DNA Evidence as the Basis for Conviction

The sufficiency of DNA evidence alone, with regard to convicting accused persons, has been interrogated and challenged in criminal cases. The availability of offender databases and the increasing sophistication of crime scene recovery of evidence have resulted in a new type of prosecution in which the State's case focuses on match statistics to explain the significance of a match between the accused's DNA profile and the crime-scene evidence. A number of such cases have raised critical jurisprudential questions about the proper role of probabilistic evidence, and the misapprehension of match statistics by courts. This article, with reference to selected cases from specific jurisdictions, investigates the issue of DNA evidence as the exclusive basis for conviction and important factors such as primary, secondary and tertiary transfer, contamination, cold hits and match probability which can influence the reliability of basing a conviction on DNA evidence alone, are discussed.