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Experimental Psychology Seminar

Why does pre-trial detainment increase conviction rates? An empirical study.

(Stephen Dewitt, Experimental Psychology, UCL)

Naturalistic research has shown that defendants who are denied bail (detained pretrial) are more likely to be found guilty at trial and receive harsher sentencing. The purpose of our study was to test experimentally whether pre-trial detainment would influence participants’ beliefs about the defendant’s chance of conviction. Participants were informed that they were part of a jury for a court case in which a man has been accused of burglary and, depending on the condition, had or had not been detained pre-trial by a judge. This was crossed in a 2×2 design with ‘explanation’: the reason for pre-trial detainment was either not explained, or it was explained that this particular judge always makes the same detainment decision for this class of crimes. When the detainment was not explained, significantly higher conviction estimates were seen when the defendant was detained and participants’ explanations of their reasoning show a range of subtle and reasonable inferences. Initially, a smaller, but still significant difference in conviction estimates was still seen when the detainment decision was explained. However, participants’ explanations of their reasoning also showed a ‘confound’ where some participants thought the same pre-trial judge would be at the main trial, and may be biased against the defendant. Once these participants were removed from the analyses, no difference in conviction estimates was seen between detainment and no detainment in the ‘explained’ condition



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