DNA Testing and Criminal Justice

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Advice on legislation or legal policy issues contained in this paper is provided for use in parliamentary debate and for related parliamentary purposes. This paper is not professional legal opinion.


Briefing Paper No. 05/2000 by Gareth Griffith


The purpose of this paper is to present an overview of the current debate in NSW about extending police powers to take forensic samples for DNA testing, a debate which has intensified over the past few months. The NSW Police Minister has foreshadowed the imminent introduction of relevant legislation. The paper’s main findings are as follows:
  • none of the participants in the local or wider debate on this issue have a blanket opposition to the use of DNA testing in criminal investigation. Instead, the discussion turns on questions of detail, concerning the scope of the proposed police powers and the nature of privacy/civil liberty safeguards which are to be established (page 1);
  • DNA profiling involves a probabilistic interpretation and, to assess the evidential value of a match, it is usual practice to estimate the probability that an unknown person, unrelated to the suspect, would share the same profile (page 3);
  • in relation to DNA profiles, population geneticists report that there are statistically significant ethnic differences. This raises the question of the need for subdatabases which distinguish between relevant racial/ethnic/cultural populations. The United Kingdom, for example, has three main databases for estimating match probabilities, composed of DNA profiles from people described as ‘Caucasian’, ‘Afro-Caribbean’ and ‘Indo-Pakistani’ (page 3);
  • in the United Kingdom the sampling process involves taking two mouth swab samples or, alternatively, a minimum of 10 hairs with roots (page 3);
  • the debate about extending police powers to use DNA samples for the purposes of criminal investigation has been on the agenda in Australia for around a decade, as part of a wider discussion concerning the reform of legislation dealing with forensic procedures. In February 2000, the Model Criminal Code Officers Committee released its final report titled, Model Forensic Procedures Bill and the Proposed National DNA Database (page 4);
  • a national DNA database is planned as part of the Commonwealth Government’s CrimTrac initiative (page 4);
  • the legal position in NSW is governed by section 353A of the Crimes Act 1900. Following the Fernando case, this amended in 1995 to permit samples of blood, saliva and hair to be taken from a person in lawful custody and upon a charge of committing an offence. These amendments were described at the time by the Attorney General as an ‘interim measure’ (pages 10-12);
  • following the release of the 1995 Model Forensics Bill a number of Australian jurisdictions introduced legislative amendments. The Commonwealth, Victoria and South Australia have introduced comprehensive legislative packages in this field, whereas the changes in Queensland have been more limited in nature. On the other hand, the reforms in the Northern Territory were not designed to reflect the terms of the 1995 Model Bill (page 14);
  • the Commonwealth, Victoria and South Australia permit the post-conviction testing of certain offenders. In Victoria, the law has a retrospective operation for any serving prisoner if found guilty of a ‘forensic sample offence’. Under the 2000 Model Bill retrospective testing will also be permitted in relation to ‘convicted serious offenders’, but under that proposal an offender can be in or out of prison (page 20 and page 25);
  • in the Northern Territory, mouth swabs (the standard technique used in DNA testing) are a ‘non-intimate’ forensic procedure and, unless the suspect is under 14, samples can be taken without the suspect’s consent and in the absence of a court order. Forensic procedures can be conducted upon those suspected of more serious offences in Victoria and South Australia, but there mouth swabs are intimate samples and, in the absence of the suspect’s informed consent, a magistrate’s order is required. Under the 2000 Model Bill, samples of hair with roots (the main alternative technique used in DNA testing) are non-intimate samples and can be taken compulsorily from adult persons in custody on the order of a police officer, as well as from convicted serious offenders (unless the offender is a child or an incapable person) (page 20 and page 23);
  • reference is often made in the current NSW debate to the impact DNA testing and matching has had on crime rates in the UK, in particular the impact it has had on crime clear-up rates. According to the NSW Police Commissioner, since the introduction of the national DNA database in the UK, in 1995, burglary was down by 40 per cent and the clear-up rate for unsolved crimes is up by 60 per cent (page 27);
  • in the UK both mouth swabs and hair samples (with roots) are defined to be non-intimate samples and they can be taken without consent from: a person in custody suspected of a recordable offence (broadly, offences which carry a sentence of imprisonment); any person charged with a recordable offence; any person convicted of a recordable offence (page 29); and
  • for the administration of justice generally, the issues at stake point in several directions – to the potential of DNA testing to free an innocent person who has been wrongly convicted, as well as to the question of the integrity of the DNA database and the need to safeguard against the tampering with, or faking of, evidence. The DNA testing debate also brings into sharp focus the role played by expert scientific evidence in the courts. It is almost certainly not a complete panacea for crime detection, nor yet an infallible evidentiary tool. It is, nonetheless, a remarkable and effective new instrument in the armoury of crime detection (page 32).