Introduction: This study aims to assess how forensic deoxyribonucleic acid (DNA) evidence assists decision-makers in sexual offence cases, in decisions to prosecute, decisions to plead guilty and how it assists juries and judges in decisions of guilt or innocence. Its association with custodial penalties is also examined. The primary method relied on was an archival study of case records. This involved comparing the characteristics of criminal case records from two different categories, those that were referred to the forensic laboratory, and for which a scientist provided a sworn court statement that associated the defendant with either the complainant or the crime scene, and similar cases for which no DNA evidence was presented in court. The differences that DNA evidence made, if any, were then assessed by comparing the characteristics of the DNA group cases to the control group at the various decision-making stages, while allowing for the other evidentiary and extra-legal factors that influenced case outcomes.