Asymmetries in Prior Conviction Bias (Presentation Slides)

Abstract

This paper summarises the theory and method behind the findings of paper: Cowley, M., & Colyer, J. B. (2010). Asymmetries in prior conviction reasoning: Truth suppression effects in child protection contexts, Psychology, Crime and Law, 16(3), 211-231. to make its quantitative findings more accessible to law and criminology student readerships. The premise behind examining prior conviction evidence as a biasing psychological construct, i.e. a mental representation held in mind that can take over a set of evidence rather than act as an additive probative value, is outlined. The results of three mock juror studies are summarised in which prior conviction evidence for violent offences, or prior conviction evidence for sexual offences, was disclosed. Some of the results are quite emphatic, and show that jurors will move towards guilty verdicts for as little as evidence of defendant handedness corroboration, when a defendant's prior conviction for a similar violent offence is disclosed. What's more, the results show that where prior conviction evidence is disclosed, the volume of available alternative explanations of the evidence offered by jurors is significantly reduced. The main interpretation of such a finding is that a mental representation is being held in mind for such evidence, rather than a smaller psychological construct or thought component. The implication is that the psychological weight ascribed by jurors to prior conviction evidence may go against any prescriptions of legal instruction (e.g., Criminal Justice Act, 2003; Chapter 11). The presentation slides outline the full methodology in easy to read graphs and summaries, and draws some inferences about the implications for the soundness of verdicts in such contexts.