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

In R v McIntyre (2001), the defence argued that the DNA evidence was unreliable, as certain commercially sensitive
information about the Profiler Plus system was not publicly available, and so could not be properly discussed in
the scientific community. This argument was rejected. 1173 In that same year, in R v Gallagher (2001), DNA analysis
results adduced by the prosecution were questioned by the defence. The judge gave detailed reasons for admitting
the evidence, including a detailed explanation of the Profiler Plus system used by DAL to derive DNA profiles from
forensic material. 1174
Subsequent cases have also accepted the validity of the Profiler Plus system and the statistical basis on which the
evidence is given. For example, in R v Yates and others (2002), the accused argued on appeal that the statistical
model on which DNA evidence is given is flawed because it is based on a theoretical population, which breeds at
random, and does not in fact exist. The court found this submission had no substantial basis. 1175
Although the validity of DNA profiling is now widely accepted by the scientific and legal communities, laboratory
results may still be challenged. For example, in R v Ross (2003), the prosecution led evidence that police attended
the home of a 12 year old girl who reported she had been sexually assaulted, and put the child’s clothes in a plastic
shopping bag. The clothes were subsequently examined, and semen was detected on the underpants. The sample
was too small, however, to positively identify the source. At trial, the defence argued that by placing all the clothes
in the same bag, there was a possibility of cross contamination from one piece of clothing to another, or from the
shopping bag to the clothes. It was also argued that the material identified as semen could in fact have been wet
vegetable matter which had already been in the shopping bag. After being debated for several days on voir dire, this
evidence was eventually admitted. But the jury was unable to agree on a verdict, and a new trial was ordered. At the
retrial, the defence again sought to lead evidence about the possibility of cross contamination, but on this occasion
the court dismissed the argument as “fanciful.” 1176 The accused was ultimately acquitted.
Even though DNA analysis using the Profiler Plus system is now widely accepted, DNA analysis results may still be
open to interpretation, and so will continue to be challenged. For example, where there is only a partial match, and
there are results at fewer than the standard nine loci, the test is less discriminating. 1177
The Findlay review observed “a prevailing ignorance amongst many lawyers and judges about the nature and
potential of DNA evidence,” and argued that their reluctance to engage in the science has given the evidence “a
degree of legitimacy.” 1178 Indeed, none of the magistrates who responded to our survey had heard any proceedings
where the defendant challenged the interpretation of DNA evidence, or had heard any proceedings where the
defendant had the forensic material independently analysed. We also asked the DPP whether it was aware of any
matters where the defendant has challenged the interpretation of DNA evidence, or has contested the way the
forensic matching was carried out by DAL. The DPP advised that in R v MSK and MAK (2003), the unrepresented
accused challenged the admissibility of DNA evidence in a sexual assault matter, on the basis that DNA “could not
be distinguished between brothers from Pakistan as it may be able to with people from Western countries.” 1179 The
accused questioned several witnesses from DAL but the challenge was unsuccessful. In summing up, the judge
indicated it was not clear what was intended by the challenge, but it appeared to be an attack in some way on the
scientific integrity of the DNA testing. 1180
The DPP also advised that it is aware of some cases where the defendant has had the forensic material independently
analysed: “In a number of matters the defence have sought access to the laboratory file and after inspection of that
by a defence expert no challenge to the testing has occurred.” The DPP gave the example of R v Fricker (2003), where
the DNA was independently analysed, the accused pleaded guilty, and the DPP was not served with the results of the
independent testing. 1181
13.4.2. Challenges to the statistics
The probative value of DNA evidence comes from the high probability that DNA obtained from the crime scene or
victim has come from the accused. Defence lawyers may question the method used by the prosecution to arrive
at the figures it has. For example, in R v Styman and Tauber (2002), the prosecution gave evidence that duct tape
found in the accused’s ute had blood on it which came from the victim. The defence expert challenged the statistical
interpretation of DNA evidence, arguing the statistical probability of the DNA in question having come from the
accused was significantly lower than the probability claimed by the prosecution. The challenge was unsuccessful,
and the accused was convicted. He appealed but did not raise the issue on appeal. 1182
The “match probability” or “likelihood ratio” given in evidence is calculated using the product rule, where the likelihood
of finding a match at each of the loci examined are multiplied together. As one judge explained to a jury:
NSW Ombudsman
DNA sampling and other forensic procedures conducted on suspects and volunteers under the Crimes (Forensic Procedures) Act 2000 249