Forensic expectations: Investigating a crime scene with prior information

In a large body of research the influence of contextual information on decisions made in a broad range of disciplines has been studied. To date, the influence of these expectancy effects on the crime scene investigation has not been studied. In the present study we explored the effect of prior information given to crime scene investigators on their perception and interpretation of an ambiguous crime scene. Participants (N=58) were experienced crime scene investigators who were provided with a panoramic photograph of an ambiguous mock crime scene. The victim may have committed suicide or was murdered. Participants either received prior information indicating suicide, prior information indicating a violent death, or they received no prior information. Participants were asked about what they thought had happened at the scene of the crime, both at the initial assessment of the scene and at the end of the investigation when they were asked to describe the most likely scenario. They were also asked which traces they wanted to secure and why. Results showed that participants interpreted the crime scene differently dependent on how it was presented to them. Both the initial assessment of the scene and the most likely scenario that was described after the investigation were influenced by the prior information the participants were provided with, even though roughly the same traces were secured by all, independent of the prior information. Results demonstrate that prior information indeed influences the interpretation of the crime scene, but since the present study was exploratory further research is needed.