The role of personal mitigating factors in criminal sentencing judgments: an empirical investigation

Criminal sentencers must weight and integrate many different factors to reach a judgment, including aggravating factors that argue for a harsher sentence, and mitigating factors that suggest a more lenient sentence. Personal Mitigating Factors (PMFs) relate to the offender, rather than the offence (e.g., remorse or youth/immaturity). Research shows that discretionary sentencing produces inconsistency and bias and lacks the transparency needed to maintain public trust in justice. Although many jurisdictions have introduced more structured sentencing, the mitigation process remains largely discretionary. Structuring personal mitigation could help produce fairer sentences. Any structured approach must, however, be informed by empirical data, and little is known about how sentencers use PMFs, or how the public judges them. This thesis examined the role of three commonly occurring PMFs: remorse, good character, and addressing addiction.
Study 1 examined sentencers’ use of PMFs in cases of assault and burglary through a statistical analysis of annual sentencing data from the Crown Court in England and Wales. Study 2 used a qualitative analysis of interviews with a small sample of Crown Court judges to further explore the findings of Study 1 and identify topics for future research. Studies 3 and 4 used experimental designs to measure how the three PMFs influenced public judgments about sentencing fairness and choice of sentence length. Study 4’s “idiographic” design permitted evaluation of the variation between individuals’ judgments about PMFs.
The present thesis identified several issues with current sentencing practice, notably the underweighting of multiple co-occurring PMFs, and proposed some practical options for structuring the personal mitigation process. The thesis also identified conflicts between sentencers’ use of PMFs and public judgments, and suggested how the gap between sentencers and the public could be closed. Lastly, the thesis illustrates how methodology from psychology can be used to advance our understanding of criminal sentencing.