Crimes (Forensic Procedures) Act 2000 - NSW Ombudsman - NSW ...

A challenge of this nature was successful in a recent West Australian case, R v Bropho (2004). The complainant,
who had a mental illness and experienced delusions, alleged that the accused had raped her 23 years before. The
prosecution calculated the likelihood of the accused being the father of a child born at the time to be 3,134 times
more likely than a random person being the father. However, the defence argued that a different value should be used
to compensate for underlying interrelatedness in the relevant population, which gave a likelihood of only 358 times
more likely. The judge found there were no reliable studies of the genetics of the particular population, and so could
not determine what the appropriate value would be to compensate for underlying relatedness. In addition, the offence
occurred a long time before, close relatives of the accused could not be excluded, and the complainant was not a
reliable witness. There was reasonable doubt as to the accused’s guilt, and he was acquitted. 1194
13.4.3. Challenges based on the way the evidence is presented
Even where the DNA evidence is accepted as statistically valid, the defence may challenge the way that evidence
is presented to the jury. The general position now is that DNA evidence can be put before the jury, provided it is
accompanied by appropriate directions. Previously, however, conflicting DNA evidence had been excluded on the
basis that it was inherently confusing and could mislead the jury. In R v Lisoff (1999), the accused was charged with
assault causing grievous bodily harm. The prosecution sought to adduce evidence that the victim’s blood had been
found on tracksuit pants the accused was wearing at the time of the assault. The defence submitted that the blood in
question was actually “post transfusion blood,” and argued that police had planted it to implicate the accused after
the victim had received a blood transfusion, following the assault. The trial judge excluded the evidence, on the basis
that there was a real danger the jury would be unduly swayed by the scientific nature of the evidence. The prosecution
appealed against the decision to exclude the DNA evidence. The appeal court found that the evidence should have
been admitted, and that the dispute between the experts should have been left to the jury to determine:
There is nothing so extraordinary about the conflict in the evidence presented in this case which would justify
the conclusion that a careful and sensible jury, properly directed as to the relevant law and as to the relevant
evidence, could not decide in a reasoned and responsible way whether or not the Crown had demonstrated
beyond reasonable doubt that the body of evidence supporting the Crown case should be preferred to the
opposed body of evidence... The essential questions for the jury, if properly formulated and explained by
reference to the available evidence, were in our opinion no more essentially complex or difficult than questions
of fact that are routinely, and correctly, left to juries in criminal cases. 1195
The court ordered a retrial, and the accused was ultimately acquitted.
In the following years, the courts considered whether the statistics relating to DNA analysis, which is essentially
opinion evidence, should be put before the jury. In R v GK (2001), the accused was charged with sexually assaulting
his stepdaughter, and the prosecution led evidence that he was the father of the complainant’s baby. The trial judge
admitted evidence that DNA testing did not exclude the possibility of paternity, but ruled that “there should not be
arithmetical figures put before the jury,” on the basis that the probative value of the evidence was outweighed by the
danger of unfair prejudice to the accused. The accused was acquitted, and the DPP submitted a question of law to
the Court of Criminal Appeal, asking whether the trial judge erred in refusing to admit the statistical evidence. The
Court of Criminal Appeal held that the statistical evidence should have been admitted. Although courts may have
legitimate concerns about whether DNA evidence is capable of being understood by a jury, these can be addressed
through careful directions and warnings to the jury:
There is, at least as a general rule, nothing so inherently difficult, confusing or misleading about properly
qualified expert opinion evidence about DNA testing, either in general or in a particular case, as would justify a
perception that a jury, acting reasonably and with the assistance of correct and appropriate directions from the
presiding Judge, cannot be entrusted safely with the assessment of that opinion evidence. 1196
Further, the fact that DNA evidence may be overwhelmingly probative does not of itself create a danger of unfair
prejudice:
Merely because evidence points overwhelmingly to guilt does not make it unfair to adduce it. And even if
evidence carries a prejudicial overlay its genuine probative value must be put in the scales... If relevant DNA
statistical evidence is tendered through a witness of due expertise then its probative weight cannot itself be a
ground for withholding it from the jury. 1197
The court also noted the general move towards admissibility of statistical calculations relating to DNA analysis in
other jurisdictions.
NSW Ombudsman
DNA sampling and other forensic procedures conducted on suspects and volunteers under the Crimes (Forensic Procedures) Act 2000 251