The effects of witness mental illness and use of special measures in court on individual mock juror decision-making

It is unclear whether witness mental illness and special measures used with witnesses in court impacts juror decision-making. Participants (N = 204) from the general public and student population completed a measure assessing attitudes towards mental illness before reading a mock trial vignette where witness mental illness (depression, schizophrenia, no mental illness) and the special measure used in court (screen, intermediary, no special measure) were manipulated. Participants were then instructed to formulate judgements about the witness testimony provided (reliability, competency, credibility) and their likelihood of finding the defendant guilty. The findings showed that witnesses with depression were perceived as significantly more competent than witnesses with schizophrenia, or with no mental illness. Witnesses with depression were also perceived as significantly more competent than witnesses with schizophrenia when a screen was used in court. There was however no difference in competency ratings for witnesses with depression versus those with schizophrenia when no special measure was used, or when an intermediary was used, although witnesses with depression were still viewed more favourably overall. These findings suggest that some awareness of these biases is needed in court. Improving clarity about why special measures are used in court might also go some way towards addressing this issue