Judging defendants with learning disabilities: expert witness testimony, defendant appearance, and perceptions of offenders with ld in the criminal justice system.

Powell, Georgia M. (2025) Judging defendants with learning disabilities: expert witness testimony, defendant appearance, and perceptions of offenders with ld in the criminal justice system. Doctoral thesis, University of East Anglia.

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Abstract

Background: The diagnosis of a learning disability (LD) is suggested to have particularly stigmatising connotations, particularly within the criminal justice system (CJS). There is limited research however on how psychological information presented in a criminal trial, together with the defendant’s physical appearance, may impact upon juror ratings of guilt and perceptions of expert witness credibility.

Method: The systematic review sought to synthesise qualitative studies investigating the attitudes of CJS professionals to people with LD (PWLD), specifically offenders with LD, and to appraise their methodological quality. The empirical paper built upon the findings of previous research by exploring the impact of a defendant’s facial visible physical difference suggestive of LD and the content of expert witness testimony on jurors’ perceptions of expert witness credibility and juror decision making when the defendant's mental health is considered in the courtroom.

Results: Ten papers were included in the systematic review, spanning 766 participants. Methodological quality was broadly of a high standard. Five themes were identified: Conflating Diagnoses, Perceptions of PWLD as Offenders, Procedural Issues Affecting PWLD, Development and Maintenance of Perceptions, and Impact of Training. The empirical study found no statistically significant main or interaction effects of either presentation of expert witness testimony information or defendant’s appearance on jurors' perceptions of the defendant’s guilt or the expert witness’ credibility.

Conclusions: This study highlights the need for further research into expert witness credibility and juror decision making to better understand jurors’ unconscious biases and cognitive processes. Strengths, limitations, and implications for future research and practice are discussed.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User:	Nicola Veasy
Date Deposited:	27 Oct 2025 15:07
Last Modified:	27 Oct 2025 15:07
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100794
DOI:

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