis 3. There was no difference in ratings between truthful (M = 5.86, SD = 2.35) and deceptive (M = 6.15, SD = 2.09) statements, F (1, 112) = 0.52, p = .48, and the interaction effect was not significant, F (1, 112) = 0.03, p = .88. DISCUSSION Accuracy in Judging Veracity The aim of the study was to explore how strategic disclosure of evidence during an interrogation can affect lie detection accuracy. We first predicted that observers watching an interrogation in which the evidence against the suspect was disclosed in the end of the interrogation would obtain higher accuracy rates than would observers who watched an interrogation in which the evidence was disclosed at the outset of the interrogation. We found support for this prediction in liars; in the Late disclosure they were identified with an accuracy rate of 67.6%. Observers performed poorly in terms of accuracy when the evidence was disclosed in the beginning of the interrogation.

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They identified 45.8% of the truth tellers and 40.6% of the liars in the Early evidence condition. These percentages are in line with previous detection of deception studies (Meissner & Kassin, 2002; Vrij, 2000). This is an important finding with clear relevance for forensic settings. The finding points to the detrimental effect on lie detection accuracy when disclosing the evidence right in the beginning of the interrogation. Although observers in Late disclosure who made judgments of actually deceptive statements were rather accurate (67.6%), they were not accurate to the same extent (53.6%) when making judgments of truth tellers. We propose two complementary explanations for this finding. First, the truth tellers’ stories may fit fairly well with the evidence (at least compared to the deceptive statements in Late disclosure), which makes it difficult for the observers to use verbal content cues when assessing veracity. Hence, they may be confined mainly to nonverbal behavior, which is not a very valuable source of information for lie catchers (DePaulo et al., 2003). Second, it may be that some truth tellers did not provide information about the evidence in the free recall phase, and that their omissions triggered the observers to judge some of the truth tellers as liars. This finding indicates that the technique of disclosing the evidence at the end of the interrogation, as it is operationalized in this study, is mainly a technique for detecting lies rather than truths. It seems that liars encounter more problems than truth tellers do when being interrogated according to the Late disclosure technique. In order to make this understandable, we turn to the analyses of the statement– evidence consistencies.

Statement–Evidence Consistency We predicted that when the evidence was disclosed early in the interrogation, both liars and truth tellers would give statements including this evidence to the same extent. In contrast, we predicted that when the evidence was disclosed late, the liars would be more likely to refrain from providing much information than truth tellers, hence the evidence would be mentioned to a lesser extent by liars than by truth tellers. The results supported this hypothesis. Liars and truth tellers were equally likely to mention the pieces of evidence in their free recall when this evidence was disclosed to them in an early stage. In contrast, liars were more likely to not mention information about the pieces of evidence in their free recall when this evidence was presented to them at a late stage. We further predicted that in the specific questions phase, liars’ statements would be more inconsistent with the evidence than truth tellers’ statements, in particular when this evidence was dislosed late. The results supported this, as liars and truth tellers were equally inconsistent when the evidence was disclosed early, whereas liars were more inconsistent than truth tellers when the evidence was disclosed late. Importantly, we found that the degree of statement–evidence consistency was related to the type of veracity judgment that the observers made, in that more statement–evidence inconsistency led the observers to make lie judgments. This

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indicates that the observers were able to focus their attention to this cue to deception. Suspects’ Strategies during Early Disclosure Taken together, these findings indicate that when the evidence against the suspect is released at the outset of the interrogation, liars and truth tellers behave similarly in that they incorporate information about the evidence in their free recall statement, and they do not contradict these pieces evidence when asked specific questions about them. These similarities between liars and truth tellers are reflected in observers’ abilities to make accurate veracity judgments; when watching these interrogations, observers have difficulties distinguishing between truthful and deceptive statements. Suspects’ Strategies during Late Disclosure It seems that liars, who are asked to provide a free recall when lacking knowledge about the evidence against them, avoid providing details about this evidence to a larger extent than do truth tellers. This tendency may reflect a strategy to avoid being put in connection with the crime, that is to avoid to give details that may seem self-incriminating. For example, concerning our study, liars may think that if they admit that they touched the briefcase from which the wallet was stolen, they will have a difficult time explaining why they touched it. In order to explain this, they must fabricate a plausible reason. This fits well with the notion of the illusion of transparency (Gilovich et al., 1998; Kassin & Norwick, 2004), according to which liars will be reluctant to tell outright lies out of fear for their detectability. Therefore, the safest way out according to them may be to not mention the briefcase at all. Indeed, if the interrogator himself does not mention the fingerprints on the briefcase when he asks the suspect to provide a free recall (which is the case in Late disclosure in this study), this may indicate that he is not aware of their existence. However, when the liars subsequently are asked to answer follow-up questions, they are forced into contradicting the evidence. For example, if a liar is asked the question whether he saw a briefcase, he may deny this order not to be inconsistent with his free recall statement in which he never mentioned a briefcase. The consequence of this may be that the liar is consistent to some degree with his former statement, but inconsistent with the evidence. However, since the liar in Late disclosure is unaware or unsure of the evidence against him during the free recall, he will not know he is contradicting these pieces of evidence. In some sense the Late disclosure technique causes the strategies of liars to backfire, since their reluctance to give details about the evidence in the free recall phase can be used as a cue to deception. Moreover, the outright inconsistencies that tend to results from the specific question phase may contribute to the decrease in the suspect’s credibility. Compared to liars, truth tellers withheld details concerning the evidence during free recall to a lesser extent, and contradicted them to a lesser extent in the specific question phase. This may be explained by the fact that in terms of the evidence against the suspects in the present study, truth tellers had a legitimate reason for being in the video store and touching the briefcase, since they were looking for a

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specific item in the store. When being interrogated, they did not need to fabricate a reason in order to provide explanations for the evidence. The self-presentational perspective (DePaulo et al., 2003) states that even truth tellers tend to edit their self-presentations in order to appear credible. However, it is not surprising that the information concerning the evidence was not withheld by truth tellers to the same extent as by liars. These truth tellers probably did not consider this information damaging for their credibility, since they could provide a legitimate reason for the existence of this evidence. In line with our results, a recent study showed that innocent mock suspects were more prone to waive their Miranda rights to silence than were guilty ones (Kassin & Norwick, 2004). By waiving these rights, the suspects agreed to submit to an interrogation about the mock crime of which they were accused. Interestingly, a majority of the innocent waivers offered explanations for this indicating a belief in the power of truth to prevail, such as “I did nothing wrong” and “I didn’t have anything to hide.” Kassin and Norwick concluded that this tendency indicates that people have a na¨ıve faith in the power of their own innocence to set them free. It seems as if the innocent suspects in the present study to some extent felt similarly and acted in line with this faith. Observers’ Strategies As discussed earlier, observers in Late disclosure were better than those in Early disclosure in terms of lie detection accuracy. We attributed the higher accuracy in Late disclosure to the observed lack of consistency between the statement of the lying suspect and the evidence. This lack of consistency was possible to divide into two components: First, lying suspects in Late disclosure were prone to avoid mentioning the evidence in their free recall statement. Second, these lying suspects had a tendency to contradict the evidence in the subsequent specific question phase. We found that observers in Late disclosure reported relying more on the verbal content when detecting deceit than did observers in Early disclosure. This can be taken as support for the idea that the differences in lack of statement–evidence consistency between Early and Late disclosure accounted for the differences in lie detection accuracy. It thus seems as if the Late disclosure technique to some extent managed to draw the observers’ attention to particular aspects of the suspects’ verbal behavior, such as lack of consistency. Judging from the accuracy rate obtained by observers in Late disclosure, these verbal behaviors were relatively valid cues to deception. These findings are in line with other studies, where it was also found that observers direct their attention to lack of consistency when attempting to detect de¨ ceit (Granhag, Stromwall, and Hartwig, 2004; Park, Levine, McCornack, Morrison, & Ferrara, 2002). One benefit of making observers attend to verbal content cues such as statement–evidence consistency is that such cues may be of value in court proceedings. If the prosecution manages to demonstrate that the defendant in an interrogation (where the evidence was withheld from the suspect and not disclosed until the end of the interrogation) has had a chance to come up with a plausible explanation for the findings pointing to his guilt, but that the defendant has contradicted these

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findings, his credibility may be questioned. In contrast, suspicious nonverbal behavior during a police interrogation is in itself of little or no value for factfinders in court. Future Directions This study is but a first step in exploring the potentials of strategic disclosure of evidence as a lie detection tool, and the technique could be refined to include several steps. For example, it might be worthwhile to investigate how more sophisticated ways of disclosing evidence such as different drip-feeding procedures in which parts of the evidence are disclosed throughout the interrogation, may moderate deception detection performance (Granhag & Vrij, 2005; Vrij, 2004). Moreover, future research may investigate how strategic disclosure of evidence affects guilty and innocent suspects to make admissions. It could also be valuable to examine how the positive effects of strategic disclosure of evidence are affected by the amount of information held by the suspects. How does the technique affect lie detection accuracy if the suspect is aware of a great deal of the evidence against him or her, or if he or she suspects the existence of specific evidence? We found that the technique of disclosing the evidence at the end of the interrogations proved to be mainly a technique for pinpointing liars; truth tellers were not identified with the same accuracy. Misclassification of truth tellers is a more serious problem than misclassification of liars, due to the risk of wrongful convictions (Scheck, Neufeld, & Dwyer, 2000). Future research could attempt to increase accuracy in detecting truth tellers, perhaps by informing lie-catchers about the likely strategy used by truth tellers. It seems as if truth tellers prefer to not hold information about the course of events back, and to provide much information about what has happened. If lie-catchers are aware of this, they may become more accurate in pinpointing truth tellers. ACKNOWLEDGMENTS Many thanks are due to Detective Superintendent Royne Nilsson for inspiring us to conduct this study. Thanks are also due to Simon Andersson, Karl Ask, Karl ¨ Malin Olsson, Viktor Prytz and Anna Rebelius for help Gillholm, Sara Landstrom, with the collection and coding of data. This research was funded by a grant from the Swedish Research Council given to the second author. REFERENCES DePaulo, B. M., Lindsay, J. J., Malone, B. E., Muhlenbruck, L., Charlton, K., & Cooper, H. (2003). Cues to deception. Psychological Bulletin, 129, 74–118. Gilovich, T., Savitsky, K., & Medvec, V. H. (1998). The illusion of transparency: Biased assessments of others’ ability to read one’s emotional states. Journal of Personality and Social Psychology, 75, 332–346.

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