Our court system assumes that people can tell whether other people are telling the truth by evaluating the demeanor of the other people. This is true in a wide range of contexts. Jurors are encouraged to consider the demeanor of each witness in deciding whether to credit the witness's testimony. N.C.P.I. -- Crim. 101.15 (referring to the "manner and appearance" of the witness). When judges must determine facts, their fact-finding is reviewed deferentially because they had the opportunity to assess the demeanor of the relevant witnesses. Yurek v. Shaffer, __ N.C. App. __, 678 S.E.2d 738 (2009). An officer's assessment of a suspect's demeanor -- like whether the suspect appeared to be nervous -- may be a factor in deciding, for example, whether the officer was entitled to detain the suspect for further investigation. State v. Jacobs, 162 N.C. App. 251 (2004). It turns out that this assumption is mostly false. There's a wealth of social science research on lying and lie detection, and "[t]he 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." Maria Hartwig, et al., Detecting Deception, Law and Human Behavior (Aug. 2005). As the quoted language suggests, police officers aren't much better than laypeople at detecting lies based on behavioral cues. Nor do people who express confidence in their prowess at lie detecting perform any better than average. Part of [...]
Faculty Coordinators
