Effects of evidential and non-evidential interrogation techniques on suspects' perception of evidence in South Korea

Interrogators use diverse techniques, and suspects try to analyze these to infer the amount of police evidence (perception of evidence). However, the link between technique types and the perception remains understudied. We examined perceptions of 27 evidential (e.g., disclosing evidence) and non-evidential (e.g., rapport-building) techniques in Study 1 (N = 59 prisoners/detainees) and Study 2 (N = 117 laypersons). We predicted evidential techniques would elicit higher perceived police evidence than non-evidential ones. This hypothesis was partially supported in both studies: evidential techniques involving substantiated claims consistently yielded higher perceived evidence than non-evidential techniques; however, unsubstantiated evidential techniques did not consistently differ from non-evidential ones in perceived evidentiary value. Exploratory comparisons further revealed that detainees and prisoners perceived non-evidential/crime-irrelevant techniques as indicative of significantly less police evidence than laypersons, with broader perceptual variability observed across numerous individual techniques.