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Andrew Haesler SC
Deputy Senior Public Defender
DNA Deoxyribonucleic acid - DNA is found in all cells, except red blood cells. Matching can be a wonderful investigative tool for police. DNA evidence can provide powerful evidence in support of a prosecution case. DNA evidence can also provide convincing evidence of a person's innocence.
A profile taken from the DNA of a suspect can be compared with the profile of a sample of DNA taken from a crime scene. A statistically validated 'match' or 'link' between these profiles is compelling evidence that they come from the same source. It may or may not, depending on the other evidence, be compelling evidence of guilt. Profiles can be stored on a computer database. They can be easily cross-checked and any linkage between a crime scene and a suspect's DNA sample investigated.
DNA is corroborative evidence. It is particularly useful if supported by statistics that the chance of someone else other than a defendant leaving the crime scene stain has a high probability ratio, such as one in ten billion.
DNA evidence can however be misunderstood M Findlay & J Grix, Challenging Forensic Evidence, (2003) 14 Current Issues in Criminal Justice 269 at 273. DNA's apparent certainty can be deceptive. It can be misused and misapplied. It will not of itself solve the crime problem although the chance of discovery may act as a deterrent Jacobs J in Griffith v R (1977) 137 CLR 293 at 327, noted: 'The deterrent to an increased volume of serious crime is not so much heavier sentences as the impression in the minds of those who are persisting in a course of serious crime that detection is likely and punishment will be certain'. DNA evidence is part of a prosecution case, it is not a panacea.
A study of juror's reactions to DNA evidence produced the following illuminating responses Rhonda Wheate, unpublished PhD thesis, ADF Academy/UNSW, May 2006:
Most of us would admit to similar opinions. We all want evidence and results that make our already difficult jobs easier. We would love some expert to ease the burden of judgment by saying, 'this is the answer'.
If only it were that easy. There's still a lot we don't know about DNA ' As we know, there are known knowns. There are things we know we know. We also know there are known unknowns. That is to say we know there are some things we do not know. But there are also unknown unknowns. The ones we don't know we don't know.' Donald Rumsfeld, US Secretary of Defence, Dept. of Defence Briefing, Washington 12 Feb. 2002. We need to be acutely conscious of the limitations of DNA evidence. It can be misused and misunderstood.
In this paper I look at how DNA evidence is used, and on occasions misused, in a Local Court context. I do not cover the science or the statistics involved in DNA analysis or the procedures set out in the Crimes (Forensic Procedures) Act 2000 (the Act). Reviews of the science, statistics and law can be found in a number of papers available on the Public Defenders webpage.
What I do here is look at some the following areas ' If I know the answer, I'll tell you the answer, and if I don't, I'll just respond cleverly', Donald Rumsfeld again:
Here are 6 points to remember about the science and statistics:
The Act operates as a facilitation mechanism for the collection of DNA and other forensic material. A good summary of the Act, particularly the provisions relating to taking samples from children or mentally ill people can be found in a decision of Simpson J - F V v Zeitler [2007] NSWSC 333.
A Magistrate can order that a suspect provide a forensic sample (ss 24 & 25). The Act also allows police to request a suspect to undergo a forensic procedure. A senior police officer can order that a person under arrest provide a non-intimate sample (ss.17 to 20). The Act provides for the making of interim orders where consent is not given or is unable to be obtained and for final orders to be made by a Magistrate before the sample taken can be analysed.
The Act provides a Code for the taking of samples and other forensic evidence from a person. The Act is said to strike a necessary balance between the appropriate use of available scientific means for investigating suspected crime and the historic rights of citizens against self incrimination. Fawcett v Nimmo & anor (2005) 156 A Crim R 431 Grove J at [14] In Orban v Bayliss [2004] NSWSC 428, Justice Simpson pointed out that the Act requires a positive finding that the person to be tested is a 'suspect':
'The conditions that must be met, before an order can be made, demonstrate that the purpose of the legislation is not to enable investigating police (or other authorised persons) to identify a person as a suspect; it is to facilitate the procurement of evidence against a person who already is a suspect'(At [31]).
The annexed tables summarise the procedures that must be followed in order to obtain a sample using the Act.
Before a sample can be requested there must be reasonable grounds to believe that the procedure will produce evidence that will prove the commission of an offence (s. 11(3)).
Where a Magistrate is asked to make an order or confirm an interim order, although the initial suspicion is that of the police investigator, the statute explicitly requires that the Magistrate be satisfied on the evidence before the Court, not the assertions of the police officer. Fawcett v Nimmo & anor (2005) 156 A Crim R 431.
A Magistrate considering an application under sections 24 or 25 can take into account hearsay material L v Lyons (2002) 56 NSWLR 600 per Sully J. The evidence does not have to be in admissible form or even strictly admissible (eg. hearsay is allowed) as long it is properly before the Court Hardy v Pinazza, unreported SCNSW, 18.4.2005, Adams J.
If the matter is reviewed by the Supreme Court (s. 115A) the question to be asked is whether it was open for the Magistrate to find, on the evidence before him or her, that there were reasonable grounds for suspecting Simpson J in Regina v. Rondo [2001] NSW CCA 540 at par 53 summarised the law in relation to reasonable suspicion:
(a) A reasonable suspicion involved less than a reasonable belief but more than a possibility. There must be some thing which would create in the mind of a reasonable person an apprehension or fear of one of the state of affairs cover by s 357E. A reason to suspect that a factor exists is more than a reason to consider or look into the possibility of its existence.
(b) Reasonable suspicion is not arbitrary. Some factual basis for the suspicion must be shown. A suspicion may be based on hearsay material or materials which may be inadmissible in evidence. The materials must have some probative value.
(c) What is important is the information in the mind of the police officer (undertaking the relevant course of action). Having ascertained that information the question is whether that information afforded reasonable grounds for the suspicion which the police officer formed. In answering that question regard must be had to the source of the information and its content, seen in the light of the whole of these surrounding circumstances.' See also Helen Maguire v Jason Beaton [2005] NSWSC 1241 162 A Crim R 21, per Latham J that the person had committed the prescribed offence, and that the requested material would assist in the poof of that offence.
The Magistrate must articulate the basis on which he or she was satisfied that the plaintiff was a suspect or a challenge will succeed. Maguire v Beaton (2005)162 A Crim R 21, per Latham J Similarly, if the Magistrate fails to articulate the reason why an application was refused a challenge will succeed. Alessi v SE and Anor [2008] NSWSC 909, Barr J.
An example can be found in Maguire v Beaton (2005) 162 A Crim R 21, per Latham J. Her Honour set aside the Magistrate's order for the taking of the plaintiff's fingerprints and palm prints because there was insufficient evidence to justify making an order pursuant to s. 24.
Police had arrested Mrs Maguire's son in possession of suspicious items and found keys relating to a storage unit. During the execution of the search warrant on the unit, guns and drugs were found, so too were documents relating to the lease of the unit with Mrs Maguire's name on them. Fingerprints implicated the son. Other prints were unidentified. The Magistrate required Mrs Maguire to give her fingerprints and palm prints.
The decision was challenged on the basis that the Magistrate's determination that Mrs Maguire did not come within the definition of 'suspect' for the purposes of s 25(a) of the Act and the Magistrate's had not properly determination that there were reasonable grounds to believe that the suspect had committed an offence for the purposes of s 25(c).
Justice Latham held that the Magistrate could not have been satisfied as a matter of law that the plaintiff was a suspect as there was no evidence of anyone resembling her ever having attended storage unit, nor could she be identified from surveillance footage at the premises. Mrs Maguire' had no criminal record, she was a woman in her late fifties who had been respectably employed for some time and she exhibited no trappings of unexplained wealth. At best there was a suspicion or mere speculation on the part of police that the plaintiff had leased the unit.
A police officer's assertion of suspicion in the affidavit grounding the application was not enough nor was a suspicion that the plaintiff may have leased the unit.
Again, in Hardy v Pinazza, SCNSW unreported, 18.4.2005 The judgment does not appear on the SC computer database., Justice Adams overturned the decision of the Magistrate because there was nothing in his reasons or the evidence that demonstrated he had reasonable grounds for believing the suspect had committed the relevant offence See also Maguire v Beaton, [2005] SCNSWi241 per Latham J.
Another example is the decision of Hall J in Walker v Bugden (2005) 155 A Crim R 416. There his Honour held that before a Magistrate could be satisfied that there were reasonable grounds for believing that a forensic procedure might produce evidence, the factual foundation for that belief had to be established. In short, before a court can order DNA be taken from a suspect, there has to be some evidence there was DNA from the crime scene to which it could be compared.
Care must taken to ensure that the strict procedural requirements of the Act are followed and complied with. The Act is not a carte blanche to facilitate the placing of everyone's DNA on a database. However, as long as there is evidence to support the conclusions reached and orders made and they are made in terms of the Act, a challenge to a Magistrate's order will not succeed Jawasansher v Johnson LCM [2004] NSWSC 872, per Barr J. F V v Zeitler [2007] NSWSC 333. per Simpson J.
It is harder again to challenge interim orders. The provisions relating to interim orders do not have the safeguards that can be found in s.25 (final orders). Interim orders are intended to preserve evidence that may otherwise be lost and are by their very nature emergency measures where time is of the essence. No order (including analysis) may be made unless the requirements of s 25 are met and a final order applying all the safeguards is made. See JW v Detective Sergeant Karol Blackley & Anor (2007) 172 A Crim R 483, Simpson J.
Generally, if there is some flaw in the process, this should be raised to argue against the admissibility of the evidence at trial: see s 80 and s 138 of the Evidence Act 1995. Obtaining a order to restrain testing is unlikely to succeed. Kerr v Commissioner of Police [2001] NSWSC 637 per Studdert J and JW v Detective Sergeant Karol Blackley & Anor (2007) 172 A Crim R 483.
The Act cannot be used to compel a person to provide a sample or undergo a procedure, which is not authorised, e.g. a urine sample. Alessi v SE and Anor [2008] NSWSC 909, Barr J.
The Act can be abused. As a consequence it contains some protections. These are designed:
'To maintain a delicate balance between preserving the traditional rights of citizens and individuals, including those suspected of crimes, to decline to participate in investigations or to cooperate with investigating authorities, and the overall interests of the community and of justice in facilitating the investigation of crime and the administration of justice, in securing the conviction of the guilty and the non-prosecution or acquittal of the not guilty. The Act was a specific response to scientific and technological developments but in the context of valued traditional civil liberties.' Orban v Bayliss [2004] NSWSC 428 Simpson J at [30].
At Committal: Even if there is other evidence implicating the defendant, DNA expert evidence is of such importance that there can be substantial reasons, within the meaning of s.91 Criminal Procedure Act, for attendance of the expert to give evidence at committal R v Micallef [2001] NSWSC 1172 per Hidden J.
Illegally obtained evidence:
The exclusion of evidence unlawfully obtained is a necessary role of the trial court Kerr v Commissioner of Police [2001] NSWSC 637. Part 9 of the Act deals specifically with questions of inadmissibility; of course section 136, 137 and 138 Evidence Act also apply. If the strict requirements of sections 24 or 25 are not met then, as noted above, exclusion of the evidence can be warranted. A failure to exclude evidence can lead to a successful appeal on the basis that there has been an error of law.
Often the desirability of admitting the evidence the subject of challenge will outweigh the undesirability of admitting such evidence. If the evidence was obtained in contravention of the Act R v White [2005] NSWSC 60 per Studdert J. the failures of the police or others must be carefully examined and weighed in terms of s.82 Which is the equivalent to s. 138 Evidence Act. As always with exclusionary provisions, were the discretion of the Court is enlivened, everything depends on the nature of the impropriety.
The collection of DNA by subterfuge has been allowed and sits outside the provisions of the Act. The Act does not apply to the chance circumstance that a suspect throws away an item such as a cigarette butt which is then retrieved without any reference to, or interference with the suspect, even if that 'chance circumstances' is manufactured by police desperate for a sample, which may not have been ordered by a Magistrate DNA has been obtained without recourse to the Forensic Procedures Act in a number of matters. See R v Kane (2004) 144 A Crim R 496, R v White [2005] NSWSC 60 per Studdert J., R v Nicola [2002] NSWCCA 63, where it was taken from a discarded Styrofoam cup. R v Hun, VSC, 16.6.2000, Vincent J, where it was obtained from a discarded cigarette butts and R v Daley, [2001] NSWSC 1211 Simpson J where a discarded RBT tube was used. Even if a forensic procedure is undertaken illegally, a civil court will be very reluctant to intervene to prevent the results being analysed. Exclusion of such evidence should generally be left consideration by the court of trial, Kerr v Commissioner of Police [2001] NSWSC 637 per Studdert J.
Other improprieties may not be so readily excused. For example, where police break into someone's house to steal their toothbrush. Examples of cases where District Court Judges have excluded unlawfully obtained evidence, or where the DPP has elected not to offer that evidence, include:
There is an important distinction between sections 82 and 83. Section 82 allows the court discretion to admit the evidence, as with s.138 Evidence Act. Where material is required to be destroyed section 83 allows no discretion, 'the results of the analysis, and any other evidence, are not admissible s. 83(2).
Section 137 Evidence Act: The fact that scientific evidence is complex does not mean that it will result in unfair prejudice and exclusion by the operation of s.137 Evidence Act. Complex evidence must still be received and any conflict of scientific evidence must be resolved by decision. R v Lisoff [1999] NSWCCA 364.
Section 137 is only engaged where the probative value of the evidence is outweighed by its unfairly prejudicial effect. Unfair prejudice arises where there exists the probability that the evidence may be misused in some way other than for the purpose for which it was placed before the court R v BD (1997) 94 A Crim R 131 at 139; R v Serratore (1999) 48 NSWLR 101 at [31], R v Taylor [2003] NSWCCA 194 at [93] and Papakosmas v The Queen (1999) 196 CLR 297 at [91]-[93]. A balance, analogous to the exercise of a judicial discretion, must be made of the evidence's probative value against the danger of unfair prejudice to the defendant. The task involves consideration of the evidence, the particulars of the case and the Court's own experience. If the probative value of the evidence adduced by the prosecutor is outweighed by the danger of unfair prejudice to the defendant there is no residual discretion, the evidence must be rejected. R v Sophear Em [2003] NSWCCA 374 and R v Blick, (2000) 111 A Crim R 326.
Section 137 thus could not be used to avoid determining an issue such as complexity but it could be used, as it was in R v Sing (2002) 54 NSWLR 31 (see below), to say that a DAL report without evidence to support it was inadmissible. Courts should be scrupulous in ensuring that samples collected by subterfuge are properly handled and the procedures in place for collecting lawfully ordered swabs be followed. Courts must be alert to the danger of contamination, accidental or deliberate. If unfair prejudice exists because of the way an exhibit is handled the exclusion of the evidence is warranted.
It is important to note that unless the Act requires destruction of a sample or an order ruling the evidence inadmissible is made there is no provision for ordering the destruction of samples or profiles taken pursuant to the Act. Charara v Commissioner of Police [2008] NSWCA 22 at [100].
The standard report prepared by the Department of Analytical Laboratories is usually brief and to the point ' I'm not into this detail stuff, I'm more concepty', Donald Rumsfeld again;
'The accused has the same profile as the DNA recovered from the crime scene sample. This profile is expected to occur in fewer than one in ten billion individuals in the general population'.
The explanatory note that accompanies the report contains these important qualifications:
'The final statistical calculation... does not prove uniqueness, but provides strong support for the hypothesis (without taking other evidence into account) that the DNA from the evidence sample originates from the matched individuals. The profile frequency calculation does not apply to closely related individuals' (Emphasis added).
As with all legal documents it pays to read the fine print!
The report simply notes the results of the analysis. It does not describe the process by which the result was obtained. In R v Sing (2002) 54 NSWLR 31 See also R v Ryan [2002] VSCA 176., the Court of Criminal Appeal held that, unless admitted by consent, the evidence from the expert who prepared the final report itself was not admissible. To make the evidence admissible, the chain of custody and handling of the exhibit from which the DNA was taken and analysed must be proved - from collection of the sample to final analysis.
This means that, unless the defence do not require them, everyone who handled, processed and analysed a sample should be called for cross-examination. The rationale for the decision was the danger of unfair prejudice that might arise if relevant witnesses were not called. A related issue was whether the expert's conclusions, reliant as they were on hearsay, were admissible in any event.
Recently the NSW police have taken to referring-out analysis of crime scene samples to a private DNA analysis firm. The DAL report simply notes that these outsourced samples have been compared to the results obtained in the DAL laboratory. The Report provides no assertion, or evidence of, no continuity between the crime scene sample and the subsequent analysis. It simply purports to report the results of matters, which were not even analysed in the same laboratory! The Report would not be admissible except by consent.
Another shortcut involves the service and tender of DAL forms indicating that a crime scene sample has been matched on the database with a particular offender profile. This note does not even purport to be an expert report however the prosecution rely on it as proof that the suspect did, as a matter of fact, leave the sample found at the crime scene.
The standard report does not contain sufficient material to found its admission over objection. The opinion rule s. 76 Evidence Act. precludes the reports admission unless it can be shown that the opinion in it is substantially based or the author's training study or experience s. 79 Evidence Act. These requirements were dealt with comprehensively by Justice Haydon in Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705 at [85].
Despite these potential problems in many cases the defence will allow the report to be tendered without objection or it will be tendered pursuant to s.177 Evidence Act. There should be more challenges. Evidence particularly relating to the collection and handling of DNA samples or exhibits from which they are taken should not be accepted uncritically.
Impressive statistics can indicate that it is unlikely that another person would have the same DNA profile as the defendant and the crime scene stain. Where that statistical certainty is challenged careful attention needs to be paid to the nature of the challenge. If the prosecution has not excluded the possibility of the accused having a sibling or other relative who may have left the sample, or where the expert called cannot support the statistical or population genetics behind their opinion, then the apparent certainty of the model used may be undermined.
So too, if there is other evidence that contradicts the DNA results. Examples recently accepted by juries (or the DPP in no-billing matters) include alibi and where the victim's description of the offender simply failed to match in any reasonably acceptable way the description of the person matched by DNA linkage to the crime.
There is fertile ground for cross-examination of both police and DNA analysts in the following areas.
The danger that the statistical significance of a DNA match has been overstated. Some of the risks attaching to DNA evidence are only now becoming apparent. 'The highly subjective nature of the mathematical process remains concealed behind the apparent certainty of a bald statistic', Mathew Goode, 'Observations on evidence of DNA frequency' (2002) 23 Adelaide Law Review 45 at 66-67. Examples include; the Eichelbaum-Scott report on DNA in New Zealand in 1999 The Rt Hon Sir Thomas Eichelbaum and Professor Sir John Scott, Report on DNA anomalies for The Hon Tony Ryall, New Zealand Minister for Justice, 30 November 1999, the inquiry in Victoria into how a female crime victim's DNA was found in the Jaiyden Leskie murder, the more recent problem of contamination in the Gesah case The Age 22 July 2008 and 8 August 2008 and the number of what are called 'unresolved pairs' often found when the data bases are searched for unexplained matches. Forensic DNA Evidence Interpretation, Buckleton, Triggs & Walsh CRC (USA) 2004 page 463. In 2005 Walsh and Buckleton reviewed Aboriginal DNA data bases for the National Institute of Forensic Science, in an unpublished report 'on Duplicate detection' they noted that out of a sample group of 33,858 there were 1,575 matches, 206 occurred at 9 loci or greater. They explained these as being; coincidental matches between unrelated individuals, the same person giving more than one sample underran alias, close relatives matching or identical twins matching. The report also noted that in New Zealand a similar review had found 64 unresolved matches from a database of 50,000 people. Where DNA is the only evidence or is critical to the case against the defendant, significant care must be taken when evaluating its efficacy in proving the prosecution case.
When the Crimes (Forensic Procedures) Act 2000 (NSW) was introduced the Police Minister Paul Whelan was explicit: Hansard, NSW Legislative Assembly, 31 May 2000, p 6293.
'It is important to note that DNA will be only one tool in the police officer's kit. They will still need to assemble a brief of evidence against the offender; DNA alone will not convict!'
In R v Pantoja, (1996) 88 A Crim R 554 at 559, Hidden J agreeing. Justice Hunt made the same point.
Although our understanding of DNA has advanced since 1996, the point still remains valid. A DNA link or match between the accused and a crime scene stain demonstrates only that the accused could be the offender. It does not establish that he was the offender.
In Pantoja Justice Abadee J Ibid at 583 and 584. put it much more empathically. He held that the tribunal of fact must first be satisfied beyond reasonable doubt that there is a match between the two profiles. That means only that the defendant cannot be excluded and therefore it is possible he left the crime scene stain. Further, the matching results could not, in the absence of other evidence, prove beyond reasonable doubt the defendant was responsible for the crime scene stain.
In R v Watters, [2000] EWCA Crim 89. it was emphasised that, there was no rule, that when the statistics reached a certain level a prima facie case could be established. Rather, it was emphasised that the DNA evidence must be evaluated in the context of the other evidence in the case.
Pantoja was decided in 1988. Courts have subsequently expressed greater confidence in DNA and how it is presented. In R v Galli, the Chief Justice said: (2001) 127 A Crim R 493 at [98].
'The courts have approached DNA evidence with caution. However that caution is naturally abating as experience with the use of such evidence has grown'.
There have been strong statements in support of the proposition that DNA should be treated like fingerprint evidence which has been held to be good enough to justify a conviction on this evidence alone: R v Rowe [2004] SASC 427 at [40] (SA CCA). R v Galli (2001) 127 A Crim R 493 at [106] per Spigelman CJ.
'If the results indicate that it is at least 10 billion times more likely that the crime scene sample originated from the accused than from any other unrelated person selected at random from the population, then if the evidence is sound then beyond any doubt the accused is the offender. To paraphrase Anderson J in R v Shaheed [2002] 2 NZLR 377 at [207].'
In most cases I have reviewed there is some other evidence, insufficient of itself to prove guilt, which the DNA evidence corroborates. Examples include: R v Gum [2007] SASC 311, where there were similarities in appearance between the accused and the alleged rapist; R v Fitzherbert [2000] QCA 255, where there was evidence of animosity and contact between the accused and the victim; R v Butler [2001] QCA 385 where the evidence was DNA and opportunity and R v Weetra [2004] SASC 337 where the accused lived nearby and stolen property was found near his home.
Prosecutors still however persist in bring cases based solely on DNA evidence without anything to support it other than a brief DAL report and no other evidence at all. In recent example the evidence consists of the DAL report where there was no evidence of continuity of samples and outsourced testing and a description of the attacker as a 15 year old Caucasian boy. The accused was a 25 year old Aboriginal man who the police could not prove was even in the State at the time!
I have yet to find a superior court decision where DNA alone has been used to convict: eg where the Crown could not prove the defendant was in Australia at the relevant time. There are however cases where the barest of other evidence and a DNA link between a defendant and a crime scene, to a very high probability, has been used to convict. An example is R v Rowe: a police officer could at best give a general description of his assailant but where blood from which was recovered DNA linked to the accused was found on the officer shirt. As such it was not strictly a DNA only case, although it came very close. Doyle CJ said:
'The appellant sought to argue that because the DNA evidence was the only evidence of identification of the appellant, the conviction was somehow unsafe and unsatisfactory. The evidence was the subject of expert opinion. It was subjected to close scrutiny by the trial Judge who directed the jury that they must be satisfied beyond reasonable doubt as to the reliability and accuracy of the DNA analysis. It probably founded a safer basis for a conviction than the frailty often attending the evidence of a single eyewitness who gives evidence of identification of an offender. There is no substance in this ground.'(At [40])
I note that despite this view where DNA is the only evidence, the usual, but not exclusive practise, of the NSW Director of Public Prosecutions is to no-bill the matter. The NSW police will however generally try it on.
Cases where DNA is the only evidence are understandably rare, but are becoming more common as more and more serious offenders are placed on the offenders' database. It was reported in The Advertiser of 28/8/2008 that South Australia had 41,161 profiles on its database, a 100% increase on a year before. Cold links are now being made, between crime scene stains and this database, with increasing frequency. Examinations of 'cold cases exhibits' have turned up nuclear DNA from exhibits over 10 years old, see R v Stone (2004) 144 A Crim R 568. Stone pleaded guilty in 2004 to a 1990 murder. Sometimes cases are presented to court solely on the basis of this link. More often the link leads to further investigations and other evidence such as admissions, opportunity, identification or motive is presented. The DNA link then provides powerful corroboration of that other evidence.
A DNA match shows only that it is possible to a very high degree of probability that the defendant is the person responsible for leaving the stain. Despite the power of the statistical analysis that accompanies DNA testing I argue this can never be enough to prove a case beyond reasonable doubt in the absence of some other evidence for the DNA to corroborate. As the court said in Pantoja all the DNA match or link shows is that they could be the offender. In most, if not all, cases there will be good reasons why the mere fact of a match and the giving of a high match probability cannot be viewed with the certainty necessary of itself to prove the prosecution case beyond reasonable doubt.
Where the prosecution can point to no other evidence to support or corroborate their case against the accused, the case cannot be proved on the necessary high standard.
Where there is some other evidence, common sense leads to the conclusion that before a case can be proved beyond reasonable doubt all relevant evidence (DNA and otherwise) must be considered in context. A useful starting point for submissions to a court considering DNA evidence comes from the leading South Australian decision of R v Karger (2002) 83 SASR 135, per Doyle CJ at 140-141. See my paper 'DNA in Court 2008'at pages 15 & 16, available off the public defenders webpage.
'The statistical evidence is undeniably strong evidence pointing to a conclusion that the accused was the source of the incriminating DNA, but is not direct evidence of that fact. And, as is obvious, the statistical evidence must be considered in the light of other evidence in the case'.
DNA is just evidence. It is another piece of physical evidence.
A DNA profile however is not real. It is a scientific and statistical construct. Even if the statistics are good questions can arise about how the match came about. This is an area we as lawyers know and understand as it involves questions of proof, evidence and weight of evidence. Often the question is not, 'Whose DNA is it?' but 'How did the DNA get there?'
Like all physical evidence DNA can be used, misused and abused. As with any piece of evidence, care must be taken to place that evidence in context and assess its weight, not in terms of statistics but how it relates to all the other evidence in the case.
Andrew Haesler SC
Carl Shannon Chambers
February 2009
20 Sep 2024