Choice and Background Knowledge: How do Individuals Evaluate Accumulating Evidence in A Murder Scenario?

Elizabeth Mackenzie,Matthew Roberts,Emily Chalmers,Piers Duncan,Colin Wastell

doi:10.5539/ijps.v10n2p1

Elizabeth Mackenzie, Matthew Roberts + Show 3 more

Open Access

https://doi.org/10.5539/ijps.v10n2p1

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Abstract

Can the simple act of selecting a possible suspect of a crime bias the evaluation of the evidence? Does the typicality of the crime impact the assessment of guilt of a suspect? In two experiments, we examine these two questions and find some remarkable results with implications for law enforcement and jury deliberation. Experiment 1 data show that by allowing participants to choose a most-likely-perpetrator, guilt ratings were substantially higher compared to participants who were not allowed to make a choice. This difference persisted after reading a further body of incriminating evidence. In experiment 2 participants were provided with general and specific background information relevant to a suspect, in other words how common was the crime-suspect scenario. When provided with high plausibility compared to low plausibility information, participants gave higher guilt ratings that persisted after further evidence. The results are interpreted in terms of argument theory which provides a parsimonious explanation of the data. These results have implications for the conduct of investigations, for example: putting in place procedures that minimize the effects of suspect prioritization and background information.

Highlights

The investigation of crime requires the most stringent application of rigorous methods of reasoning and evidence evaluation
Criminal investigators and members of juries are subject to the heuristics and biases that are characteristic of the general public, and so must make greater efforts to minimize their impact on the evaluation of evidence when forming a judgment
Guilt ratings greater than two standard deviations from the mean initially, following a body of incriminating evidence (BIE), the final piece of evidence (FPE)-I or FPE-N were excluded from analysis (Field, 2013)

Summary

Introduction

The investigation of crime requires the most stringent application of rigorous methods of reasoning and evidence evaluation. Decades of research into human reasoning and judgment have shown that human beings are subject to biases, and that they utilize heuristics in order to cope with information rich environments in an adaptive manner (Gigerenzer, Hertwig, & Pachur, 2011; Gilovich, Griffin, & Kahneman, 2002). Criminal investigators and members of juries are subject to the heuristics and biases that are characteristic of the general public, and so must make greater efforts to minimize their impact on the evaluation of evidence when forming a judgment. In order to be more rigorous, criminal investigators apply systems of evidence evaluation that aim to minimize the negative effects of ordinary human information processing predispositions. Police investigators have shown a tendency to decide, very early in an investigation, on the most likely suspects and target their investigation against those suspects (Keppens & Schafer, 2006; Sedly, 1993)

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