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

Chapter 12. Contamination issues
This chapter examines the measures in place to minimise and detect contamination, which is a very broad term, and
covers many different situations. Contamination may be deliberate or accidental, and the transfer of forensic material
may occur before, during or after the criminal incident being investigated occurs.
Concern about contamination is one of the most widely held concerns about the use of DNA analysis in the
investigation and prosecution of crime. As Justice Kirby has commented, effective procedures to minimise and detect
contamination are essential:
Given the likely devastating power of DNA evidence, it becomes doubly important to ensure the integrity of
collection of samples and their transmission, storage, testing, reportage and preservation for the scrutiny of
independent experts and, ultimately if need be, by the courts. 1091
The independent review of the Act on behalf of the Attorney General also foreshadowed the possibility that “with the
ever-greater reliance placed upon DNA evidence by the police and prosecution, comes the very real risk that evidence
of this kind may be fabricated or tampered with in order to meet burgeoning expectations.” 1092
12.1. Contamination prior to examination of the crime scene
Contamination of a crime scene prior to examination by law enforcement authorities can be deliberate or accidental.
12.1.1. Planting of evidence
Allegations of deliberate contamination of crime scenes by police officers are sometimes raised at trial. For example,
in a sexual assault matter, R v MSK and MAK (2003), the accused argued that police had planted a condom
containing his semen at the crime scene. He argued, “It is a fabricated condom, fabricated by police in order to make
their case strong.” The prosecution showed the video of the search of the crime scene to the jury and in summing up,
the judge commented that there was “not a crumb of evidence to suggest anything of the kind.” 1093
We are not aware, through our monitoring activities, of any instances of deliberate contamination of crime scenes.
However, some police officers expressed concern about DNA evidence being contested in court on the basis that
other offenders or unscrupulous investigators may have deliberately deposited DNA samples, such as cigarette butts,
hairs or bodily fluids at the crime scene. Others argued that this only emphasised the need for investigating police
officers to corroborate forensic evidence with other evidence. 1094
Concern about deliberate contamination of crime scenes has also been expressed by some judges. Justice Kirby has
commented that:
The planting of evidence (“giving of presents”) has been a distinct problem for the criminal justice system in the
past...[but] contamination or fabrication of evidence by officials is only part of the problem. The planting of false
trails by criminals, designed to implicate others as suspects, cannot be ignored. 1095
Justice Wood similarly commented that the possibility of DNA samples being used corruptly requires “vigilance on the
part of police services, forensic experts, prosecutors and defence lawyers alike.” 1096
There has also been some discussion about deliberate contamination of crime scenes by spraying a crime scene with
DNA which has been amplified using similar technology to that used by forensic laboratories. 1097
12.1.2. Adventitious or secondary transfer
Unlike deliberate contamination, the term ‘adventitious transfer’ (or secondary transfer) describes the transmission
of forensic material from a person who may not be associated with a crime, to the victim or crime scene, through
ordinary interactions. 1098 Everyone leaves behind tiny particles of DNA every day, just by breathing, talking, sneezing
and shedding skin and hair. DNA can be transferred through interactions as brief as brushing against another person
and leaving skin cells behind on that person. As forensic technology advances, and the sensitivity of DNA analysis
increases, DNA profiles can be obtained from much smaller traces of DNA. While this means that smaller quantities
of an offender’s DNA can be identified, it also means that a person entirely unrelated to a criminal incident may have
his or her DNA found at a crime scene, after having been present at the scene some time before the crime was
committed, or having been in contact with a person who subsequently came into contact with the victim or
crime scene.
NSW Ombudsman
DNA sampling and other forensic procedures conducted on suspects and volunteers under the Crimes (Forensic Procedures) Act 2000 231