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

that he had buried her beneath the house. The victim’s parents provided DNA samples for comparison with bone
fragments found under the house. The prosecution expert stated that “it is approximately 660,000 times more likely to
obtain this particular DNA profile found in the bones if it comes from a child of [the victim’s parents] than from a child
of a random mating in the Australian population.” However, the trial judge went further than this, telling the jury that,
according to the prosecution, “there is a 660,000 to one chance that those are the bones of [the victim] as distinct
from any other person.” The court found that “if it was proper to leave the jury with odds at all, the jury was left with the
potentially misleading odds of 660,000:1 and without guidance on what the DNA statistical evidence really meant.”
The court could not conclude that the accused would inevitably have been convicted, had the jury not been left with
an erroneous appreciation of the statistical evidence adduced at trial. The appeal was allowed, and a new trial was
ordered. 1206
DNA evidence has also been challenged where analogies have been drawn to fingerprinting. In R v Yates and others
(2002), counsel for the defence argued that referring to a DNA profile as “DNA fingerprinting” tended to give it a
significance which it did not have. The court commented that while it is highly desirable for judges to avoid this term,
it was not misleading in that case, as the judge had given appropriate directions. 1207 The issue was also raised in
R v Wakefield (2004). On appeal, the defence argued that use of the term “DNA fingerprint” was inaccurate and
misleading. However, the prosecution expert had actually commented, “I would prefer the term genetic profile rather
than fingerprint. I think fingerprint has got a connotation of uniqueness and we’re not talking about uniqueness here,”
and counsel for the prosecution had referred to the DNA profile as being “like a fingerprint.” The court commented
that “when explaining DNA profiles the analogy of a fingerprint is not apt and should not be used,” but dismissed the
appeal, as the evidence had been properly explained during the trial. 1208
13.4.4. Continuity of evidence and possibility of contamination
DNA evidence may also be challenged on the basis that it may have been contaminated or otherwise damaged. For
this reason, the prosecution must be able to show that the relevant samples were handled appropriately, including
being stored securely in appropriate conditions, throughout the relevant period.
In the Northern Territory case R v Murdoch (2005), the accused was charged with the murder of British backpacker
Peter Falconio. The defence challenged the DNA evidence on the basis that it may have been contaminated. First,
there was evidence that investigating police had taken the cable ties used to bind the hands of the victim’s girlfriend
to a meeting with the accused in an Adelaide prison, in 2002. Witnesses for the prosecution denied that the accused’s
DNA could have come into contact with the ties at that time, stating that the ties remained in a paper bag on a table
in the room throughout the meeting. 1209 Second, the defence questioned whether the evidence could have been
contaminated before being sent to the United Kingdom for analysis. The original examination of the items, in Australia,
was inconclusive, and the evidence was sent overseas for examination by a laboratory which uses a more sensitive
method of testing (called low copy number, where a DNA profile can be derived from a very small number of cells).
The British forensic scientist gave evidence that DNA found inside the cable ties and on the gearstick of the victim’s
car matched the DNA of the accused. An expert for the defence questioned this evidence, arguing that because the
system used is so sensitive, it could have picked the DNA up from somewhere else, for example at the crime scene,
during transit or at the laboratory. The accused was ultimately convicted. 1210
Inability to account for the movement of crime scene exhibits may be a problem for older offences. For example,
a man was charged in the United States after his DNA linked him to a 1979 murder. While there was no evidence
that the crime scene evidence had been contaminated, there were conflicting records about where it had been
kept for several years following the murder. The prosecution decided not to proceed, as it could not account for the
whereabouts of swabs taken from the victim during that period. 1211
Some of the police officers we consulted predicted that, given how discriminating DNA analysis is, challenges relating
to continuity of evidence and the possibility of contamination will be made more frequently:
Greater scrutiny will be placed on crime scene management and interpretation of that evidence in court. 1212
Because it is near impossible to prove that the DNA does not belong to the criminal, it is envisaged that defence
solicitors will raise issues of cross contamination, corrupt placing of DNA, strict compliance with police policy
and procedures, continuity of the sample. 1213
At the moment continuity and integrity of testing procedures are the main issues challenged at trial. This will
continue to be a problem... If they can’t dismiss the identification, defence will try to have the evidence excluded
due to contamination or failure in testing. 1214
NSW Ombudsman
DNA sampling and other forensic procedures conducted on suspects and volunteers under the Crimes (Forensic Procedures) Act 2000 253