Introduction

45.1 DNA evidence has become a powerful tool in exonerating persons wrongly convicted of criminal offences. Where DNA testing excludes the convicted offender as the source of a DNA sample found at the crime scene, sufficient doubt of guilt may be established to overturn the conviction. For example, in a sexual assault case involving one offender whose DNA sample is found on or in the body of the victim, DNA testing that excludes the person convicted of the offence as the source of the DNA would provide substantial doubt as to guilt. However, where the suspect admits that sexual contact took place, but claims that it was consensual, the presence or absence of DNA will be of little relevance.

45.2 As of 28 February 2003, 123 convicted offenders had been exonerated in the United States as a result of post-conviction DNA testing; a number of these had been on ‘death row’.^[1] The first Australian post-conviction exoneration occurred in April 2001, when a man’s conviction for rape was quashed after DNA testing conclusively eliminated him as the source of seminal fluid stains on the bed sheets found at the crime scene. The evidence had not been DNA tested before the trial.^[2]

45.3 DNA testing also can confirm guilt, removing doubt about a prisoner’s guilt despite long-running campaigns alleging a miscarriage of justice. For example, in May 2002, the English Court of Appeal held that DNA evidence proved beyond doubt that James Hanratty was guilty of the murder for which he had been hanged 40 years previously.^[3]