R v Humphrey

In the Supreme Court of South Australia, Bleby J considered the admissibility of DNA frequency evidence in the case of R v Humphrey. The accused was charged with the murder of Eugene Charles McLean, and the prosecution sought to rely on DNA evidence to link the accused to the crime scene. Ms Williams, a forensic scientist, provided a declaration stating that the accused was excluded as the source of blood stains found on his clothing, with a statistical likelihood of the profile being repeated in the general population being less than one in ten thousand. The defence challenged the admissibility of the frequency evidence, arguing that the data base used by Ms Williams was not representative of the relevant population and that there was a lack of dependency between the alleles. The court heard evidence from experts on both sides and ruled that the frequency evidence was admissible provided that evidence was also led from which the jury could determine the appropriateness or otherwise of the data base used. The court held that it was not for the trial judge to determine the appropriate population for the data base or to assess the representative nature of the sample within the data base. Instead, these matters were to be determined by the jury, properly directed. The court added a proviso that evidence should also be led from which the jury could determine the appropriateness or otherwise of the data bases used, to avoid the risk of the jury being overawed by the scientific garb in which the evidence was presented without an understanding of its foundation.