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

1.4.2. What is a DNA profile
The areas of DNA that are non-coding have been labelled ‘junk’ DNA. DNA profiles consist of a list of the variations
obtained from certain sites (called loci) on the junk DNA plus the sex gene (XX for female, XY for male). The areas
on the junk DNA that are examined are called Short Tandem Repeats (STRs). These are small sections of DNA that
are repeated end on end. Different people have a different number of repeats, and therefore have different lengths of
DNA. Analysing and measuring the different lengths of DNA at these sites is the basis of DNA profiling. 12
DNA laboratories in all Australian jurisdictions use the ‘Profiler Plus’ system of DNA profiling. 13 Forensic scientists do
not examine the whole DNA, but only a certain number of loci on the DNA. The more loci examined the greater the
likelihood that samples with the same profile came from the same person. In New South Wales, the DNA laboratory
examines nine loci.
A DNA profile is different from a DNA sample. A sample contains the whole of a person’s DNA, while a profile is a
series of numbers and letters derived from only a small portion of a person’s DNA. A DNA sample contains a great
deal of information about a person, including predictive health information. While some genetic information can be
derived from a DNA profile, including the person’s sex and whether he or she may be related to another person
whose profile is known, a profile contains far less genetic information than a DNA sample.
1.4.3. How is DNA used in criminal investigations
DNA from biological material found at a crime scene can be compared with the DNA police take directly from a
person, to determine whether the biological material found at the crime scene is likely to have come from that person.
If police suspect that a person has committed a particular offence, they can take a DNA sample from the person,
and send it to the laboratory for comparison with DNA obtained from the crime scene. DNA profiles are extracted
from both the person and crime samples. If the profiles match, this may be evidence, in some circumstances, that
the person was involved in the crime. Further, the person’s profile will be put on the DNA database, and may link the
offender to other unsolved crime scenes.
Police may send forensic material from crime scenes to the laboratory for analysis even where they have not been
able to identify a suspect, as it may match a profile on the DNA database from another crime scene, or a suspect or
convicted offender whose profile has already been put on the database.
DNA evidence has been used as a tool in many high profile criminal investigations, including the Ivan Milat
backpacker murder cases, the investigation of the attempted extortion of Arnotts Biscuits and the investigation into
the disappearance of English backpacker, Peter Falconio.
Because DNA is very stable, and can withstand significant environmental impact, DNA profiles can be developed
from biological material which is decades old. For this reason the new technology has also enabled police to reopen
investigations of old unsolved crimes.
DNA is not only helpful to convict offenders; it can also be used to exclude suspects from police investigations. This
can prevent unnecessary investigation and save valuable police resources.
Development of DNA technology has also meant that people can appeal against older convictions, if they can show
that DNA taken from the perpetrator at the time of the offence does not match their own DNA.
DNA technology has also been used for identifying disaster victims, including those killed in the 2002 Bali bombings
and the 2004 tsunami in south east Asia.
1.4.4. The DNA database
The DNA database is used for identifying links between offenders and crime scenes. It is primarily an intelligence tool.
If a link is established between a person and a particular crime scene, this does not mean the person is guilty – it
simply means that police have further information which they may be able to use to progress their investigation.
Over 25,000 person samples have been loaded onto the New South Wales DNA database, including about 19,000
samples from convicted offenders, 8,000 from suspects and 800 from volunteers. Over 14,000 crime scene samples
have been loaded onto the database. 14
It is not possible to say exactly how many people have their DNA on the database, as the Act prohibits profiles taken
from suspects to be compared against samples taken from suspects which are already on the database. 15 This
NSW Ombudsman
DNA sampling and other forensic procedures conducted on suspects and volunteers under the Crimes (Forensic Procedures) Act 2000 3