Criminal psychology

1. DETECTING DECEPTION
Desmond Ayim-Aboagye, Ph.D.
Criminal Psychology

2. Overview
• Detecting deception from behavioural
cues
• A number of books have been published that claim to reveal
• behavioural cues to lying. Some have focused on the criminal
• setting and have been based on experienced investigators’
• beliefs about such cues. Unfortunately, recent criminal psych-
• ology research has found much of what such books claim to be
• signs of deceit to be mistaken. That is, although relevant
• professionals and lay people in several countries share the same
• beliefs about supposed cues to lying, these beliefs are largely
• wrong. In this section we will look first at the beliefs and then at
• the reality.

3. Beliefs about cues to lying (indicators of
nervousness)
• Behavioural cues to lying reported:
• * that people think liars avert their gaze more (i.e. look you in the eye less),
• *move their hands and feet more,
• *shift their body position more,
• *gesture more and touch their own body more.
• The reason why people think this probably relates to the fact that such behaviors
are fairly useful indicators of nervousness. If liars are nervous then they may
• behave like this.

4. Reasons for rejection
• Many of the beliefs about signs of deceit rest on the assumptions that w
hen people lie they experience emotion and they may
• have to think about the lies
• Reasons for rejection:
• 1. People telling the truth may well become emotional
• 2. Innocent suspects can be emotional
• 3. Some criminals may not be emotional about their crimes or
• during police interviews. They may well also have taken time to prepare and pra
ctise their lies so that they come to mind easily.
•

5. Important
• Detecting lies from behavioural cues demonstrated that they are
• typically little or no better than chance at this.
• A recent overview of many dozens of previous, world-
• wide studies concluded that there are no perfectly reliable behav
ioural cues to deception.

6. How good are professionals at detecting
deception from behaviour?
• According to Professor Aldert Vrij of the University of
Portsmouth Performance to date seems far from perfect.
• There have been researches in both USA and Britain. No
conclusive evidence exist. Read the research reports analyzed
in your book in chapter six.

7. Why can’t they detect deception?
• Professor Vrij has suggested some reasons that are based on
Psychological Theory and research
• 1. First, and perhaps foremost, there are dozens of research
• studies on how people actually behave when lying, which consist-
• ently have revealed that when lying compared to when they are
• telling the truth some people show increases in certain behav-
• iours, while other people show decreases or no change in the same
• behaviours.
• 2. Furthermore, in some lying/truth-telling situations a
• person’s behaviours may increase, but the same person’s behav-
• iours may decrease in other deceptive situations.

8. Several Possible Reasons
• 1. One is that when the stakes are higher ( as
• in our study involving real-life police interviews with suspects)
• emotions may be stronger, thus affecting behaviour more.
• 2. Another is that many people when lying try hard not to give off the
• cues they believe people look for in liars (e.g. increases in
• behaviour), and they either succeed in this or they over-control
• their behaviour, resulting in decreases.

9. Several Possible Reasons
• 3. Yet another might relate to whether liars have had time to prepare/practise th
eir lies. When we analysed the behaviour of the police suspects in our study we
• found lying to be associated not with the cues people commonly
• believe in (see the above section) but with a decrease in blinking
• and in hand/arm movements (females) and an increase in
• speech pauses.
• 4. A further reason why many professionals seem
• poor at lie detecting is that they may concentrate their efforts on
• analysing people’s behaviour (especially facial cues - some of
• which are, in fact, among the easiest for liars to control) rather
• than on their speech content and on how they say it. Such a focus
• would seem counterproductive if speech cues are better guides to
• lying (see the section below).

10. Several Possible Reasons
• However, if the police conduct
• interviews with suspects in ways that do not effectively encourage
• the suspects to speak (see chapter 4), they will produce fewer
• speech cues. This is one reason why police interviewers who are
• unprepared and not properly trained may often make lie detec-
• tion mistakes when interviewing suspects (e.g. letting a guilty
• person go free).

11. So how might professionals become better lie detectors?
• 1. First of all, they need proper training on how to conduct information gath-
• ering investigative interviews (see chapter 4)
• 2. Secondly, they need
• training (based on the results of relevant, published, quality
• research rather than on speculation) to avoid relying on the stereo-
• typical but wrong cues (see above), and guidance on which cues
• can be better guides, with the clear acknowledgement that even
• these cues are not that reliable as indications of lying.
• 3. Furthermore, they need training to overcome other false beliefs such as (i) honest or attra
ctive-looking people lie less and (ii) people who look
• nervous are liars (when they are probably just socially anxious or
• introverted).
• 4. Then, they need to understand that if professionals
• behave in an accusatory or aggressive or suspicious way this in itself
• may well result in the person giving off cues that the professionals
• believe to be signs of lying.

12. So how might professionals become better lie detectors?
• 5. They also need training to combine
• useful cues from behaviour and from speech (see the section below
• on combining lie detection methods).
• 6. Finally, they need guidance
• on how to avoid revealing near the beginning of the interview most
• or all of the information they have about the crime and the suspect
• (see chapter 4).

13. Training to detect deception from behaviour
• Canadian parole officers and students received training that involved:
•
• A) myth dissolution (information that common beliefs about
•
• cues to deception are usually wrong)
•
• B) describing the cues that some research studies have found to
•
• indicate lying in some people
•
• C) feedback on how accurate were their lie detection decisions.

14. Detecting deception from speech content
criteria-based content analysis
• In Germany in the 1950s the Supreme Court was concerned about
• relying on information provided (solely) by one or more young
• children to convict someone of the very serious crime of child
• sexual abuse.
• Therefore, it endorsed the idea that relevant experts
• (who are court appointed in the German inquisitorial criminal
• justice system) analyse such children’s accounts for indications
• that the children may well be describing genuinely experienced
• events.
• This analysis is usually referred to as criteria-based
• content analysis (CBCA).

15. Criteria-Based
Content Analysis (CBCA).
• This analysis is part of ‘Statement
• Validity Assessment’, which courts in Germany, Sweden and the
• Netherlands have been using to guide their decisions. CBCA is
• based on a number of sensible assumptions, among which are that
• statements (i.e. the contents of what a person says) derived from
• memory of actual experiences differ in quality/content from those
• based on fabrication.

16. Nineteen different criteria
• These criteria relate to:
• (i) general characteristics of the statement (e.g. the
• amount of detail),
• (ii) specific contexts (e.g. reproduction of conversation, unexpected co
mplications during the incident),
• (iii) motivation related contents (e.g. the child spontaneously correcting
herself when giving her statement - something which liars may
• worry about doing) and
• (iv) details characteristic of that type of
• offence (e.g. that the child was ‘groomed’ before being abused).

17. Computer Analysis
• A recent development in the analysis of speech to detect deception
• involves the use of computer software to analyse written tran-
• scripts of what people say. (These transcripts are written by
• humans who listen to tape recordings of people lying and telling
• the truth.)
• The software allocates each word spoken to a category
• (e.g. spatial, affective, cognitive) that theoretically may relate to
• lying/truth-telling in a way similar to the reality monitoring
• approach (see above).
• The software can also allocate the words to
• linguistic categories such as ‘negative emotions’ and ‘first person
• singular’ (e.g. I, me, my).

18. Computer Analysis
• The software can also allocate the words to
• linguistic categories such as ‘negative emotions’ and ‘first person
• singular’ (e.g. I, me, my). However, at present the software has
• quite a high error rate (of around twenty per cent - which is not
• better than trained humans)
• Nevertheless, a recent study of prisoners lying and telling the truth abo
ut what happened in video clips that they had just seen found that thes
e types of automatic computer-based transcript analyses to have a trut
h/lie detection rate significantly better than chance.
• However, a few word cate-
• gories occurred more frequently in the way opposite to that
• predicted (e.g. more spatial words while lying). Clearly, more
• research is needed.

19. The polygraph
• A polygraph test is used in to detect deception.
• The set of equipment known as the polygraph (from the Greek
• poP = ‘many’ and graph = ‘to write’) measures various sorts of
• internal bodily activities such as heart rate, blood pressure, respir-
• ation and palmar sweating.

20. Polygraph
• These activities are displayed on charts or on computer screens.
• Such equipment is used in many medical and scientific settings. Its use in attem
pting to detect deception is based on the age-old assumption that lying is accom
panied by changes in such internal bodily activities.
• While the equipment does measure such activities with great accuracy, the
• big issues for polygraphic lie detection are:
• (i) whether deceivers’ bodily activities are reliably different when lying than when
truth- telling and
• (ii) whether such differences do not similarly occur in
• truth-tellers (e.g. an innocent man being questioned about the
• murder of his wife with whom he was experiencing severe marital
• difficulties).

21. Polygraph Test
• A polygraphic lie detection tests focus on the
• following topics:
•
• • how to determine if a testing procedure can be relied upon;
•
• • its use in criminal investigations;
•
• • its use in security screening.

22. Psychologists and polygraph test
• Psychologists around the world have devoted decades of effort to :
• (a) establishing and publicizing how best to determine if tests can
• be relied upon and
• (b) assessing the quality of many thousands of
• tests. This is vitally important work. Just because a person or organ-
• ization claims to have developed a useful test does not mean that
• the test is a good one. Many issues are relevant but the most
• important ones are reliability and validity.
•
• Within psychology reliability refers not to accuracy but to
• similarity across time or among testers. It is the issue of validity
• that is closest to accuracy.

23. There are several aspects of reliability:
• • ‘inter-examiner’ reliability which focuses on whether different
• testers make similar judgements to each other when assessing
• the same person
•
• • ‘test-retest’ reliability which focuses on whether when re-tested
• a person receives a similar judgement as when first tested
•
• • ‘inter-item’ reliability focuses on, for example, whether the
• various questions put to the person taking the test lead to the
• same conclusion.
•

24. Reliability
• Validity is concerned with the extent to which a test assesses
• what it claims to assess. It too has several aspects:
•
• • face validity is the extent to which a test ( on the face of it) looks
• like it assesses what it claims
•
• • content validity is concerned with the relationship of the con-
• tents of the test to the phenomenon being assessed
•
• • construct validity concerns the relationship of the test to
• underlying theories/constructs concerning the phenomenon

25. Reliability
•
• • criterion validity is the extent to which scores on the test actu-
• ally predict outcomes (e.g. how accurate the procedure is at
• classifying people as lying or truth-telling)
•
• • incremental validity concerns how well a test compares with
• other tests that have been designed to examine the same phe-
• nomenon (e.g. detecting deceit).

26. Recommended Reading
• Ainsworth, P. B. (2000) Psychology and crime: Myths and reality.
• Harlow, Essex: Longman.
•
• Alison, L. (2005) The Forensic Psychologist’s casebook: psychological
• profiling and criminal investigation. Cullompton, UK:
• Willan.
•
• Carson, D. and Bull, R. (2003) Handbook of psychology in legal
• contexts, 2nd edn. Chichester: Wiley.