In 2012, Lukis Anderson was charged with murder. The case against Anderson was circumstantial – based solely on evidence of DNA transference. But it was later learned that his DNA had made it to the crime scene by way of the paramedics who had treated Anderson earlier on the same day, and later arrived at the victim’s residence – inadvertently transferring DNA evidence to the crime scene three hours later.
Anderson’s case has been described as a “definitive example” of how “absent appropriate skepticism and restraint” the criminal justice system’s reliance on DNA evidence, as infallible, “carries significant risks”, and may lead to “‘miscarriages of justice’”.
DNA Evidence Generally
As the carrier of each person’s genetic code, DNA profiles can be used as circumstantial evidence of identity. Since first being accepted in Canada, countless crimes which would have otherwise remained unsolved, have had suspects identified by DNA. Just as importantly, hundreds of wrongful convictions have been exposed as a result of DNA testing. As Justice Kerans observed 25 years ago, “assuming appropriate scientific care in gathering and testing” DNA evidence “is the most dramatic forensic evidence ever discovered”.
Courts have also been aware of the risks of DNA evidence, that a trier of fact may be tempted to equate “fantastic odds”, couched in terms such as ‘quintillion’, with the likelihood that the accused was guilty. This is taken with concerns such as the potential for contamination, laboratory error, and inadvertent transfer. In this respect, DNA analysis is too often viewed as a “crisp, objective, near infallible science”, or as a “crystal ball being handed to the criminal justice system”. But history teaches about the dangers of unreliable forensic expert evidence – and their connection to wrongful conviction. Those alive to history’s lessons should see recent developments in forensic DNA analysis as a call for heightened vigilance.
Secondary DNA Transfer
There are three ‘modes’ of DNA transfer, all based on Locard’s Exchange Principle.
Primary DNA transfer is the passage of DNA to objects and people. Where a perpetrator handles a knife, they may deposit DNA by way of primary transfer.
Secondary DNA transfer occurs where DNA is transferred between an object or person through an intermediary. For example, if two individuals shake hands, then one person handles a knife, DNA from the first person may transfer to the second during a handshake, and then is deposited on the knife when the second person touches it. Similarly, if one individual, then another, handles a knife, the DNA from the first person may be picked up by the second person.
Tertiary transfer occurs when there is indirect transfer through two intermediaries. For example, one person touches a doorknob, and then a second person touches the doorknob. A second person then handles a knife. DNA could then be transferred from the first person to the doorknob, to the second person who deposits the first person’s DNA on the knife.
The literature has now identified the need to distinguish between two very different questions: “[o]ver the last several years an increasing number of cases no longer question ‘whose DNA it is’ but wish to know ‘how or when it got there’”; scientists in forensic DNA analysis have identified “an increasing need to understand how the DNA within a trace got to where it was collected from”.
The first branch of inquiry, ‘whose DNA is it?’ relates to DNA comparison and statistical analysis. It enjoys reliable techniques for testing and an established base of literature. It is reflected in a plethora of investigations of primary transfer and under what conditions primary DNA transfer occurs.
The second branch, ‘how it got there and when’ is a very different question. In a 2019 article in the International Journal of Forensic Science, AH Roland and his colleagues identified this as a novel field of inquiry falling under the umbrella of ‘DNA transfer, persistence, prevalence and recovery’ (“DNA-TPPR”). Unlike DNA comparison, there is no consensus as to the nature and occurrence of secondary and tertiary modes of transfer. If there is any consensus, it is the present state of the science poses dangers to forensic DNA evidence being introduced in Court.
A ‘Paucity’ of Research and Empirical Data
DNA profiling allows results to be generated from small traces of DNA. Small amounts may not correlate with activity level, and DNA from an innocent person may be brought to the scene via secondary transfer. As Goray and van Oorschot explain, “[s]cenarios incorporating multiple DNA transfer steps, rather than direct transfer, are increasingly being raised in court as potential means for the presence of the defendants’ DNA at the crime scene or on a piece of evidence.” However, “little is published about DNA transfer in ‘‘uncontrolled’’ or real life situations”, and advancements in this area have not kept pace with other developments. Taylor and his colleagues note, absent further advancements, “by just the properties of the DNA profile obtained, no definitive conclusions could be made by an analyst as to whether it had resulted from primary or secondary transfer”. Cale notes there is “a paucity of research projects regarding the continued [or ‘secondary’] transfer of DNA”. Roland notes a “paucity of empirical data on the variables that may or may not impact DNA-TPPR”. Previous wrongful convictions have led to calls for caution in respect to assessments based on fundamental misapprehensions of the nature of secondary transfer.
In a 2016 study by Cale and her colleagues, subjects were asked to shake hands for two minutes, and then each handles a knife. In 85% of cases, the DNA of the other person was transferred to the knife. In one-fifth of the samples, the DNA analysis identified this other person as the main or only contributor of DNA to the ‘weapon’. In other words, in 20% of cases, secondary transfer resulted not only in a primary profile, but there was no DNA profile for the original individual.
In 2017, Goray and van Oorschot, of the Victoria Police Forensic Services Centre in Australia, conducted a lab experiment designed to mimic everyday interactions. Volunteers sat at a table and shared a jug of juice. After 20 minutes, subjects’ hands, the chairs, the table, the jug, and juice glasses, were swabbed and tested. Although volunteers never touched each other, 50% had another person’s DNA on their hand. One-third of the glasses bore the DNA of volunteers who had not touched them. Further, there were “several samples where the transferred DNA was a major component”. The authors conclude that this study shows how “communally used objects” can serve as ‘reservoirs’ of material available for DNA transfer.
In other peer-reviewed studies, it was found that 50% of subjects tested had the DNA of another individual on their neck, that 13%-15% people have traces of someone else’s DNA under their fingernails, that an area can be contaminated with the DNA of a stationary person speaking in as little as 30 seconds, and there are many more examples in the literature.
However, a cursory review of the literature shows that leading researchers continue to caution against the dangers inherent in the expert evidence as to DNA-TPPR, and expert evidence about the ‘how and when’ of DNA transfer. There is a broad acknowledgement that “a perpetrator of a crime could bring traces of another individual into a crime scene and deposit these traces via secondary DNA transfer”. This could “falsely link someone to the scene of the crime” and “could lead analysts and other medicolegal professionals to falsely conclude that DNA left on an object is a result of direct contact.”
Judicial Response to Risks of Secondary DNA Transfer – Trial Judge as ‘Gatekeeper’
Alongside a growing awareness of the risks of secondary DNA transfer, the reaction of Canadian courts has been varied. That said, in a number of promising decisions, Courts have shown an acute awareness of these risks.
On one front, Courts have continually acknowledged the need for rigid adherence to principles governing expert evidence. Expert evidence “is both immensely important to legal adjudication and equally dangerous”. The concern is where an expert witness, “veiled in their authority”, and bolstered by their “(often) superior knowledge”, provides evidence “cloaked under the mystique of science”, it may be perceived as “being virtually infallible” and “having more weight than it deserves”. History teaches of the dangers of expert evidence. In the worst of cases, “dubious expert evidence has contributed to wrongful convictions”. As such, procedural and evidentiary safeguards govern expert evidence, reflecting the trial judge’s obligation as gatekeeper, to safeguard the trial against prejudicial expert evidence, and to exclude it when it is not demonstrably reliable.
Expert evidence related to the question of ‘whose DNA it is’ falls squarely under the ambit of standard forensic DNA analysis. However, the issue of ‘how it got there and when’, is very different. And in circumstantial cases involving DNA evidence, it is often the ultimate issue. For this reason, in recent decisions, courts have been cautious about scrutinising the permissible scope of expert evidence related to secondary DNA transfer, and are beginning to appreciate the significance of this distinction.
For example, in R v Sabrie, a swab taken from the complainant’s breast contained the accused’s DNA profile. DNA evidence was central to the case. The trial judge found that the Crown had not advanced sufficient evidence to rebut the possibility of secondary transfer:
[w]hile the expert had concluded that some transference scenarios were more likely than others, her conclusions seemed to be grounded in common sense rather than as a result of scientific studies or testing. Absent more information about the scientific foundation for her conclusions, I find myself without any real ability to assess them and am cautious about placing any weight upon them. I am also mindful that Mrs. Shacker was qualified as an expert in the comparison and analysis of DNA. She was not qualified as an expert in the transference of DNA. It is critical that an expert be confined to giving evidence only in those areas that they have been properly qualified. I find that Ms. Shacker’s evidence about transference was outside of her area of expertise and as such impacts the amount of weight I am prepared to place upon it.
In acquitting the accused, the trial judge concluded that while she accepted that DNA was found on the complaint’s left breast “[w]hat I am not sure of is how it got there”.
In R v Hall, the accused appealed on the basis that the trial judge erred in his charge to the jury related to secondary DNA transfer. The MBCA found that the charge was sufficient. However, this was based on the absence of expert evidence as to “the likelihood of the manner of DNA transfer”. What is relevant, is that the MBCA noted the admissibility of such evidence is an “open question, at least in Canada”, citing the SCC decision in Awer.
R v Awer, was an appeal from a decision ABCA stemming from a conviction for sexual assault. At trial, there were competing experts, and a central issue related to the rate, occurrence, and possibility of secondary DNA transfer. The ABCA upheld the decision of the trial judge. In dissenting reasons, Justice Berger found that “one cannot reliably infer the origin or mode of transfer simply from the amount of DNA found”, and that “no ready-made inference” was available to be drawn from the presence of the DNA, to the potential mode of transfer.
The SCC overturned the decision and ordered a new trial on the basis that the trial judge did not assess the competing expert evidence in a balanced manner. Justice Moldaver observed that the SCC need not finally decide the issue of whether “the impugned evidence of the Crown’s DNA expert as to the source of the complainant’s DNA… was or was not admissible”.
In Canada, the full import of such decisions, and standards governing the admissions of expert evidence related to DNA-TPPR, and secondary DNA transfer, remains to seen. That said, a greater understanding of the phenomenon of secondary, and tertiary transfer, call for greater vigilance. As Justice Iacobucci cautions: “[t]o function well, the system requires that judges, lawyers and expert witnesses all do their part”.
Ridgid Adherence to Principles Governing Circumstantial Evidence
In addition to ensuring trial judges strictly adhere to their gatekeeping function, in recent years, Canadian Courts have been very careful in scrutinising the reliability of DNA evidence in circumstantial cases.
It has been found that “DNA evidence is powerful evidence that the person whose DNA is on the object was in contact with that object”. However, “the connection of the accused with the crime will depend on the existence of other evidence capable of establishing… contact with the object at the relevant time and place”.
In R v Grayson, the accused was charged with the theft of a vehicle, which was found abandoned two days later. The accused’s DNA was found on a balaclava located in the vehicle. The ONCA overturned his conviction and entered an acquittal, having applied the two-stage test set out in DDT. The court observed that “[t]he Crown cannot point to any evidence that makes the inference that the appellant was in contact with the garment in connection with the theft more likely than the inference that he was in contact with the balaclava at some other time”. Evidence of the accused’s DNA on the balaclava “only demonstrates that he likely wore the garment at some point in time”.
In R v McGinn, the accused was charged with offences stemming from an armed robbery of a liquor store. The case was based on DNA located on a neck-warmer located in a stolen car later that night. In reaching his decision, Justice Lee considered expert evidence related to the possibility of DNA transfer between persons, and the possibility that an individual could wear an item and leave no DNA at all. Justice Lee found that this “clearly establishes the limitations of that evidence”. He found that “the DNA evidence is only that at some point in time, the Accused’s DNA came into contact with the black neck warmer”. This was insufficient to establish identity.
In R v Galenzoski and Johnson,, two men were charged with break and enter. Evidence against the co-accused was circumstantial, based on DNA evidence from items recovered from the complainant’s property. One accused called a witness offering an innocent explanation for the DNA, while the other called no evidence and the court considered expert evidence related to secondary DNA transfer. It found that DNA evidence established, at best, that the accused persons had handled the relevant items, but, “so did at least one other individual”. Both accused were acquitted: “[t]he connections are just too tenuous and the possibilities too varied”.
R v Hodgson, involved an attack on a female. The complainant had broken free of her attacker, who dropped a glove during the struggle and fled, as confirmed by video footage. The Court considered evidence of clothing seized from the accused’s residence, argued to match the description in the video. The Crown’s case was otherwise entirely based on DNA evidence from the glove that matched the accused, or, as the trial judge described it “the possibility that the DNA in the sample came from somebody other than Mr. Hodgson is so statistically unlikely as to be insignificant”. The trial judge noted the evidence of a Crown expert, Ms. Popovic, that while the accused was a ‘major contributor’, there were also two minor contributors, whose samples were not suitable for comparison. The Court states as follows:
Ms. Popovic testified that she was unable to say whether the major contributor was the last person to have worn the glove, nor was she able to say when any of the samples were deposited. She gave no evidence as to what inferences, if any, could be drawn from the fact that there was a larger amount of DNA from the major contributor than from the minor contributors.
The Court identified the importance of DNA evidence and the need to “identify the limits of what [it] is capable of proving”. Significantly, the Court distinguished previous decisions in which DNA evidence was sufficient to establish guilt, because in those cases “only a single DNA profile was found on the items in question”.
The Court rejected arguments by the Crown that there was “no evidence that the unknown individuals who wore the glove matched the description or owned similar clothing” and found that to accede to such arguments would be “to fall into the error identified in Villaroman of requiring alternative inferences to be based on “proven facts”:
[e]ven if the Crown is correct that it is objectively improbable that one of the other two individuals who wore the glove fit the description and owned similar clothing, this establishes only that Mr. Hodgson was probably the perpetrator. Probable guilt cannot ground a conviction… In my view, to use the language of Villaroman it is a “plausible theory” or “reasonable possibility” that one of the other two unknown individuals who wore the glove matched the generic description and owned a black hoodie and beige shorts.
In the result, the Crown had not proven identity beyond a reasonable doubt.
In R v Donoghue, an accused was convicted of break and enter. It was admitted that the accused’s DNA was found in a glove, a purse, and on the kitchen counter. In a terse judgment, delivered curium from the bench, the ONCA overturned the conviction and entered an acquittal. It found the Crown had “called no expert evidence on the characteristics of DNA evidence or how it may be transferred”, or whether the “appellant’s DNA was the sole profile on the glove”. It states:
The evidence established that the appellant was connected to the glove. The evidence further established that the glove was clearly connected to the commission of the crime. However, standing alone, the DNA evidence led at trial was incapable of bearing the burden of proving that the appellant left the glove at the scene of this break and enter.
The decision confirms that “presence of the accused’s DNA is not determinative of guilt and does not lead inexorably to only one inference such as to support a conviction at trial”.
The import of these decisions is that there is a growing judicial awareness of the dangers of uncritical reliance on DNA evidence – particularly in ‘filling in the gaps’ in the evidence, occasioned by the absence of credible expert evidence as to the ‘how and when’ of DNA transfer.
The law is settled that reasonable possibilities that can be inferred from circumstantial evidence cannot be based on speculation but must be based on common sense and human experience. However, particularly in cases involving DNA transfer, our intuitions about what is possible or probable do not always accord with established science. While intuitively, possible inference based on seem highly ‘unlikely’ they are not impossible. They may, in the universe of what is ‘possible’ seem less unlikely than DNA transferring miles to a crime scene, by paramedics – as in the case of Lukis Anderson.
A growing awareness of the phenomenon of secondary and tertiary DNA transfer highlights the importance of the presumption of innocence, and why safeguards are required to protect against the dangers of unreliable expert evidence. Invalid science offered by a seemingly impressive expert “may distract from defective methodology”. A review of the literature demonstrates a lack of consensus on secondary transfer. What consensus there is, is a growing recognition this phenomenon can, and has, led to individuals being falsely linked to crimes.
In closing, the writer would call for all stakeholders in the criminal justice system remain vigilant, and exercise an appropriate degree of scepticism and restraint, in light of recent scientific advancements in this field. This is necessary to ensure concerns about secondary DNA transfer, and unsafe conviction, are meaningfully addressed, as part of our shared interest in the pursuit of justice.
 PA Smith, “When DNA Implicates the Innocent”, (2015) 314(6) Scientific American 11; The Marshal Project, K Worth “Framed for Murder By His Own DNA” Online: <https://www.themarshallproject.org/2018/04/19/framed-for-murder-by-his-own-dna> (accessed July 20, 2019).
 R v Hall, 2018 MBCA 122 at para 13.
 R v Parent (1988), 46 CCC (3d) 414 (ABQB) .
 T McDonald “Genetic Justice: DNA Evidence and the Criminal Law in Canada”, (1998) 26 Man LJ 17 .
 R v Love, 1995 ABCA 448 at para 24.
 R v Bourguignon,  (Ont Ct Gen Div), aff’d (1997), 118 CCC (3d) 43 ; R v Baptiste,  17 WCB (2d) 453 (BCSC) .
 T McDonald “Genetic Justice: DNA Evidence and the Criminal Law in Canada”, (1998) 26 Man LJ 16 at 16-18.
 EE Murphy, Inside the Cell: The Dark Side of Forensic DNA (New York: Nation Books, 2015) at ix.
 MA Godsey and M Alou, “She Blinded Me with Science: Wrongful Convictions and the ‘Reverse CSI-Effect’” (2011) 17 Tex. Wesleyan L. Rev. 481.
 E Locard, “The analysis of dust traces, Part 1”, (1930) 1 Am J Police Sci 276 .
 AE Fonneløp, T Egeland, and P Gill, “Secondary and subsequent DNA transfer during criminal investigations”, (2015) 17 Forensic Sci. Int. Genet. 155.
 RA Van Oorschot and MK Jones, “DNA fingerprints from fingerprints”, (1997) 387 Nature 1997 767.
 AH Roland, et al, “DNA transfer in forensic science: A review” (2019) Forensic Science International: Genetics 38 (2019) 140–166 at p 141 (emphasis added).
 Ibid at p 159 (emphasis added).
 G Meakin and A Jamieson, “DNA transfer: review and implications for casework”, (2013) 7 Forensic Sci Int Genet 434.
 M Goray and AH Roland, “The complexities of DNA transfer during a social setting” (2015) 17(2) Legal Medicine, 82 at 82.
 Ibid at 82.
 AE Fonneløp, T Egeland, and P Gill, “Secondary and subsequent DNA transfer during criminal investigations”, (2015) 17 Forensic Sci. Int. Genet. 155 .
 D Taylor et al. “Helping to distinguish primary from secondary transfer events for trace DNA” (2017) 28 Forensic Science International: Genetics 155 at 156. The authors are optimistic that it may be possible in the future.
 CM Cale, et al “Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime?” (2016) 61.1 Journal of Forensic Sciences 196 at 196.
 Ibid at 196.
 EE Murphy, Inside the Cell: The Dark Side of Forensic DNA. (New York: Nation Books, 2015) at 20, 29, 47.
 CM Cale, et al “Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime?” (2016) 61.1 Journal of Forensic Sciences 196 .
 M Goray and AH Roland, “The complexities of DNA transfer during a social setting” (2015) 17(2) Legal Medicine 82.
 E Graham, and G Rutty, “Investigation into ‘Normal’ Background DNA on Adult Necks: Implications for DNA Profiling of Manual Strangulation Victims” (2008) 53(5) Journal of Forensic Science.
 A Lowe et al., “The propensity of individuals to deposit DNA and Secondary Transfer of Low Level DNA from Individuals to Inert Surfaces” (2002) 129, Forensic Sci. Int. 25
 NJ Port et al, “How long does it take a static speaking individual to contaminate the immediate environment?” (2006) 2(3) Forensic Science, Medicine, and Pathology 157.
 See, for example, references in Roland, AH et al “DNA transfer in forensic science: A review” (2019) 38 Forensic Science International: Genetics 140.
 Ibid at 196.
 CM Cale, et al. “Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime?” (2016) 61.1 Journal of Forensic Sciences 196 at 196.
 J Chin, “Abbey road: The (Ongoing) Journey to Reliable Expert Evidence” (2018) 96 Can B Rev 422 at 424.
 R v Mohan,  2 SCR 9 at para 19; R c Béland,  2 SCR 398 .
 R v Bingley, 2017 SCC 12 at para 36.
 R v Abbey, 2009 ONCA 624 ; R v J-L J, 2000 SCC 51 .
 R v Sabrie, 2017 ONSC 6134.
 No weight was placed on the Accused’s evidence, and the Court also found that the ability of the complainant to recall rendered her evidence unreliable.
 R v Sabrie, 2017 ONSC 6134 at para 54 (emphasis added).
 R v Hall, 2018 MBCA 122.
 Ibid at para 155.
 Ibid at para 155.
 Ibid at para 155.
 R v Awer, 2017 SCC 2.
 R v Awer, 2016 ABCA 128.
 Ibid at para 113.
 Ibid at para 122.
 R v Awer, 2017 SCC 2 at para 6.
 R v Awer, 2017 SCC 2 at para 2.
 F Iacobucci, G Hamilton, “Goudge Inquiry and the role of medical expert witnesses” (2010) 182(1) CMAJ 53 at 56.
 R v Grayston, 2016 ONCA 784 at para 14.
 Ibid at para 14.
 Ibid at paras 14-19 (emphasis added, citations omitted).
 R v McGinn, 2015 ABQB 558.
 And attempted robbery of a gas bar.
 R v McGinn, 2015 ABQB 558 at para 7.
 Ibid at para 10 (emphasis added).
 Ibid at para 10.
 It bears note that Justice Lee also identified certain exculpatory evidence, specifically that it was possible that the Appellant may have been in custody on the night in question (at paras 12-15).
 R v Galenzoski and Johnson, 2019 BCPC 56.
 Ibid at para 30.
 R v Galenzoski and Johnson, 2019 BCPC 56 at para 30.
 Ibid at para 32.
 R v Hodgson, 2017 ONSC 6870.
 Ibid at para 12.
 Ibid at para 2.
 Ibid at para 2.
 Ibid at para 14.
 Ibid at para 15 (emphasis added).
 Ibid at paras 20-21.
 Ibid at para 26.
 Ibid at para 23.
 Ibid at para 23.
 Ibid at para 24.
 Ibid at paras 24-25 (emphasis added).
 Ibid at para 31.
 R v Donoghue, 2019 ONCA 534.
 Ibid at para 2.
 Ibid at para 3.
 R v Miller, 2019 ONCJ 480 at para 98, citing R v Donoghue, 2019 ONCA 534.
 R v Wuschenny, 2018 ONSC 6765 at para 73.