The recent High Court decision in Aytugrul v The Queen  HCA 15 raised an interesting question as to whether the manner in which statistical expert DNA evidence is presented can have such a prejudicial or misleading effect so as to render it inadmissible.
The accused was being tried for murder. A hair found under the deceased’s thumbnail underwent DNA testing. Expert evidence of the testing was given at trial which included a finding that “99.9 per cent of the population could not have [the same DNA profile as the accused]”.
The accused was found guilty and appealed on the basis that, among other things, the above evidence should have been found inadmissible under section 135/137 of the Evidence Act, its prejudicial effect or tendency to mislead or confuse outweighing its probative value.
In the NSW Court of Criminal Appeal (CCA) McClellan CJ dissenting said the evidence raised questions of “intelligibility” and “juror comprehension”.
There was no expert psychological evidence dealing with these kinds of matters before the Court, but His Honour made reference to a number of published articles and appeared satisfied that they were sufficient to warrant a finding that the evidence should be rejected.
Even though unsuccessful on appeal to the CCA, perhaps buoyed by the Chief Judge’s dissenting opinion, the accused appealed to the High Court.
The plurality in the High Court found that in the absence of these kinds of matters being taken on judicial notice by the court, for which there was no proper basis, there was no sufficient reason for refusing to admit the opinion into evidence.
It begs the question as to what might have happened if the defendant had led expert evidence of the psychological effect statistics can have on people (jurors) if presented it a certain way.
Given the increasing prevalence of DNA evidence in criminal trials it may not be too long until the question is looked at again and an expert is called to opine on the kinds of matters by which the NSW Chief Judge at Common Law was persuaded.