Police and Investigative Psychology
This domain tests interviewing, confession risk, deception detection and eyewitness identification - the points where investigative practice most directly shapes evidence.
Interviewing
Accusatory, guilt-presumptive methods such as the Reid technique increase pressure and confession risk. The PEACE model (Planning and preparation, Engage and explain, Account, Closure, Evaluate) is standard in England and Wales and underpins the cognitive interview: reinstate context, report everything, vary retrieval order, change perspectives.
False confessions
Kassin and Wrightsman (1985) distinguish voluntary, coerced-compliant (to escape the situation) and coerced-internalised (the suspect comes to believe in guilt) confessions. Risk factors include youth, intellectual disability, sleep deprivation, lengthy interrogation and false evidence ploys.
Detection and identification
Behavioural deception detection averages near chance (Bond and DePaulo, 2006); no reliable nonverbal cue exists. Eyewitness accuracy depends on estimator variables (lighting, weapon focus, cross-race effect) and system variables under police control (lineup composition, instructions, blind administration, sequential versus simultaneous presentation). Post-identification feedback inflates confidence without improving accuracy.
Worked example
A witness identifies a suspect from a lineup whose five fillers do not match the description. Functional size is close to one, so the identification has near-zero probative value regardless of how confident the witness appears.
Traps
Assuming training lifts deception accuracy to 80-90%; treating offender profiling as evidence rather than investigative support; believing confident witnesses are accurate; and ignoring contamination by pre-lineup discussion or post-identification feedback.