Decision analysis in forensic science

Forensic scientists are routinely faced with the problems of making decisions under circumstances of uncertainty (i.e., to perform or not perform a test). A decision making model in forensic science is proposed, illustrated with an example from the field of forensic genetics. The approach incorporates available evidence and associated uncertainties with the assessment of utilities (or desirability of the consequences). The paper examines a general example for which identification will be made of the decision maker, the possible actions, the uncertain states of nature, the possible source of evidence and the kind of utility assessments required. It is argued that a formal approach can help to clarify the decision process and give a coherent means of combining elements to reach a decision.     

Sexual and nonsexual offenders with intellectual and learning disabilities: a comparison of characteristics, referral patterns, and outcome

This article reports an evaluation of a community intellectual disability offender service over the period from 1990 to 2001. Men who committed sex offenses or sexually abusive incidents (n = 106) and men who committed other types of offenses and serious incidents (n = 78) are compared on personal characteristics, referral sources, forensic details, and outcome up to 7 years after referral. The cohorts are older than one would expect from the criminology literature, and, at about 33%, the incidence of mental illness is consistent with some previous studies. A greater proportion of sex offenders had criminal justice involvement and a formal disposal from court. Fire raising was not overly represented as an offense. There was a higher rate of reoffending in the nonsexual cohort, which persisted up to 7 years. Investigating only reoffenders, there was a considerable amount of harm reduction recorded up to 7 years, statistically significant up to 5 years following initial referral.     

Lineup Identification by Children: Effects of Clothing Bias

This study examined effects of clothing cues on children's identification accuracy from lineups. Four- to 14-year-olds (n = 228) saw 12 video clips of individuals, each wearing a distinctly colored shirt. After watching each clip children were presented with a target-present or target-absent photo lineup. Three clothing conditions were included. In 2 conditions all lineup members wore the same colored shirt; in the third, biased condition, the shirt color of only one individual matched that seen in the preceding clip (the target in target-present trials and the replacement in target-absent trials). Correct identifications of the target in target-present trials were most frequent in the biased condition, whereas in target-absent trials the biased condition led to more false identifications of the target replacement. Older children were more accurate than younger children, both in choosing the target from target-present lineups and rejecting target-absent lineups. These findings suggest that a simple clothing cue such as shirt color can have a significant impact on children's lineup identification accuracy.