Impacts of physical and testimonial evidence on South Korean Police interrogator’s selection of tactics

Interrogators can hold various types of evidence that influence investigative decisions. This study examined the effect of evidence type on interrogators' tactic selection. A mixed design was used, randomly assigning 106 South Korean police interrogators to one of five evidence conditions (DNA, CCTV, fingerprint, eyewitness, or no evidence). Participants read a homicide case report where the critical evidence was manipulated with one of the five evidence types, but all other details remained consistent. They selected tactics from a list of 27 tactics, categorized as evidential (e.g. gradual evidence disclosure) or non-evidential (e.g. rapport-building). The proportion and number of tactics chosen served as dependent variables. Results show that South Korean interrogators in this experimental setting preferred non evidential tactics, such as active listening and identifying basic needs and emotional state, more frequently than evidential ones. Additionally, these non-evidential tactics were reported to be commonly employed in their routine interrogations.