International research has suggested that rapist criminal histories can be predicted from certain offence behaviours. Ninety-six solved stranger rape cases were examined to determine if there was consistency in a New Zealand sample. Rapist behaviours during the offence were compared with criminal convictions prior to the rape. The primary statistical technique used was likelihood ratio stepwise binary logistic regression. Predictive utility of the results was limited, due to significant correlation coefficients between the criminal history variables. Nevertheless, the current study reflected the general findings of similar descriptive international research. These outcomes were: the majority of stranger rapists had prior criminal convictions, and the majority of those convictions were for property offences not sexual offending. Furthermore, ethnic minorities were over-represented among the offenders, and the majority of stranger rapists started committing their first known rapes in their midto late 20s. Finally, methodological difficulties were encountered during this study. This highlights the need to refine existing statistical approaches to predictive offender-based research.

Spermatozoa and prostatic acid phosphatase, identified in vaginal fluid after an alleged sexual assault, constitute important physical evidence useful in courts of law during rape trials. It has been recommended that the physician examining a victim of alleged sexual assault should promptly attempt identification of spermatozoa in a native preparation of vaginal fluid. Additionally, he should collect certain specimens that later can be evaluated in detail in a forensic pathology laboratory. The presence or absence of spermatozoa, prostatic acid phosphatase, and various blood group substances can be ascertained with a variety of laboratory methods. This study was undertaken to investigate the following items: (1) the correlation of spermatozoa detected in native preparations of vaginal fluid and of results obtained by various forensic laboratory methods; (2) the incidence of detection of seminal fluid constituents at certain time intervals following an alleged rape; and (3) the possibility that acid phosphatase detection provides additional evidence when spermatozoa cannot be identified in native or fixed preparations of vaginal fluid.