Lie Detection in a Forensic Context

Lie detection is a major theme in “psychology and law,” which in turn is one of the main areas of applied psychology. Indeed, it is not difficult to understand why it is important to know whether someone is lying or telling the truth in police investigations, court trials, border control interviews, intelligence interviews, and so on. To aid lie detection, psychologists and practitioners have developed numerous lie detection tools. Such tools span the entire possible range from observing behavior, analyzing speech, and measuring peripheral physiological responses to recording brain activity. This article will introduce the reader to the main lie detection tools used to date. After presenting general overview texts about the topic, the article will briefly introduce the history of lie detection, followed by a presentation of the main theories that underpin lie detection tools. Attention will also be paid to liars’ efforts to fool those who try to detect their lies, as well as to an important technical issue: how to test the accuracy of these lie detection tools. The accuracy of lie detection tools can easily be tested in controlled laboratory settings, but lying in such settings is somewhat artificial. For example, examinees lie for the sake of the experiment, and their lies are condoned. The problem of testing the accuracy of lie detection tools in real-life field cases is that it is virtually impossible to determine with certainty when someone is lying and when he or she is telling the truth. This article also discusses the various lie detection tools. All tools face the same problem: a cue uniquely related to deception, such as Pinocchio’s growing nose, does not exist. It means that there is not a single cue (or cluster of cues) investigators can really rely upon. It also means that errors are frequently made when those tools are used. Lie detection without the use of tools is perhaps even more difficult, but a debate is going on as to whether some people have extraordinary skills to detect lies. After focusing on this “wizards in lie detection” debate, the article concludes by discussing two recent important developments in lie detection research. The first is “interviewing to detect deception” research. The key issue is that investigators can make the task of lying more difficult for interviewees, which, in turn, facilitates lie detection. The second is lie detection research specifically aimed at intelligence settings. It raises specific questions that have not been addressed in and cannot be answered by the traditional “police investigations” deception research.