DNA Matching for criminal identification purposes

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The BCCLA recognizes and supports the aim of amending the Criminal Code and the Identification of Criminals Act to allow law enforcement authorities to obtain a warrant to collect DNA samples from suspects in serious crimes, to demand DNA from those arrested for serious crimes, and to bank DNA information for legitimate law enforcement purposes.

Framing policies and procedures to institute these practices and to identify their limits is a matter of some urgency, both because of the potential value of DNA printing as a law enforcement tool and because of the civil liberties issues that these practices raise. This brief is an attempt to put these issues in perspective and to make recommendations for policy that will put law enforcement and civil liberties interests in balance.


DNA matching is being hailed as the greatest advance in criminal investigation techniques since the advent of fingerprinting. According to generally accepted and widely confirmed genetic theory, a person’s DNA print is, with one exception, always unique to that person (the only exception being cases of identical twins). DNA is present in almost every cell in the body, and a DNA print is readily obtainable from various bodily tissue and fluids (hereafter called tissue), such as blood, hair, skin, saliva and semen.

If any of this tissue is found at a crime scene, the police can have the sample analyzed at a laboratory, and a DNA print obtained. It then becomes a question of whose DNA print was found at the crime scene. If the police have a suspect, and if they can obtain a bodily sample from the suspect, they can determine with a high degree of accuracy whether the sample at the crime scene contains the same DNA print as the sample taken from the suspect. If there is no match, the suspect can very often be ruled out as the perpetrator, whereas if there is a match, the evidence against the suspect can often be compelling. DNA prints obtained from crime scenes can also be matched against DNA prints collected by the police and maintained in a data bank; and a DNA print taken from tissue from the suspect or the suspect’s home or car can be matched against DNA taken from the crime scene or from the victim. It is clear that DNA matching is a powerful criminal investigation tool.

DNA samples are now most frequently analyzed in North America by a technique called restriction fragment length polymorphism (RFLP). For each sample, a DNA sequence from the same chromosomal region is cut, and a stain or picture of it is produced, which is called an autoradiograph. Autoradiographs look like bar codes. These are visually compared to discover if the patterns of DNA are identical. This process is typically repeated four other times for different chromosomal regions of the DNA molecule. If the DNA patterns for each of the five chromosomal regions are identical, a match has been found. The confidence that the two samples have been correctly matched (that they came from the same person) depends on the quality of the samples and the stringency with which the tests were applied. If there is a discrepancy in any of the five samples, the tissue samples did not come from the same person.

RFLP analysis does not identify genetic traits, such as gender, hair or eye colour, or predisposition to certain diseases. The chromosomal regions selected for RFLP analysis are junk DNA, that is, DNA that has not been linked to any specific genetic traits, and so which have no descriptive or diagnostic value. Junk chromosomal regions are selected for analysis because they contain a high degree of genetic variability among persons of particular racial population groups. They are therefore especially useful for identifying whether different samples of DNA come from the same person. It is possible that junk DNA may one day have diagnostic and descriptive uses, but that does not appear likely for the near future. Other methods of analysis besides RFLP are also being developed and may eventually replace this method. As far as we can tell, however, the potential for abuse that could arise with these methods and by developments in genetic screening would be addressed by the recommendations we advance below.

There are three ways in which DNA information could be stored. The first is to store the tissue sample itself. The second is to store the autoradiographs. The third is to translate the information on the autoradiographs to a numeric or alpha-numeric code. The first two methods are currently used, and the third (if it has not been used already) could be easily utilized. It would allow easy computer storage and transmission of the information, and a quick method of screening for a match.

A number of people in Canada have called for changes to the Criminal Code and the Identification of Criminals Actthat would allow police to demand DNA samples from suspects and to bank DNA information much like fingerprint records are kept. The people who have joined this call include the police, judges, prosecutors, victims groups and the defence bar. According to B.C. Supreme Court Judge Thomas Melnick:

In my view, the need for a warrant procedure for such searches is clearly not only desirable but necessary, given the present state of investigative techniques with respect to DNA analysis. The police should have the availability, and detainees the protection, of the warrant procedure for such seizures” (R. v. Williams (1992), 76 C.C.C. (3d), p .410).

Defence lawyer Russ Chamberlain has said that he would favour a system in which a judge, on reasonable and probable grounds, could issue a warrant to obtain a DNA sample: We should all be concerned about getting reliable and truthful evidence before the court (Vancouver Sun, March 3, 1994).

In addition to warrants for DNA samples, it has been suggested that the Identification of Criminals Act be amended so that a DNA data bank could be created. One suggestion is that this data bank contain the DNA prints of all known or convicted sex offenders. Another suggestion is that the data bank contain the DNA prints of all violent criminals.


  1. The Status Quo

    There is currently no statutory authority for police to demand a tissue sample for DNA matching from anyone, with or without a warrant. The police have had to work around their inability to demand or obtain a warrant for a DNA sample by trying to get consent, and by collecting samples from discarded bodily tissue or fluids, such as semen, blood, saliva and hair. A recent example reported to the BCCLA: police learned that an inmate suspected of committing a sexual assault had a dentist appointment. They obtained a search warrant to conduct blood typing, and after the inmate’s appointment seized the swabs used in the dental procedure. They then conducted both blood typing and DNA tests on the discarded bodily fluids. Police have also been reported to have searched a suspect’s hat or brush for hair samples, to have examined bed sheets for fluid stains, and to have retrieved a bandage in the hope of recovering blood. (Vancouver Sun, March 3, 1994)

    i. The Principled Issues

    (a) The Charter

    Section 8 of the Canadian Charter of Rights and Freedoms protects persons against unreasonable search and seizure, and has been interpreted to provide constitutional protection for privacy. It protects a biographical core of personal information which persons in a free and democratic society would wish to control from dissemination to the state. In interpreting section 8, the courts must make an assessment whether in the particular situation the public’s interest in being left alone must give way to the state’s interest in intruding on the individual’s privacy in order to advance its goals, notably law enforcement.

    In Hunter v. Southam Inc. (1984) the Supreme Court of Canada ruled that the purpose of section 8 requires a means of preventing unreasonable searches before they happen, not simply of determining after the fact that they ought not to have occurred. This can only be accomplished by a system of prior authorization. Where the individual has a reasonable expectation of privacy, prior authorization is a precondition for a valid search or seizure. The standard which must be met before a search should be authorized is the establishment upon oath of reasonable and probable grounds to believe that an offence has been committed, and that there is evidence to be found at the place of the search.

    Under section 1, where a search or seizure would be unreasonable, it could still be permitted where it was demonstrably necessary in a free and democratic society.

    Under section 24(2), even where there has been an unreasonable search or seizure, the evidence obtained could still be admitted in a court of law so long as doing so would not, having regard to all the circumstances, bring the administration of justice into disrepute.

    (b) Statutes

    A person’s fingerprints and DNA information are considered to be personal information for the purposes of the federal Privacy Act and the provincial Freedom of Information and Protection of Privacy Act.

    (c) Factors Determining the Extent of Privacy Violation

    There are three factors which determine the seriousness of an invasion of privacy. The first is whether the person has a reasonable expectation that the information is private, and will be accessible by others only with the person’s consent. The greater the expectation of privacy, the greater the invasion. Reading someone else’s mail without their consent is more invasive than reading their shopping list on the refrigerator door.

    The second is how sensitive the information is, that is, what the impact on them might be from non-consensual disclosure. Reading someone’s diary, or their medical test results, would normally be more invasive than reading their hydro bill.

    The third is how invasive the method of obtaining the information is. A rectal search is more invasive than a pat frisk, and searching someone’s home is more invasive than a perimeter search.

  2. The Case for DNA Testing

    The police claim that with the power to obtain DNA samples their ability to solve crimes where the identity of the perpetrator is in question would be significantly improved, particularly in violent crimes and sexual assaults since human tissue is often left at the scene of such crimes. A survey conducted by the RCMP’s serious crime unit in B.C. revealed that:

    • There were 69 serious investigations in which DNA evidence was recovered at the crime scene.
    • Investigations in which DNA could have been a deciding factor included 45 unsolved murders, three attempted murders, 20 sexual assaults and one aggravated assault.
    • In 23 of the investigations, key suspects refused to give biological samples for DNA testing.
    • In 20 of the cases, no other evidence, apart from DNA samples recovered at the crime scene, is known to exist.
    • Police fear that suspects in 16 of the investigations, including two rape cases, remain criminally active.
    • Six suspects were eliminated through DNA analysis.

    The police argue that, although the privacy rights of citizens must be protected, these rights do not include the right of a guilty person to escape prosecution unless a compelling reason can be offered. It is in everyone’s interest (except the perpetrator’s) that those guilty of crimes, especially violent crimes and sexual assaults, are prosecuted and the innocent are not wrongly charged or convicted. Giving the police the power to compel the production of DNA samples, or to apply for a warrant to do so, would significantly enhance their ability to further these interests.

    Taking of a DNA sample is not an unacceptably serious invasion of a person’s body. We already allow the police to demand a breath or blood sample where the person is suspected of impaired driving, and we allow rectal examinations with a warrant. Taking a swab from a person’s mouth or plucking a strand of hair is no more intrusive than taking a breath or blood sample, and is much less intrusive than a rectal examination.

Analysis and general recommendations

  1. The General Position

    The BCCLA supports giving authority to the police to obtain DNA samples from suspects for identification purposes in certain circumstances where it would aid in the investigation of indictable offenses. We are generally persuaded by the arguments advanced in the previous paragraphs. The public interest which is served is great, especially in cases of violent crime where DNA matching is likely to prove most useful. The invasiveness of the methods of obtaining DNA samples (plucking a few strands of hair, rubbing a swab around the person’s mouth, or obtaining a drop or two of blood from a pin-prick to a finger), while not insignificant, is nevertheless relatively slight compared, for example, to rectal or strip searches which are accepted practices in our criminal justice system.

    The privacy issues surrounding the use (and abuse) of DNA information are more compelling. But although individuals have a more powerful expectation of privacy regarding their DNA information, and although the effect on the individual from police possession of this information could be great, the BCCLA judges that there exist many circumstances in which the public interest in prosecuting persons guilty of serious crimes outweighs these interests.

    This position depends on our understanding that the bodily tissues from which the DNA prints are obtained from suspects would be destroyed as soon as the prints are obtained. Identifying the perpetrators of violent or sexual crimes is the only justification for allowing the police to demand DNA samples from individuals, and this interest is completely satisfied when the RFLP print has been obtained. Thus, DNA information that may be legitimately obtained from tissue samples must be limited solely to identifying information. This limits markedly the potential for interference with privacy.

    An exception to this general caveat exists where bodily tissue which is believed to be the perpetrator’s has been obtained from the crime scene and no match with a suspect has been made. Under these circumstances, the police may wish to obtain from the DNA sample, the visual characteristics of the perpetrator (such as gender, hair and eye colour, etc.), and perhaps also information about whether the person has certain genetically determined medical conditions, in order to narrow down the class of possible suspects.

    As yet, DNA testing has not advanced to the stage where much of this information is available through genetic testing, but such tests will be available sooner or later (probably sooner), and there is no reason to deny law enforcement officials access to this information if it is used strictly for law enforcement purposes. However, once a match has been made with a suspect’s DNA, any diagnostic information about genetically based medical conditions that has been obtained from DNA found at a crime scene loses its significance as a law enforcement aid. It is our position that this information should be destroyed and not banked with identifying DNA information.

  2. Demand for a DNA Sample Without a Warrant

    Police should not have the power to demand a DNA sample from a person without a warrant merely because they suspect the person committed a crime. The spectre of the police rounding up citizens and taking DNA samples from them, by force if necessary, is unacceptable in a democratic society. We require a warrant for the search of a suspect’s home, and we should require no less for what is in effect a search into a person’s body. This is true even though the information obtained is limited to identifying information, and contains no information about genetic predispositions or characteristics. Reasonable and probable grounds to believe that a DNA test will implicate them in a crime ought to be the threshold for such a search.

    It is true that we allow the police the power to demand a breath (or blood) sample when the person is suspected of impaired driving. But the need to obtain breath/blood samples in a timely matter in these cases, and the fact that we do not allow the police to use force to obtain such samples, show that this case cannot be generalized into an argument for letting police demand samples of DNA without a warrant. A person’s genetic structure is not going to change over time, and it would invite authoritarian police practices if they were permitted use their own judgment to force persons they viewed as suspects to provide DNA samples. A warrant procedure for obtaining DNA samples will not interfere with law enforcement interests, and is required in these circumstances to ensure that citizens’ rights to privacy and non-interference by police are preserved.

  3. Demand for a DNA Sample With a Warrant

    By requiring a warrant, we require that the police be able to demonstrate to a neutral and impartial person able to assess whether the appropriate standard has been met that they have reasonable and probable grounds to believe that a DNA sample would yield evidence that the person committed the crime being investigated. That is, the police would have to have a DNA sample from the crime scene where an indictable offense had been committed, and have independent evidence that the person was at the scene of the crime at the time the crime was committed. In addition, a DNA test would in many circumstances provide virtually conclusive proof that the person was guilty, or alternatively that the person was innocent. It is difficult to construct a better rationale for issuing a search warrant. The BCCLA would limit the types of tissue that could potentially be demanded under a warrant to blood (from a pin-prick to the finger), skin cells from a mouth swab or scraping, and hair from the head. The demand for other samples would be unnecessarily invasive, given that any one of these three would normally yield a DNA sample of sufficient quality for matching purposes.

    The BCCLA understands that under normal circumstances, with proper care taken by the person who is taking the sample, each of these methods can reliably and efficiently yield a sample of sufficient quality for matching purposes. The operative principle in selecting among these methods is that the least intrusive method of testing be undertaken, and that means that taking tissue via mouth swabs or scrapings should be the preferred method of obtaining samples unless there is some reason to think that a good sample cannot be obtained this way.

    Again, there is no reason to think that regulating investigative procedures in this way would interfere with law enforcement, and it does most to preserve a suspect’s rights to privacy and to control over his/her physical person. Taking more invasive measures without clear need constitutes gratuitously punitive behaviour and an unjustified invasion of physical integrity.

  4. Warrants Should Be Obtained From a Judge

    Currently, search warrants are obtainable from Justices of the Peace. The BCCLA believes that having JPs issue warrants for DNA samples does not ensure a sufficient level of judicial scrutiny over these decisions. In these cases, it will be important to obtain tissue samples under controlled conditions because of the susceptibility of DNA samples to be damaged in a variety of ways (from heat, sunlight, etc.). In all likelihood, this will mean that suspects will have to be taken into custody and presented at a forensic laboratory to provide samples of DNA. It is also relevant that the search will involve an interference with the physical integrity of a person, even though it is a relatively minor one.

    Both the interference with physical integrity and the restrictions on a person’s freedom of movement make the execution of a DNA warrant a matter of greater moment for the rights of individuals than the interventions that are normally contemplated by the issuance of search warrants. These special circumstances justify a higher level of judicial scrutiny over warrant applications for obtaining DNA samples, and we therefore recommend that such warrants be obtainable only from a judge. The BCCLA is also concerned about the ease with which the police are currently able to obtain warrants from justices of the peace. In several recent incidents the police were able to obtain search warrants on weak or questionable evidence, with tragic results.

    A like concern was expressed recently by Mr. Justice Wallace T. Oppal in the Report of the Commission of Inquiry into Policing in British Columbia (1994). It appears that some justices of the peace have far too close a relationship with the police, and issue warrants virtually on demand. This raises the possibility that the warrant procedure for obtaining DNA samples could be a mere pro forma affair, and result in DNA samples being obtainable on mere suspicion, or virtually on demand. We believe that judges will have a better grasp of the greater seriousness of the issues that are involved in obtaining DNA information, and that they are less likely to adopt the practices for which justices of the peace have been properly criticized.

  5. Obtaining a DNA Sample Upon Arrest for an Indictable Offence/Banking DNA Information on Conviction

    DNA samples obtained for identifying purposes may be demanded from a suspect who is charged with an indictable offence. This information may be retained, however, only upon conviction for an indictable offense. If a suspect is found not guilty, the presumption of innocence that is part of our criminal justice system requires that the DNA information be returned or destroyed. This parallels our position on fingerprint information. We can see no compelling reason to treat DNA information differently, and the parallels with fingerprinting create a strong presumption in favour of treating it in the same way.

    As with fingerprints, DNA information represents an important law enforcement tool that will allow police to determine whether there is any reason to think that a suspect in one crime has been involved in other crime. Moreover, it is information that will aid police most directly in solving the most serious types of crime, that is, violent crimes including assaults, sexual offences, murder, and so on. It is a sad fact that persons involved in serious crime (indictable offences) are most likely to be involved at some time in other serious criminal activity, including violent crime. It would thus have very serious social costs to limit the collection of DNA information to those charged with violent offences and thereby deny ourselves the deterrent potential that banking DNA information may have on persons who have committed indictable offences and the opportunity to solve violent crimes these persons may already have committed or may go on to commit. These broader considerations were clearly an important part of the rationale for fingerprinting suspects in indictable offences, and if anything they apply more strongly for taking DNA information from suspects.

    We also find it difficult to find a compelling reason to deny police access to DNA information via warrants in cases of serious but non-violent crimes where that information may be relevant (see previous section). It is likely that from time to time such information will be useful in investigating and prosecuting frauds and the like; and it is also likely that such crimes will have at times equal or more devastating consequences for persons than certain violent crimes. We think therefore that drawing lines between classes of indictable offenses would inevitably be arbitrary and would unduly handcuff law enforcement.

    Finally, we do not think that the greater privacy interests that are at stake in obtaining and handling DNA information are sufficient to outweigh these potential benefits. The sorts of protections to privacy interests that are proposed here will strongly limit the potential for abuse on the part of law enforcement. If these conditions are met, we think that the case for treating the banking of DNA information like fingerprinting is compelling. We recognize that this policy has not yet been adopted in many jurisdictions, but we cannot see any good reason for limiting the resources of law enforcement beyond what we have proposed.

  6. Collection of Discarded Bodily Tissue

    The collection of discarded bodily tissue by police raises a number of difficult issues. We recognize that police should be permitted to collect such information, where it is relevant, if it is found as the result of the execution of a regular search. But it is our view that the police should be prevented from compiling data banks of DNA information on persons drawn from discarded body tissue. It is our position (explained above) that DNA information should be banked only for those convicted of indictable offences. Banking information on a wider range of persons, and possibly drawing on discarded tissue for this purpose, will bring the administration of justice into disrepute by extending the level of police surveillance of law abiding citizens to too high a level and by putting too many innocent people under the net of police suspicion. As well, such practices will undoubtedly encourage police to operate on the principle that everyone tangentially related to an investigation is a suspect until proven innocent. We want our law enforcement officials to operate on a different principle, namely, that people should be treated as though they are innocent by law enforcement authorities at least until there is some good reason to bring them under suspicion.

    The BCCLA recommends that the police should be statutorily prevented from generally collecting discarded bodily tissue for the purposes of banking DNA information. The exception to this is where such tissue is found at a crime scene and police have some reason to think that it belongs to the perpetrator of the crime.

  7. Laboratory Regulation

    Laboratories conducting DNA analysis for criminal investigation purposes will have access to very sensitive information. Parliament should legislate accreditation or licensing requirements for such laboratories, which would include requirements for the confidentiality and protection of both the tissue samples and RFLP results, and for the destruction of these. Regular audits should be included. Parliament should create a Criminal Code offence for anyone using tissue samples collected under this statute for DNA analysis other than that authorized under this statute or for possessing or disclosing such information.

  8. The Future of Genetic Screening

    Much of the concern about the privacy implications for DNA testing has to do with speculation that tests will soon be developed to identify a wide range of genetically based medical or psychological conditions or illnesses, and that police will be interested in having this information. The legitimate use of such information by law enforcement is highly dubious, and people are rightly concerned about the potential for invading privacy and stigmatizing persons if such information were to be held or disseminated by law enforcement authorities. However, very few such tests currently exist and the potential for abuse along these lines is accordingly still quite small. Time may change this, but the recommendations here imposing restrictions on the types of screening tests that may be used should limit much of the potential for abuse.

    Another point should be borne in mind. It is not clear how much motivation law enforcement authorities will have to track down genes that, if they exist, are correlated with certain antisocial psychological dispositions. If these genes can be identified, they may, if anything, be of more use to criminal defence lawyers in providing exculpatory defences to their clients than they would be of use to police. It remains to be seen just how strongly law enforcement agencies will be motivated to test for genetic traits beyond merely identifying traits.