Use of genetic information

Forensic DNA analysis

39.2 The forensic analysis of DNA usually involves comparisons between two bodily samples to determine the likelihood that they came from the same person. As discussed in Chapter 2, about 99.9% of the DNA molecule found within human cells is identical between any two persons. The remaining 0.1% is specific to the individual.[1]

39.3 Forensic analysis usually involves analysis of nuclear DNA, which is inherited from both parents in random combinations. DNA profiles are created from sections of non-coding DNA found within bodily samples such as blood, semen, hair, skin, urine, bone marrow and cells found in saliva, sweat and tears.[2]

39.4 Obviously, investigators will utilise any source available to obtain a DNA sample from a crime scene. However, obtaining samples directly from suspects (and convicted serious offenders) is regulated by Part 1D of the Crimes Act 1914 (Cth) (Crimes Act) and equivalent forensic procedures legislation in the States and Territories. In practice, police officers normally obtain a sample through the buccal swab method—which involves lightly scraping the inside of a person’s cheek with a swab to collect saliva and cells—or by taking hair samples (including the roots, since these contain the cells required for analysis) or blood samples (by a finger prick).

39.5 All Australian forensic laboratories regularly involved in criminal casework use a profiling kit known as Profiler Plus. This kit uses the polymerase chain reaction method, involving extraction of the DNA from the sample, amplification, and analysis to create the DNA profile. The profile comprises a set of numbers and an indicator of sex. A typical example of a DNA profile looks like this: ‘XY 10,12 18,19 14,14 15,16 25,28 16,12 11,10 29,30 17,18’. The numbers indicate the number of short tandem repeats (STRs)[3] found at nine sites, or loci, along the DNA molecule. There are two sets of numbers for each loci, one inherited from each parent.[4]

39.6 As a DNA profile represents only a small number of loci along the DNA molecule, it is possible that two persons who are not identical twins might coincid-entally have the same profile. However, the chance of such coincidence will decrease inversely as the number of loci examined increases. See Chapter 44 for more detail.

39.7 Mitochondrial DNA (mtDNA) is found outside the nucleus of a cell. It is less discriminating than nuclear DNA, but can be useful where a sample contains too little nuclear DNA for analysis.[5] By comparing polymorphisms on two persons’ mtDNA or on the Y chromosome, it is possible to identify relationships between a mother and her children, or between a father and son, respectively.[6] This can be useful in identifying human remains and in certain other investigations.

39.8 An emerging form of DNA analysis involves the identification of single nucleotide polymorphisms (SNPs) within the DNA molecule. SNPs represent alterations in DNA sequence of a single ‘letter’ in a person’s genetic code (eg A, C, T or G), and on average, base variations are observed every 1,000 bases throughout the genome.[7]

Uses for DNA analysis

39.9 DNA analysis is used as an intelligence tool to identify, confirm or eliminate a suspect in a criminal investigation. It may also be used to identify victims of crime or a mass disaster,[8] or to link crimes by comparing profiles created from DNA samples found at different crime scenes.

39.10 If a suspect’s DNA profile matches the DNA found at a crime scene, this match may be used as evidence pointing to the suspect’s guilt. However, a DNA match cannot be considered conclusive of guilt for a number of reasons, including the possibility that the match occurred by coincidence, as a result of error, contamination or tampering,[9] or that the suspect’s DNA was innocently left at the crime scene.

39.11 DNA profiling has also become a useful tool in exonerating convicted offenders.[10] Finally, DNA profiling could potentially be used as a form of unique personal identification—for example, in a DNA identity card.[11]

DNA and conventional fingerprints

39.12 Media and other accounts often suggest that DNA profiles are simply a modern form of fingerprint identification. In fact, DNA profiles differ from conventional fingerprints in several important respects. First, DNA holds vastly more information than fingerprints. A DNA profile can be used in establishing kinship relationships, and the sample from which the profile was obtained may hold predictive health and other information of a sensitive nature. Second, as genetic information is shared with biological relatives, an individual’s profile might indirectly implicate a relative in an offence. Third, while it can be difficult to obtain fingerprints of such quality as to be useful in an investigation, DNA can be amplified from tiny and aged samples, and may be recovered from almost any cell or tissue.[12]

Privacy concerns

39.13 It has been suggested that DNA sampling involves intrusion into three forms of individual privacy: bodily privacy, where the sample is taken from a person’s body; genetic privacy, where predictive health and other information about the person is obtained from the sample; and behavioural privacy, where the information is used to determine where a person has been and what they have done.[13] DNA sampling may also impinge on familial privacy where information obtained from one person’s sample provides information regarding his or her relatives.

39.14 In a submission to the Inquiry, the Office of the Victorian Privacy Commissioner discussed the balance between individual privacy rights and community safety in this context.

Privacy and respect for human dignity need not be abandoned when balancing civil liberties with community safety. In many ways, privacy principles will enhance the integrity and legitimacy of DNA profiling by limiting collection to the minimum necessary to achieve the legitimate aims of law enforcement agencies, requiring its use to be in accordance with these aims, demanding secure storage of DNA material, and requiring its destruction or de-identification when the information is no longer needed … Transparency and accountability reassure the community that what is sacrificed for greater safety and security is done so legitimately.[14]

[1] With the exception of identical twins. See D Kaye and G Sensabaugh Jr, ‘Reference Guide on DNA Evidence’ in Federal Judicial Center (ed), Reference Manual on Scientific Evidence (2000) Washington DC, 485, 491–492.

[2] Legislative Council Standing Committee on Law and Justice, Review of the Crimes (Forensic Procedures) Act 2000, Report No 18 (2002), Parliament of NSW, Sydney [2.11], quoting the evidence of Linzi Wilson-Wilde.

[3] A short tandem repeat is a locus along the DNA molecule that is composed of a short sequence of between two and seven bases of DNA, which is repeated a number of times in a particular region of DNA.

[4] J Gans and G Urbas, ‘DNA Identification in the Criminal Justice System’ (2002) 226 Australian Institute of Criminology: Trends & Issues 1, 2. The Inquiry understands that in some circumstances a number may appear in a DNA profile as an ‘NR’ (ie not recordable), or may be followed by a ‘V’ (ie variant): CrimTrac, Consultation, Canberra, 23 August 2001.

[5] Legislative Council Standing Committee on Law and Justice, Review of the Crimes (Forensic Procedures) Act 2000, Report No 18 (2002), Parliament of NSW, Sydney [2.4].

[6] See Ch 36 for more detail.

[7] See Ch 2 for more detail.

[8] See Ch 42 for more detail.

[9] Legislative Council Standing Committee on Law and Justice, Review of the Crimes (Forensic Procedures) Act 2000, Report No 18 (2002), Parliament of NSW, Sydney [3.22].

[10] See Ch 45 for more detail.

[11] For example, a ‘genotype ID card’ has been developed by Zhongnan (Central-South) Hospital Gene Diagnostic Center under Wuhan University in China. The card contains a genetic profile representing 18 loci along the DNA molecule: China’s First Genotype ID Card Comes Out in Wuhan, People’s Daily Online, <>, 20 June 2002.

[12] See the discussion in Human Genetics Commission, Inside Information: Balancing Interests in the Use of Personal Genetic Data (2002), London, 145.

[13] J Gans, Submission to the Victorian Parliament Law Reform Committee’s Inquiry into Forensic Sampling and the Use of DNA Databases in Criminal Investigations (2002), 2.

[14] Office of the Victorian Privacy Commissioner, Submission G171, 8 August 2002.