The Impact of Evidence Type on Police Investigators’ Perceptions of Suspect Culpability and Evidence Reliability

Abstract

Abstract. In a repeated-measures experimental study, we examined how evidence type influences police investigators’ beliefs about (a) suspect’s culpability and (b) reliability of incriminating evidence. South Korean detectives ( N = 202) read four crime reports including general information about a crime and a suspect. In the general case information, one piece of critical and several pieces of noncritical evidence collected during the investigation were presented. Officers read four simulated reports of crimes, and in each report, they were given one piece of evidence linking the suspect to the crime. We manipulated the critical evidence identifying the suspect with four evidence types: CCTV, DNA, fingerprint, and eyewitness testimony. We found that evidence type influenced detectives’ judgments about suspect’s culpability and evidence reliability, such that when eyewitness (vs. CCTV, DNA, fingerprint) evidence was given as critical evidence, officers were more likely to think that the suspect was less culpable and that the evidence was less reliable. Theoretical and legal implications of these results are discussed.