This text, Psychology and Law: Truthfulness, Accuracy and Credibility, provides a comprehensive review of relevant topics as far as determining the accuracy of a witness, victim or suspect is concerned. Each chapter not only focuses on relevant research but also presents readers with a detailed understanding of the research methodology, the theoretical perspectives, the shortcomings of the research/ theory and the practical significance of the findings.
Chapter 2 examines the characteristics of liars. Nonverbal, verbal and physiological cues (such as the polygraph) to deception are described together with a discussion of what professional lie catchers believe to be cues to deception and of their ability to detect deceit. We discuss the reasons why professional lie catchers (and people in general) make mistakes while attempting to detect deceit. We also examine the social contexts in which lying occurs and people's reasons for lying. Liars are said to experience three processes during the time that they are engaging in deception (and probably afterwards, too), and much of the research literature is organised around the study of these three processes. The first is an emotional reaction (such as guilt, fear and excitement), and this can independently influence behaviour. For example, guilt may sometimes result in gaze aversion. The second is “cognitive overload” arising from the difficulty of maintaining deceitful behaviour. This can result in disturbances in speech content, gaze aversion and other behaviours. The third process is behavioural control or impression management. This can suppress the behaviours that liars believe may “give away” a lie (for example, a reduction in hand movements). We argue that behavioural cues to deception may become visible only if a liar substantially experiences at least one of these three processes. The bulk of research in this area is laboratory based. However, there are some examples of deception detection in high-stake real-life situations. For example, we describe an analysis of former US President Bill Clinton's behaviour during his testimony before the grand jury in 1998 about his alleged sexual affair with Monica Lewinsky. We also report an in-depth study of the behaviour displayed by 16 suspects who were interviewed by the police in connection with serious crimes such as murder, rape and arson (Mann, Vrij & Bull, 2002).
We end Chapter 2 by concluding that no perfect lie detection test exists, and that lie detection experts make wrong judgements on a regular basis. However, there are detection methods which enable lie detectors to determine whether someone is lying or telling the truth above the level of chance, and these may assist investigators in early stages of their investigation.