Research in Developmental Disabilities 36 (2015) 191–197
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Research in Developmental Disabilities
(The null) Importance of police experience on intuitive credibility of people with intellectual disabilities Antonio L. Manzanero a,*, Jose´ M. Quintana b, Marı´a J. Contreras c a
Universidad Complutense de Madrid, Spain Guardia Civil, Spain c Universidad Nacional de Educacio´n a Distancia, Spain b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 10 July 2014 Received in revised form 1 October 2014 Accepted 2 October 2014 Available online
In the present study, the intuitive ability of police to discriminate between real and false statements of people with mild and moderate (IQ range = 50–80, average = 60.0) intellectual disabilities (ID) was analyzed. The assessments issued by groups with different levels of experience in police techniques (psychology students, and police officers) were compared. The results showed no differences between the two groups in their ability to discriminate (d0 = 0.785 and d0 = 0.644, respectively). When the experience of the police was taken into consideration, no differences were found between ‘‘experienced’’ and ‘‘novice’’ police officers (d0 = 0.721 and d0 = 0.582, respectively). No differences were found in response criteria, which were neutral in all cases. Moreover, 34.73% of cases evaluated by the inexperienced group were incorrectly discriminated, in comparison to the 37.75% of incorrect assessments made by police. The implications of the limited ability of intuition to discriminate between real and simulated victims with ID, which did not yield significant differences between experienced and inexperienced assessors in obtaining and assessing statements, are discussed. In light of the results of this study, it is concluded that adequate resources and standardized procedures to properly address people with ID who come into contact with the police and judicial institutions need to be provided. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Credibility Eyewitness testimony Learning disability Deception
1. Introduction According to data from the Spanish Judicial Police, between 2008 and 2010, there were 10,045 allegations in Spain in which a person with intellectual disability (ID) was involved, either as victim, perpetrator or witness (Gonza´lez, Cendra, & Manzanero, 2013). The vulnerability of people with ID makes them a population at risk, increasing the likelihood of becoming crime victims themselves. The main causes of vulnerability are: ignorance of what constitutes an offence, difficulties in communication (Brownlie, Jabbar, Beitchman, Vida, & Atkinson, 2007; Oosterhoorn & Kendrick, 2001), greater dependency of relationships with caregivers, which makes claiming more difficult (Sobsey, 2002; Westcott & Jones, 1999), and their need for social approval.
* Corresponding author. E-mail address: [email protected] (A.L. Manzanero). http://dx.doi.org/10.1016/j.ridd.2014.10.009 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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Probably, one of the main obstacles in crime investigation originates in the stereotypes that society holds on the testifying ability of people with intellectual disabilities. Existing stereotypes (Henry, Ridley, Perry, & Crane, 2011; Peled, Iarocci, & Connolly, 2004; Sobsey & Doe, 1991; Stobbs & Kebbell, 2003; Tharinger, Horton, & Millea, 1990; Valenti-Hein & Schwartz, 1993) about these people tend to make them less credible than other victims, which could lead to the rejection of proceedings in which the victim has an intellectual disability. Henry et al. (2011) evaluated the credibility of children with ID and of developmentally normal children and found that the former, because they gave fewer details, were less credible than the latter. Peled et al. (2004) explored the perceived credibility of young persons with ID who were required to give testimony in a legal setting. Half of the observers were told beforehand that the witness had moderate intellectual disability, and the other half were told that the witness was a person who was developmentally normal. When subsequently questioned about the credibility of the testimonies, they stated that those testimonies given by a person with ID were considered less credible. On the other hand, it has been proposed that lying is cognitively more complex than telling the truth (Vrij, Fisher, Mann, & Leal, 2006). Therefore, lying would imply a greater demand of cognitive resources (Vrij & Heaven, 1999). In this sense, some of the existing stereotypes on the ability of people with intellectual disabilities have lead to the belief that they are not capable of producing complex lies, therefore making them more credible (Bottoms, Nysse-Carris, Harris, & Tyda, 2003). The two stereotypes are contradictory, but both are likely to influence the ability to distinguish truth and falsehood in people with intellectual disabilities. In a previous study (Manzanero, Alemany, Recio, Vallet, & Aro´ztegui, 2015), the differentiating characteristics of true and false accounts made by people with intellectual disabilities were analyzed using procedures based on Reality Monitoring (Manzanero & Diges, 1995; Sporer, 1997), and intuitive ability to discriminate between the two types of stories. The results showed that accounts differed according to their origin in the amount of detail, the incardination of the facts in a spatial and temporal context, and the reproduction of conversations. It was also noted that, from an intuitive point of view, people with little knowledge about developmental disorders and no experience in interacting with people with intellectual disabilities were able to discriminate the two types of statements above chance, but with a high probability of error (0.381). In general, it could be argued that the ability to assess the credibility of a statement is relatively low and tends to be close to random. Most studies (Aamodt & Custer, 2006; Akehurst, Bull, Vrij, & Ko¨hnken, 2004; Bond, 2007; Bond & DePaulo, 2006; Mann & Vrij, 2006; Mann, Vrij, & Bull, 2004; Manzanero & Diges, 1994) show success rates in discriminating between real and false accounts close to 50% with a tolerance of approximately 10%. The percentage of hits would be similar for different groups, depending on their experience (police, judges, students, etc.). The only difference usually found (Bond & DePaulo, 2006; Meissner & Kassin, 2002; Vrij, 2000) is that subjects without training in the analysis of credibility, in general, tend to believe the statements independently from their reality, whereas judges and police are more likely to exhibit mendacity, i.e. they tend to think that accounts are false. However, some previous studies (Ekman & O’Sullivan, 1991; Ekman, O’Sullivan, & Frank, 1999; Ericsson & Smith, 1991) had pointed out that experts in these tasks (such as forensic psychologists, lawyers or the police) would have greater ability to discriminate false testimony from other true statements than subjects with no experience. However, most studies refer to non-significant differences in the ability to detect deception when comparing expert and lay assessors (Bond & DePaulo, 2006; DePaulo & Pfeifer, 1986; Garrido, Masip, & Herrero, 2004; Goodman, Batterman-Faunce, Schaaf, & Kenney, 2002; Kraut & Poe, 1980). Vrij (2004) suggests ten possible causes for the low accuracy in detecting deception: (a) no absolute indicators of lies; (b) subtle differences in lying vs. telling the truth; (c) heuristic decision making; (d) adherence to rules of conversation that hinder detection; (e) reliance on non-diagnostic evidence; (f) attention to channels is not very revealing; (g) dismissal of inter-individual differences in respondents (idiosyncratic error); (h) rejection of the influence of situational factors (intra-individual differences); (i) dismissal of the inter-individual differences of the detectors; and (j) inadequate use of interviewing and interrogation techniques. In addition, limited ability to discriminate may be because actual and false accounts are not sufficiently different (Bekerian & Dennett, 1992; Manzanero, 2006, 2009; Porter & Yuille, 1996; Sporer & Sharman, 2006; Vrij, 2005; Vrij, Akehurst, Soukara, & Bull, 2004), and differential features may appear depending on variables such as retention interval, preparation of narrative (Manzanero & Diges, 1995) or the degree of involvement in the event (Manzanero, El-Astal, & Aro´ztegui, 2009). The aim of this study was to analyze the ability of two groups with different degrees of experience in obtaining and assessing statements (students vs. Judicial Police) to discriminate between actual and simulated victims with ID. According to the ‘‘mendacity’’ bias described above, agents would exhibit a greater tendency to disbelieve the statement provided. Furthermore, this study aims to investigate whether experience influences the assessment of the credibility of a witness. The hypothesis is that the greater the experience, the more accurate judgments about credibility will be. 2. Method 2.1. Participants Two groups of assessors with different experience in obtaining and assessing statements participated in the experiment. The inexperienced group was composed of 53 undergraduate Psychology students (16 men and 37 women) from Universidad Complutense and Universidad de Comillas (Madrid), who had no specific experience or knowledge on how to
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obtain and assess statements (all of them could have participated in civil jury). The average age was 30.32 years (SD = 10.02). They completed a total of 1189 assessments (569 true statements and 620 false statements). The experienced group was composed of 28 police officers who work in special units of the Judicial Police (23 men and 5 women), in charge of investigating crimes against persons. Their main functions/tasks include interviewing and interrogating those involved in these crimes, and therefore have experience in detection (or at least in theory) of lies or inconsistencies in these statements and in performing judgments/assessments about credibility. The average age was 38.5 years (SD = 6.10, interval between 29 and 52) and the average experience in Judicial Police was 10.93 years (SD = 7.98, interval between 2 and 30). To check the degree of experience in the group of policemen was important, subsequently this group was divided into two subgroups. One group was composed of ‘‘veteran’’ police, consisting of 13 officers (12 men and 1 woman) with over 10 years experience in Judicial Police Units (with an average of 18.15 years of experience, SD = 5.03). They performed a total of 361 assessments (167 assessments of true stories and 194 assessments of false stories). The second group consisted of 15 ‘‘novice’’ officers (11 men and 4 women), with less seniority and less than 10 years of service in these specialized units (average of 4 years, SD = 1.88). They performed a total of 402 assessments (184 assessments of true stories and 218 assessments of false stories). Because police officers do not receive specific training to act with people with ID, students who participated in the study had no specific knowledge about intellectual disabilities. 2.2. Procedure As in many cases involving persons with ID, where judicial statements are collected some years later, a real event that took place 2 years ago was chosen for conducting this research – a group of persons with intellectual disability from the Fundacio´n Carmen Pardo-Valcarce went on a day trip, during which the bus they were travelling in caught fire. A researcher selected the people with ID who had given statements using a truthfulness criteria: ‘‘real victims’’ for those who went on the day trip or ‘‘simulated victims’’ for those who did not go on the day trip but knew about the event from references made to it. The two groups were of comparable IQ (see Table 1). All persons with ID who participated in the study (or their legal guardian) signed consent for voluntary participation. All persons with ID were informed of the purpose of the research and were given instructions. Simulated victims who did not go on the day trip were given a summary of the most important information about the day trip, such as its location, the main complication on the day trip, and the course of the day. To increase the ecological validity of our study, all people in the two groups were encouraged to give their testimonies as best they could. While they were not put under the stress of making the interviewer believe their testimony (to prevent undue tension in the interview), we decided to invite them to a soda if they succeeded in convincing the interviewer that they had, in fact, experienced the event. As can be observed in Table 1, each condition consisted of more than 10 stories, as is suggested in previous research, because if the number of reports is small, the possibility of obtaining results by chance increases significantly. Frank and Feeley (2003) advise, in line with other detection of deception researchers, that the number of statements to be assessed in a detection test should be close to 10. Two investigators, ‘‘blind’’ to the real or simulated victim condition, experts in interviewing and obtaining victim testimonies, conducted interviews individually with each ‘‘victim’’. All interviews were audio-visually recorded. Interviews were always conducted following the same instructions: ‘‘We would like you to tell us everything that happened, from beginning to end, with as many details as possible, when you went on that day trip where the bus burned down. We want you to tell us everything, even the things that seem unimportant’’. Once the free account of the incident was obtained from all participants, they were asked the same questions: Who were you with?, Where did it happen?, Where were you going?, What did you do? and What happened afterwards? The order of the interviews was randomized. Each victim was interviewed only once, since if they were to be interviewed more than once, there would be the risk of not judging them on the veracity of the statement, but rather on the consistency of their behaviour shown in each different session. The statements had a mean duration of 5 min and 15 s (SD = 2.3027), with the shortest interview lasting 2½ min and the longest 12 min and 26 s. Their duration is considered sufficient to issue credibility judgments, since very short statements (under 2 min) may lack, especially in subjects with intellectual disability, enough items on which to base a judgement. Once obtained, the statement videos were edited so that none of them gave any explicit indication as to which group the victims
Table 1 Frequencies of true and false statements and characteristics of the two ‘‘victims’’ groups. True statements N = 13
Mean IQ: 60.72 (SD = 9.67) Range IQ: 50–78 Mean age: 35.18 (SD = 7.16)
False statements N = 16
Mean IQ: 59.30 (SD = 9.44) Range IQ: 48–80 Mean age: 33.75 (SD = 6.78)
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Table 2 Frequencies and percentage of hits (H), correct rejections (CR), false alarms (FA) and omissions (O) obtained by each group. Evaluation
Origin of the statement Simulated
Real
Inexperienced (students)
Lie Truth
CR: 404 (65.16%) FA: 216 (34.84%) 620 (100%)
O: 197 (34.62%) H: 372 (65.37%) 569 (100%)
Experienced (police)
Lie Truth
CR: 268 (58.64%) FA: 189 (41.35%) 457 (100%)
O: 130 (33.50%) H: 258 (66.49%) 388 (100%)
belonged to (for example, ‘‘actually, what I’m telling you is not true. I know I do not have to lie’’). Three interviews in the ‘‘false’’ group were discarded because the victims were not able to follow the instructions. The videos of the true and false victims were shown on a large-format screen. All assessors attended the screening at the same time, but they were prevented from interacting among themselves in order not to bias each other while making their individual assessments. The videos were shown in random order to prevent a learning effect from differentially impacting their ability to evaluate true and false statements. After each video was shown, the assessors were asked to categorize the victim as true or false. The general instructions given were as follows: ‘‘Next, a series of videos will be shown in which people with intellectual disability are giving a statement about a bus accident. Some of the statements were given by individuals who had actually experienced that event; the others were given by individuals who, although they had not experienced the event directly, had been told about the event, and have given their statement with the intention of making us believe they had experienced the accident. Your task is to decide who is an actual victim and who is a simulated victim. As you are assessing each victim, bear in mind that the interviewees are all persons with intellectual disability, so their way of telling things may be peculiar/different.’’1 In order to measure the accuracy with which each of the two groups of assessors evaluating the credibility of the victims, measures of accuracy (hit, false alarm, correct rejection and omission), the discriminability index d0 , c response criteria from Signal Detection Theory (Tanner & Swets, 1954) and the overall percentage of hits and mistakes, were used. 3. Results 3.1. Intuitive assessment of credibility The analysis of the credibility assessments made from intuition shows that the inexperienced group is able to discriminate between real and false statements above chance, as the discriminability index d0 was 0.785 (SD = 0.075), Zd = 10.492; p < 0.05. Whereas the response criterion c yielded a score of 0.003 (SD = 0.037), Zc = 0.078; p = n.s., which would indicate it would not be different from a neutral criterion. The percentage of correct classifications was 65.26%. The analysis of the credibility assessments made from intuition shows that the Judicial Police officers are able to discriminate between real and false statements also above chance, as the discriminability index d0 was 0.644 (SD = 0.088), Zd = 7.285; p < 0.05. Whereas the response criterion c yielded a score of 0.104 (SD = 0.044) Zc = 2.347; p = n.s., indicating a neutral criterion. The percentage of hits was 62.24%. Table 2 shows the frequency and percentage of hits (H), correct rejections (CR), false alarm (FA) and omissions (O) obtained by each group. The results show that the performance of the officers of the Judicial Police of the Guardia Civil is not statistically different from that obtained by the control group. There were no significant differences in effectiveness in discriminating between true and false statements between police and students (Z = 1.219, p = n.s., Cohen’s d = 1.724, r = .653). Fig. 1 shows the ROC curves (Swets, 1986) on the discrimination ability of Judicial Police and students. On the other hand, the hypothesis regarding officers tending not to believe the statement provided (mendacity bias reflected in other research with police) is not confirmed, and the criterion (c) scores obtained show that both, the experienced and the inexperienced group, present a neutral response criterion. 3.2. Distinction amongst officers of the Judicial Police in light of experience In order to check if the years of experience influence the results, the analysis of the intuitive assessments of the two subgroups within the group of experts is presented below. Table 3 shows the results of accuracy obtained in the credibility judgments by the group of ‘‘veteran’’ and ‘‘novice’’ officers.
1 In and of itself, the obvious disability of persons with ID could be one of the indicators on which the students based their intuitive assessments. Correlations were made between the statements the students intuitively evaluated as true and the IQ of the persons with ID who gave those statements, and the results showed a null correlation (r(23) = 0.006, p = n.s.).
[(Fig._1)TD$IG]
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Fig. 1. ROC curves of the discrimination ability of police officers (left) and students (right).
The analysis of the credibility assessments made from intuition shows that ‘‘veterans’’ are able to discriminate between real and false statements above chance, as the discriminability index d0 was 0.721 (SD = 0.136), Zd = 5.323; p < 0.05. While the response criterion c reached a neutral criterion, with a score of 0.032 (SD = 0.068) Zc = 0.470; p = n.s. The percentage of hits was 63.98%. The analysis of the credibility assessments made from intuition also shows that the ‘‘novice’’ officers with less than 10 years of experience in Judicial Police, are able to discriminate between real and false statements above chance, as the index discriminability d0 was 0.582 (SD = 0.128), Zd = 4.562; p < 0.05. While the response criterion c reached a score of 0.071 (SD = 0.064) Zc = 1.110; p = n.s., indicating a neutral criterion. The percentage of correct classifications was 61.19%. The difference between ‘‘expert’’ and ‘‘novice’’ officers indicates that agents that have greater seniority in the JP specialty do not show greater accuracy as the discriminability does not differ significantly (Z = 0.744, p = n.s., Cohen’s d = 1.052, r = .466). 4. Discussion From the data obtained in the present study, it is clear that no significant differences were found in terms of experience to discriminate between groups while assessing true and false statements issued by people with intellectual disabilities. These data show that the ability to discriminate between these two groups based on their experience and knowledge to obtain and assess statements produced over 60% of hits of the statements, though this percentage is close to random. Therefore, the present study supports previous studies that highlight the absence of differences between experienced and inexperienced assessors in discriminating between true and false statements issued by people without ID (Bond & DePaulo, 2006, 2008; DePaulo & Pfeifer, 1986; DePaulo, Stone, & Lassiter, 1985; DePaulo, Zuckerman, & Rosenthal, 1980; Goodman et al., 2002; Kraut, 1980; Kraut & Poe, 1980; Vrij, 2000; Vrij & Graham, 1997). And in turn, our results do not support the studies that have shown that police experience improves performance in lie detection (Ekman & O’Sullivan, 1991; Ekman et al., 1999). Hence, we must conclude that experience is not sufficient to discriminate between real and simulated victims with ID and when the event took place a long time ago, and that specific techniques that help perform this task with a lower error rate should be enhanced. These techniques should focus mainly on decreasing the false alarm rate, which is around 40% of the classifications of false statements. This is necessary to reduce the consequences for law enforcement resulting from the results of this research, if they were to be extrapolated to cases of real/actual research that could lead to the arrest of an innocent person. Previous studies may shed some clues on the cognitive basis that explain this excessive false alarm rate in the assessment of statement made by people with ID. Manzanero et al. (2015) showed how people with ID narrated an experience they had not lived in a way that assessors tended to categorize these stories as true. Furthermore, sometimes trying to remember Table 3 Accuracy obtained in credibility assessments issued by ‘‘veteran’’ and ‘‘novice’’ officers. Evaluation
Origin of the statement Simulated
Real
Veteran police
Lie Truth
CR: 122 (62.89%) FA: 72 (37.11%) 194 (100%)
O: 58 (34.73%) H: 109 (65.27%) 167 (100%)
Novice police
Lie Truth
CR: 128 (58.72%) FA: 90 (41.28%) 218 (100%)
O: 66 (35.87%) H: 118 (64.13%) 184 (100%)
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information from an episode (e.g. an event occurred in distant time) may require more cognitive effort than inventing it, as a false statement may very well correspond to a prototype scene or mindset that occurs following a script and that does not require a cognitive effort or at least less effort than a genuine memory. Therefore, an essential process in the formation of police technicians who must work on testimonies of people with ID in relation to reducing false alarms is to alert them that disability does not inoculate against the production of false testimony: people with ID may have an ability to develop false statements that do not differ from how people without ID tell them. As for the results obtained regarding the absence of significant differences in the performance of experienced and novice police officers, this work highlights the need to study how the variable ‘‘experience’’ is operationalized, and whether the training received and the specific functions perform may be influencing and compensating for the lack of years of service with different skills. Usually, and also in this study, experience is measured only in number of years served and does not take into account other indicators related to the quality and intensity of work during those years. 5. Conclusions From the present study, the reflection on the procedure followed within the police and judicial field in cases in which the credibility of the testimony of a person with intellectual disabilities must be assessed seems necessary. In light of the obtained results, it is clear that intuition is not a good way to assess the testimony credibility of these victims, in the case of civil juries inexperienced in obtaining and evaluating statements, but not even in cases where the professional has experience in evaluating testimonies as part of their daily work. The lack of success in discriminating between real and fake statements by intuition could be solved with the use of specific techniques for analyzing credibility. The main problem that we face in the field of analysis of testimonies of people ˜ oz, Sotoca, & Manzanero, with ID is that, so far, such techniques have not been adapted to people with ID (Gonza´lez, Mun 2013), such as the use of the Criteria-Based Content Analysis (CBCA) in the case of children with normal development (i.e. Stro¨mwall, Bengtsson, Leander, & Granhag, 2004). This system of credibility assessment based on memory processes is the most established and researched. It has two criteria known as ‘‘unstructured production’’ (spontaneous reproduction) and ‘‘amount of details’’ (or sufficient details), which seem responsible for distinguishing between honest and false statements. This is because the memories of external events are more detailed and have a looser, more spontaneous structure than memories derived from imagination or fantasy. However, the data obtained in this research show that they are far from being effective, so it is necessary to devote all efforts in developing specific tools tailored to victims with ID. Not to mention that, as highlighted in this paper, people with ID probably issue statements from which it is not possible to obtain such a spontaneous and detailed account as is desirable due to their cognitive and communication difficulties. Among the usual difficulties in analyzing testimonies of people with ID within a police environment are those characteristic to the victim that interfere with his/her statement: low self-esteem, poor social skills, dependence, acquiescence, ‘‘submission’’, etc. That is, a number of factors that make these individuals very vulnerable and prone to suffer abuse (Joyce, 2003). In this sense, participants in this study had no specific knowledge about intellectual disabilities. Note that police officers do not receive specific training to act with people with ID. Future studies could consider the importance of this knowledge in the development of credibility judgments. Therefore, until research does not demonstrate the effectiveness/reliability of other credibility indicators, the testimony of these victims should be taken as just another indication and should be contrasted with other sources of information available to the researcher. 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International developments in research and practice (pp. 56–63). Berlin: W. De Gruyter & Co. Manzanero, A. L., El-Astal, S., & Aro´ztegui, J. (2009). Implication degree and delay on recall of events: An experimental and HDV study. The European Journal of Psychology Applied to Legal Context, 1(2), 101–116. Meissner, C. A., & Kassin, S. M. (2002). ‘‘He’s guilty!’’: Investigator bias in judgments of truth and deception Law and Human Behaviour, 26, 469–480. Oosterhoorn, R., & Kendrick, A. (2001). No sign of harm: Issues for disabled children communicating about abuse. Child Abuse Review, 10(4), 243–253. Peled, M., Iarocci, G., & Connolly, D. A. (2004). Eyewitness testimony and perceived credibility of youth with mild intellectual disability. Journal of Intellectual Disability Research, 18(7), 669–703. Porter, S., & Yuille, J. C. (1996). The language of deceit: An investigation of the verbal cues to deception in the interrogation context. Law and Human Behavior, 20, 443–458. Sobsey, D. (2002). Exceptionality, education, and maltreatment. Exceptionality, 10, 29–46. Sobsey, D., & Doe, T. (1991). Patterns of sexual abuse and assault. Sexuality and Disability, 9(3), 243–259. Sporer, S. L. (1997). The less travelled road to truth: Verbal cues in deception detection in accounts of fabricated and self-experienced events. Applied Cognitive Psychology, 11(5), 373–397. Sporer, S. L., & Sharman, S. J. (2006). Should I believe this? Reality monitoring of accounts of self-experienced and invented recent and distant autobiographical events. Applied Cognitive Psychology, 20, 837–854. Stobbs, G., & Kebbell, M. (2003). Juror’s perception of witnesses with intellectual disabilities and influence of expert evidence. Journal of Applied Research in Intellectual Disabilities, 16, 107–114. Stro¨mwall, L. A., Bengtsson, L., Leander, L., & Granhag, P. A. (2004). Assessing children’s statements: The impact of a repeated experience on CBCA and RM ratings. Applied Cognitive Psychology, 18, 653–668. Swets, J. A. (1986). Indices of discrimination or diagnostic accuracy: Their ROCs and implied models. Psychological Bulletin, 99(1), 100–117. Tanner, W. P., Jr., & Swets, J. A. (1954). A decision-making theory of visual detection. Psychological Review, 61(6), 401–409. Tharinger, D., Horton, C., & Millea, S. (1990). Sexual abuse and exploitation of children and adults with mental retardation and other handicaps. Child Abuse and Neglect, 14, 301–312. Valenti-Hein, D. C., & Schwartz, L. D. (1993). Witness competency in people with mental retardation: Implications for prosecution of sexual abuse. Sexuality and Disability, 11, 287–294. Vrij, A. (2000). Detecting lies and deceit. The psychology of lying and the implications for professional practice. Chichester: John Wiley and Sons. Vrij, A. (2004). Why professionals fail to catch liars and how they can improve. Legal and Criminological Psychology, 9(2), 159–181. Vrij, A. (2005). Criteria-based content analysis: A qualitative review of the first 37 studies. Psychology, Public Policy, and Law, 11(1), 3–41. Vrij, A., Akehurst, L., Soukara, S., & Bull, R. (2004). Let me inform you how to tell a convincing story: CBCA and reality monitoring scores as a function of age, coaching, and deception. Canadian Journal of Behavioural Science, 36(2), 113–126. Vrij, A., & Graham, S. (1997). Individual differences between liars and the ability to detect lies. Expert Evidence, 5, 144–148. Vrij, A., & Heaven, S. (1999). Vocal and verbal indicators of deception as a function of lie complexity. Psychology, Crime, & Law, 5, 203–215. Vrij, A., Fisher, R., Mann, S., & Leal, S. (2006). Detecting deception by manipulating cognitive load. Trends in Cognitive Sciences, 10, 141–142. Westcott, H., & Jones, P. (1999). Annotation: The abuse of disabled children. Journal of Child Psychology & Psychiatry, 40, 497–506.
Contents lists available at ScienceDirect
Research in Developmental Disabilities
(The null) Importance of police experience on intuitive credibility of people with intellectual disabilities Antonio L. Manzanero a,*, Jose´ M. Quintana b, Marı´a J. Contreras c a
Universidad Complutense de Madrid, Spain Guardia Civil, Spain c Universidad Nacional de Educacio´n a Distancia, Spain b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 10 July 2014 Received in revised form 1 October 2014 Accepted 2 October 2014 Available online
In the present study, the intuitive ability of police to discriminate between real and false statements of people with mild and moderate (IQ range = 50–80, average = 60.0) intellectual disabilities (ID) was analyzed. The assessments issued by groups with different levels of experience in police techniques (psychology students, and police officers) were compared. The results showed no differences between the two groups in their ability to discriminate (d0 = 0.785 and d0 = 0.644, respectively). When the experience of the police was taken into consideration, no differences were found between ‘‘experienced’’ and ‘‘novice’’ police officers (d0 = 0.721 and d0 = 0.582, respectively). No differences were found in response criteria, which were neutral in all cases. Moreover, 34.73% of cases evaluated by the inexperienced group were incorrectly discriminated, in comparison to the 37.75% of incorrect assessments made by police. The implications of the limited ability of intuition to discriminate between real and simulated victims with ID, which did not yield significant differences between experienced and inexperienced assessors in obtaining and assessing statements, are discussed. In light of the results of this study, it is concluded that adequate resources and standardized procedures to properly address people with ID who come into contact with the police and judicial institutions need to be provided. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Credibility Eyewitness testimony Learning disability Deception
1. Introduction According to data from the Spanish Judicial Police, between 2008 and 2010, there were 10,045 allegations in Spain in which a person with intellectual disability (ID) was involved, either as victim, perpetrator or witness (Gonza´lez, Cendra, & Manzanero, 2013). The vulnerability of people with ID makes them a population at risk, increasing the likelihood of becoming crime victims themselves. The main causes of vulnerability are: ignorance of what constitutes an offence, difficulties in communication (Brownlie, Jabbar, Beitchman, Vida, & Atkinson, 2007; Oosterhoorn & Kendrick, 2001), greater dependency of relationships with caregivers, which makes claiming more difficult (Sobsey, 2002; Westcott & Jones, 1999), and their need for social approval.
* Corresponding author. E-mail address: [email protected] (A.L. Manzanero). http://dx.doi.org/10.1016/j.ridd.2014.10.009 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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Probably, one of the main obstacles in crime investigation originates in the stereotypes that society holds on the testifying ability of people with intellectual disabilities. Existing stereotypes (Henry, Ridley, Perry, & Crane, 2011; Peled, Iarocci, & Connolly, 2004; Sobsey & Doe, 1991; Stobbs & Kebbell, 2003; Tharinger, Horton, & Millea, 1990; Valenti-Hein & Schwartz, 1993) about these people tend to make them less credible than other victims, which could lead to the rejection of proceedings in which the victim has an intellectual disability. Henry et al. (2011) evaluated the credibility of children with ID and of developmentally normal children and found that the former, because they gave fewer details, were less credible than the latter. Peled et al. (2004) explored the perceived credibility of young persons with ID who were required to give testimony in a legal setting. Half of the observers were told beforehand that the witness had moderate intellectual disability, and the other half were told that the witness was a person who was developmentally normal. When subsequently questioned about the credibility of the testimonies, they stated that those testimonies given by a person with ID were considered less credible. On the other hand, it has been proposed that lying is cognitively more complex than telling the truth (Vrij, Fisher, Mann, & Leal, 2006). Therefore, lying would imply a greater demand of cognitive resources (Vrij & Heaven, 1999). In this sense, some of the existing stereotypes on the ability of people with intellectual disabilities have lead to the belief that they are not capable of producing complex lies, therefore making them more credible (Bottoms, Nysse-Carris, Harris, & Tyda, 2003). The two stereotypes are contradictory, but both are likely to influence the ability to distinguish truth and falsehood in people with intellectual disabilities. In a previous study (Manzanero, Alemany, Recio, Vallet, & Aro´ztegui, 2015), the differentiating characteristics of true and false accounts made by people with intellectual disabilities were analyzed using procedures based on Reality Monitoring (Manzanero & Diges, 1995; Sporer, 1997), and intuitive ability to discriminate between the two types of stories. The results showed that accounts differed according to their origin in the amount of detail, the incardination of the facts in a spatial and temporal context, and the reproduction of conversations. It was also noted that, from an intuitive point of view, people with little knowledge about developmental disorders and no experience in interacting with people with intellectual disabilities were able to discriminate the two types of statements above chance, but with a high probability of error (0.381). In general, it could be argued that the ability to assess the credibility of a statement is relatively low and tends to be close to random. Most studies (Aamodt & Custer, 2006; Akehurst, Bull, Vrij, & Ko¨hnken, 2004; Bond, 2007; Bond & DePaulo, 2006; Mann & Vrij, 2006; Mann, Vrij, & Bull, 2004; Manzanero & Diges, 1994) show success rates in discriminating between real and false accounts close to 50% with a tolerance of approximately 10%. The percentage of hits would be similar for different groups, depending on their experience (police, judges, students, etc.). The only difference usually found (Bond & DePaulo, 2006; Meissner & Kassin, 2002; Vrij, 2000) is that subjects without training in the analysis of credibility, in general, tend to believe the statements independently from their reality, whereas judges and police are more likely to exhibit mendacity, i.e. they tend to think that accounts are false. However, some previous studies (Ekman & O’Sullivan, 1991; Ekman, O’Sullivan, & Frank, 1999; Ericsson & Smith, 1991) had pointed out that experts in these tasks (such as forensic psychologists, lawyers or the police) would have greater ability to discriminate false testimony from other true statements than subjects with no experience. However, most studies refer to non-significant differences in the ability to detect deception when comparing expert and lay assessors (Bond & DePaulo, 2006; DePaulo & Pfeifer, 1986; Garrido, Masip, & Herrero, 2004; Goodman, Batterman-Faunce, Schaaf, & Kenney, 2002; Kraut & Poe, 1980). Vrij (2004) suggests ten possible causes for the low accuracy in detecting deception: (a) no absolute indicators of lies; (b) subtle differences in lying vs. telling the truth; (c) heuristic decision making; (d) adherence to rules of conversation that hinder detection; (e) reliance on non-diagnostic evidence; (f) attention to channels is not very revealing; (g) dismissal of inter-individual differences in respondents (idiosyncratic error); (h) rejection of the influence of situational factors (intra-individual differences); (i) dismissal of the inter-individual differences of the detectors; and (j) inadequate use of interviewing and interrogation techniques. In addition, limited ability to discriminate may be because actual and false accounts are not sufficiently different (Bekerian & Dennett, 1992; Manzanero, 2006, 2009; Porter & Yuille, 1996; Sporer & Sharman, 2006; Vrij, 2005; Vrij, Akehurst, Soukara, & Bull, 2004), and differential features may appear depending on variables such as retention interval, preparation of narrative (Manzanero & Diges, 1995) or the degree of involvement in the event (Manzanero, El-Astal, & Aro´ztegui, 2009). The aim of this study was to analyze the ability of two groups with different degrees of experience in obtaining and assessing statements (students vs. Judicial Police) to discriminate between actual and simulated victims with ID. According to the ‘‘mendacity’’ bias described above, agents would exhibit a greater tendency to disbelieve the statement provided. Furthermore, this study aims to investigate whether experience influences the assessment of the credibility of a witness. The hypothesis is that the greater the experience, the more accurate judgments about credibility will be. 2. Method 2.1. Participants Two groups of assessors with different experience in obtaining and assessing statements participated in the experiment. The inexperienced group was composed of 53 undergraduate Psychology students (16 men and 37 women) from Universidad Complutense and Universidad de Comillas (Madrid), who had no specific experience or knowledge on how to
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obtain and assess statements (all of them could have participated in civil jury). The average age was 30.32 years (SD = 10.02). They completed a total of 1189 assessments (569 true statements and 620 false statements). The experienced group was composed of 28 police officers who work in special units of the Judicial Police (23 men and 5 women), in charge of investigating crimes against persons. Their main functions/tasks include interviewing and interrogating those involved in these crimes, and therefore have experience in detection (or at least in theory) of lies or inconsistencies in these statements and in performing judgments/assessments about credibility. The average age was 38.5 years (SD = 6.10, interval between 29 and 52) and the average experience in Judicial Police was 10.93 years (SD = 7.98, interval between 2 and 30). To check the degree of experience in the group of policemen was important, subsequently this group was divided into two subgroups. One group was composed of ‘‘veteran’’ police, consisting of 13 officers (12 men and 1 woman) with over 10 years experience in Judicial Police Units (with an average of 18.15 years of experience, SD = 5.03). They performed a total of 361 assessments (167 assessments of true stories and 194 assessments of false stories). The second group consisted of 15 ‘‘novice’’ officers (11 men and 4 women), with less seniority and less than 10 years of service in these specialized units (average of 4 years, SD = 1.88). They performed a total of 402 assessments (184 assessments of true stories and 218 assessments of false stories). Because police officers do not receive specific training to act with people with ID, students who participated in the study had no specific knowledge about intellectual disabilities. 2.2. Procedure As in many cases involving persons with ID, where judicial statements are collected some years later, a real event that took place 2 years ago was chosen for conducting this research – a group of persons with intellectual disability from the Fundacio´n Carmen Pardo-Valcarce went on a day trip, during which the bus they were travelling in caught fire. A researcher selected the people with ID who had given statements using a truthfulness criteria: ‘‘real victims’’ for those who went on the day trip or ‘‘simulated victims’’ for those who did not go on the day trip but knew about the event from references made to it. The two groups were of comparable IQ (see Table 1). All persons with ID who participated in the study (or their legal guardian) signed consent for voluntary participation. All persons with ID were informed of the purpose of the research and were given instructions. Simulated victims who did not go on the day trip were given a summary of the most important information about the day trip, such as its location, the main complication on the day trip, and the course of the day. To increase the ecological validity of our study, all people in the two groups were encouraged to give their testimonies as best they could. While they were not put under the stress of making the interviewer believe their testimony (to prevent undue tension in the interview), we decided to invite them to a soda if they succeeded in convincing the interviewer that they had, in fact, experienced the event. As can be observed in Table 1, each condition consisted of more than 10 stories, as is suggested in previous research, because if the number of reports is small, the possibility of obtaining results by chance increases significantly. Frank and Feeley (2003) advise, in line with other detection of deception researchers, that the number of statements to be assessed in a detection test should be close to 10. Two investigators, ‘‘blind’’ to the real or simulated victim condition, experts in interviewing and obtaining victim testimonies, conducted interviews individually with each ‘‘victim’’. All interviews were audio-visually recorded. Interviews were always conducted following the same instructions: ‘‘We would like you to tell us everything that happened, from beginning to end, with as many details as possible, when you went on that day trip where the bus burned down. We want you to tell us everything, even the things that seem unimportant’’. Once the free account of the incident was obtained from all participants, they were asked the same questions: Who were you with?, Where did it happen?, Where were you going?, What did you do? and What happened afterwards? The order of the interviews was randomized. Each victim was interviewed only once, since if they were to be interviewed more than once, there would be the risk of not judging them on the veracity of the statement, but rather on the consistency of their behaviour shown in each different session. The statements had a mean duration of 5 min and 15 s (SD = 2.3027), with the shortest interview lasting 2½ min and the longest 12 min and 26 s. Their duration is considered sufficient to issue credibility judgments, since very short statements (under 2 min) may lack, especially in subjects with intellectual disability, enough items on which to base a judgement. Once obtained, the statement videos were edited so that none of them gave any explicit indication as to which group the victims
Table 1 Frequencies of true and false statements and characteristics of the two ‘‘victims’’ groups. True statements N = 13
Mean IQ: 60.72 (SD = 9.67) Range IQ: 50–78 Mean age: 35.18 (SD = 7.16)
False statements N = 16
Mean IQ: 59.30 (SD = 9.44) Range IQ: 48–80 Mean age: 33.75 (SD = 6.78)
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Table 2 Frequencies and percentage of hits (H), correct rejections (CR), false alarms (FA) and omissions (O) obtained by each group. Evaluation
Origin of the statement Simulated
Real
Inexperienced (students)
Lie Truth
CR: 404 (65.16%) FA: 216 (34.84%) 620 (100%)
O: 197 (34.62%) H: 372 (65.37%) 569 (100%)
Experienced (police)
Lie Truth
CR: 268 (58.64%) FA: 189 (41.35%) 457 (100%)
O: 130 (33.50%) H: 258 (66.49%) 388 (100%)
belonged to (for example, ‘‘actually, what I’m telling you is not true. I know I do not have to lie’’). Three interviews in the ‘‘false’’ group were discarded because the victims were not able to follow the instructions. The videos of the true and false victims were shown on a large-format screen. All assessors attended the screening at the same time, but they were prevented from interacting among themselves in order not to bias each other while making their individual assessments. The videos were shown in random order to prevent a learning effect from differentially impacting their ability to evaluate true and false statements. After each video was shown, the assessors were asked to categorize the victim as true or false. The general instructions given were as follows: ‘‘Next, a series of videos will be shown in which people with intellectual disability are giving a statement about a bus accident. Some of the statements were given by individuals who had actually experienced that event; the others were given by individuals who, although they had not experienced the event directly, had been told about the event, and have given their statement with the intention of making us believe they had experienced the accident. Your task is to decide who is an actual victim and who is a simulated victim. As you are assessing each victim, bear in mind that the interviewees are all persons with intellectual disability, so their way of telling things may be peculiar/different.’’1 In order to measure the accuracy with which each of the two groups of assessors evaluating the credibility of the victims, measures of accuracy (hit, false alarm, correct rejection and omission), the discriminability index d0 , c response criteria from Signal Detection Theory (Tanner & Swets, 1954) and the overall percentage of hits and mistakes, were used. 3. Results 3.1. Intuitive assessment of credibility The analysis of the credibility assessments made from intuition shows that the inexperienced group is able to discriminate between real and false statements above chance, as the discriminability index d0 was 0.785 (SD = 0.075), Zd = 10.492; p < 0.05. Whereas the response criterion c yielded a score of 0.003 (SD = 0.037), Zc = 0.078; p = n.s., which would indicate it would not be different from a neutral criterion. The percentage of correct classifications was 65.26%. The analysis of the credibility assessments made from intuition shows that the Judicial Police officers are able to discriminate between real and false statements also above chance, as the discriminability index d0 was 0.644 (SD = 0.088), Zd = 7.285; p < 0.05. Whereas the response criterion c yielded a score of 0.104 (SD = 0.044) Zc = 2.347; p = n.s., indicating a neutral criterion. The percentage of hits was 62.24%. Table 2 shows the frequency and percentage of hits (H), correct rejections (CR), false alarm (FA) and omissions (O) obtained by each group. The results show that the performance of the officers of the Judicial Police of the Guardia Civil is not statistically different from that obtained by the control group. There were no significant differences in effectiveness in discriminating between true and false statements between police and students (Z = 1.219, p = n.s., Cohen’s d = 1.724, r = .653). Fig. 1 shows the ROC curves (Swets, 1986) on the discrimination ability of Judicial Police and students. On the other hand, the hypothesis regarding officers tending not to believe the statement provided (mendacity bias reflected in other research with police) is not confirmed, and the criterion (c) scores obtained show that both, the experienced and the inexperienced group, present a neutral response criterion. 3.2. Distinction amongst officers of the Judicial Police in light of experience In order to check if the years of experience influence the results, the analysis of the intuitive assessments of the two subgroups within the group of experts is presented below. Table 3 shows the results of accuracy obtained in the credibility judgments by the group of ‘‘veteran’’ and ‘‘novice’’ officers.
1 In and of itself, the obvious disability of persons with ID could be one of the indicators on which the students based their intuitive assessments. Correlations were made between the statements the students intuitively evaluated as true and the IQ of the persons with ID who gave those statements, and the results showed a null correlation (r(23) = 0.006, p = n.s.).
[(Fig._1)TD$IG]
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Fig. 1. ROC curves of the discrimination ability of police officers (left) and students (right).
The analysis of the credibility assessments made from intuition shows that ‘‘veterans’’ are able to discriminate between real and false statements above chance, as the discriminability index d0 was 0.721 (SD = 0.136), Zd = 5.323; p < 0.05. While the response criterion c reached a neutral criterion, with a score of 0.032 (SD = 0.068) Zc = 0.470; p = n.s. The percentage of hits was 63.98%. The analysis of the credibility assessments made from intuition also shows that the ‘‘novice’’ officers with less than 10 years of experience in Judicial Police, are able to discriminate between real and false statements above chance, as the index discriminability d0 was 0.582 (SD = 0.128), Zd = 4.562; p < 0.05. While the response criterion c reached a score of 0.071 (SD = 0.064) Zc = 1.110; p = n.s., indicating a neutral criterion. The percentage of correct classifications was 61.19%. The difference between ‘‘expert’’ and ‘‘novice’’ officers indicates that agents that have greater seniority in the JP specialty do not show greater accuracy as the discriminability does not differ significantly (Z = 0.744, p = n.s., Cohen’s d = 1.052, r = .466). 4. Discussion From the data obtained in the present study, it is clear that no significant differences were found in terms of experience to discriminate between groups while assessing true and false statements issued by people with intellectual disabilities. These data show that the ability to discriminate between these two groups based on their experience and knowledge to obtain and assess statements produced over 60% of hits of the statements, though this percentage is close to random. Therefore, the present study supports previous studies that highlight the absence of differences between experienced and inexperienced assessors in discriminating between true and false statements issued by people without ID (Bond & DePaulo, 2006, 2008; DePaulo & Pfeifer, 1986; DePaulo, Stone, & Lassiter, 1985; DePaulo, Zuckerman, & Rosenthal, 1980; Goodman et al., 2002; Kraut, 1980; Kraut & Poe, 1980; Vrij, 2000; Vrij & Graham, 1997). And in turn, our results do not support the studies that have shown that police experience improves performance in lie detection (Ekman & O’Sullivan, 1991; Ekman et al., 1999). Hence, we must conclude that experience is not sufficient to discriminate between real and simulated victims with ID and when the event took place a long time ago, and that specific techniques that help perform this task with a lower error rate should be enhanced. These techniques should focus mainly on decreasing the false alarm rate, which is around 40% of the classifications of false statements. This is necessary to reduce the consequences for law enforcement resulting from the results of this research, if they were to be extrapolated to cases of real/actual research that could lead to the arrest of an innocent person. Previous studies may shed some clues on the cognitive basis that explain this excessive false alarm rate in the assessment of statement made by people with ID. Manzanero et al. (2015) showed how people with ID narrated an experience they had not lived in a way that assessors tended to categorize these stories as true. Furthermore, sometimes trying to remember Table 3 Accuracy obtained in credibility assessments issued by ‘‘veteran’’ and ‘‘novice’’ officers. Evaluation
Origin of the statement Simulated
Real
Veteran police
Lie Truth
CR: 122 (62.89%) FA: 72 (37.11%) 194 (100%)
O: 58 (34.73%) H: 109 (65.27%) 167 (100%)
Novice police
Lie Truth
CR: 128 (58.72%) FA: 90 (41.28%) 218 (100%)
O: 66 (35.87%) H: 118 (64.13%) 184 (100%)
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information from an episode (e.g. an event occurred in distant time) may require more cognitive effort than inventing it, as a false statement may very well correspond to a prototype scene or mindset that occurs following a script and that does not require a cognitive effort or at least less effort than a genuine memory. Therefore, an essential process in the formation of police technicians who must work on testimonies of people with ID in relation to reducing false alarms is to alert them that disability does not inoculate against the production of false testimony: people with ID may have an ability to develop false statements that do not differ from how people without ID tell them. As for the results obtained regarding the absence of significant differences in the performance of experienced and novice police officers, this work highlights the need to study how the variable ‘‘experience’’ is operationalized, and whether the training received and the specific functions perform may be influencing and compensating for the lack of years of service with different skills. Usually, and also in this study, experience is measured only in number of years served and does not take into account other indicators related to the quality and intensity of work during those years. 5. Conclusions From the present study, the reflection on the procedure followed within the police and judicial field in cases in which the credibility of the testimony of a person with intellectual disabilities must be assessed seems necessary. In light of the obtained results, it is clear that intuition is not a good way to assess the testimony credibility of these victims, in the case of civil juries inexperienced in obtaining and evaluating statements, but not even in cases where the professional has experience in evaluating testimonies as part of their daily work. The lack of success in discriminating between real and fake statements by intuition could be solved with the use of specific techniques for analyzing credibility. The main problem that we face in the field of analysis of testimonies of people ˜ oz, Sotoca, & Manzanero, with ID is that, so far, such techniques have not been adapted to people with ID (Gonza´lez, Mun 2013), such as the use of the Criteria-Based Content Analysis (CBCA) in the case of children with normal development (i.e. Stro¨mwall, Bengtsson, Leander, & Granhag, 2004). This system of credibility assessment based on memory processes is the most established and researched. It has two criteria known as ‘‘unstructured production’’ (spontaneous reproduction) and ‘‘amount of details’’ (or sufficient details), which seem responsible for distinguishing between honest and false statements. This is because the memories of external events are more detailed and have a looser, more spontaneous structure than memories derived from imagination or fantasy. However, the data obtained in this research show that they are far from being effective, so it is necessary to devote all efforts in developing specific tools tailored to victims with ID. Not to mention that, as highlighted in this paper, people with ID probably issue statements from which it is not possible to obtain such a spontaneous and detailed account as is desirable due to their cognitive and communication difficulties. Among the usual difficulties in analyzing testimonies of people with ID within a police environment are those characteristic to the victim that interfere with his/her statement: low self-esteem, poor social skills, dependence, acquiescence, ‘‘submission’’, etc. That is, a number of factors that make these individuals very vulnerable and prone to suffer abuse (Joyce, 2003). In this sense, participants in this study had no specific knowledge about intellectual disabilities. Note that police officers do not receive specific training to act with people with ID. Future studies could consider the importance of this knowledge in the development of credibility judgments. Therefore, until research does not demonstrate the effectiveness/reliability of other credibility indicators, the testimony of these victims should be taken as just another indication and should be contrasted with other sources of information available to the researcher. In summary, it is necessary to provide adequate resources and standardized procedures to adequately treat people with ID who come into contact with police and judicial institutions. These resources must be provided by specialized organizations serving these groups and the State Administration, both from the police and the judicial side. This work demonstrates the need to invest in effective policing procedures for the group of people with ID. Acknowledgements We thank the people with intellectual disability in the Employment Workshops and Occupational Workshops of the Carmen Pardo-Valcarce Foundation, who collaborated in the study by providing real and false stories for further analysis. This work is part of research project entitled The witness evidence in specially vulnerable victims, developed by the UCM Research Group on Psychology of Testimony. References Aamodt, M. G., & Custer, H. (2006). Who can best catch a liar? 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