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  • Evan MacKnight (UNB Law Student)

R v Roy: The Use of K-9 Units in the Search for Truth (A Law Student’s Perspective)

A crucial element of the law of evidence is reliability. Many rules of evidence are designed with the purpose of excluding unreliable evidence which may unfairly persuade the trier(s) of fact and impact the court’s search for truth. When eyewitness testimony and expert evidence are combined, it creates a hurdle that must be overcome if the proffering counsel wishes for such evidence to be admitted at trial. R v Roy, 2016 NBCA 51, is a New Brunswick Court of Appeal case concerning a breaking and entering trial in which the Crown used dog tracking evidence to obtain a conviction. Dog tracking evidence is different from most types of evidence because the source of the evidence obviously cannot testify nor can it be cross-examined, and as such, it must be qualified by the expert opinion of a dog handler. Roy does not make a marked departure from jurisprudence as the decision made by the court errs on the side of caution and exercises deference to the trial judge. However, Roy is noteworthy because it focuses on the issue of credibility and the admissibility of dog tracking evidence.

Dominique Roy, the appellant, was found by police with the assistance of a K-9 unit.

The dog traced a scent from the scene of the crime and used it to track Roy through a wooded area to a highway that was close-by. The officer then commanded the dog to verify the scent by retracing the scent of the appellant back to the wooded area. The trial judge found that the boot print evidence was inconclusive and the crime scene lacked any other forensic evidence which placed Roy at the scene of the crime. Nonetheless, the trial judge accepted the officers’ testimony of Roy’s appearance upon arrest as well as the evidence given by the dog handler.

The appeal is largely based on the trial judge’s assessment of the credibility of evidence admitted at trial. The test used by the trial judge to determine credibility is quoted from a Supreme Court of Canada case called R v W(D).1 The approach to assessing credibility of evidence requires the trier of fact to acquit the accused if the accused’s testimony gives the trier of fact any reason to doubt the accused’s guilt. Even if the accused is unsuccessful in doing so, the accused must be acquitted unless the prosecution has proven its case beyond a reasonable doubt. The W(D) test is significant in Roy because the evidence proffered by the accused and the prosecution completely contradict one another and the judge’s decision boils down to an assessment of which version of events he finds more credible.

Roy’s testimony is received as being so vague and inconsistent that he loses all credibility as a witness. Roy’s lack of credibility in his testimony essentially adds credibility to the Crown’s evidence because it limits the potential number of rational conclusions that the court can draw from the evidence. Since Roy’s evidence does not raise any reasonable doubt as to guilt, the trial judge is free to use his or her discretion to side with the version of events given by the Crown if he or she finds that the Crown has proven its case.

Baird J.A., writing for the New Brunswick Court of Appeal, finds that while the test from W(D) is the correct test to apply in assessing credibility, it is only the principles of the test that need to be followed. This demonstrates the shift in the law of evidence towards the principled approach and away from a rule-based approach. This shift is not novel or unique to the Roy case, rather, it adds to the jurisprudence. The trial judge benefits from the principled approach in Roy by using his or her discretion to freely weigh the credibility of evidence without being confined by strict rules. What is significant to the Roy case is the court’s assessment of dog tracking evidence that formed the basis of the Crown’s case.

As mentioned earlier, the Crown had no direct evidence that implicated Roy and they relied heavily on the dog tracking evidence submitted by the RCMP. The test for reliability of dog tracking evidence comes from a 1962 British Columbia Court of Appeal case called R v Haas:

The evidence tendered should not be admitted unless the Crown first establishes the qualifications of the dog and its trainer. It is the dog’s propensities and skills that make the evidence of what the dog did admissible, just as it is a witness’s qualifications and training that establishes him as an expert that makes his opinion admissible. The qualifications of the dog, like those of an expert, must be proved.2

This excerpt suggests that dog tracking evidence is expert evidence and must be qualified as such. The court then lists eight factors used by the Crown to qualify the dog and dog handler. It is interesting to note that the Court of Appeal judgment does not mention any use of a Mohan test;3 the test commonly used by courts when qualifying expert evidence. The test employed in Roy is more stringent and specific to dog tracking evidence than the Mohan test, and that is likely why the court used that approach. Justice Baird maintains that this is the correct approach and exercises deference towards the trial judge’s findings of fact. A couple of implications can be drawn from the Roy decision. First, it could be that dog tracking evidence is not considered a novel science needing to undergo a rigorous voir dire as is required by the Mohan test. Second, the court’s use of an alternate test may be more appropriate to qualify dog tracking evidence than the Mohan test, therefore, the Mohan test is unnecessary. It would not be surprising if future cases used the same test in Roy as opposed to the Mohan test when qualifying dog tracking evidence.

The decision in Roy supports the idea that there is a shift in evidence law towards a principled approach. This is shown by the court’s preference for applying principles rather than working with rigid rules. Roy is significant in its analysis of dog tracking evidence. As an appellate level decision, Roy may serve as precedent in cases which depend on dog tracking evidence.


1 R v W(D), [1991] SCR 742.

2 R v Haas, [1962] BCJ No 76 at para 15.

3 R v Mohan, [1994] 2 SCR 9.

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