Le transfert d'ADN peut se produire de trois façons : innocemment avant le crime, pendant la commission du crime ou innocemment après le crime

R v Hall, 2018 MBCA 122

Lien vers la décision

[194]                  DNA transfer can occur in three ways:  innocently before the crime, during the commission of the crime, or innocently after the crime (see Peter Gill, Misleading DNA Evidence:  Reasons for Miscarriages of Justice (London, UK:  Elsevier, 2014) at 3).

[195]                  The factual matrix rules out the reasonability of an innocent transfer after the shooting.  The gloves and shirt were found soon after at a location with no association to the accused and at a time of day where a transfer of DNA was unlikely before police found the clothing.  There is also no evidence to suggest that, as a result of investigative or laboratory error, the DNA of the accused contaminated the gloves and the shirt through a secondary transfer once the clothing came into the authorities’ control.

[196]                  The difficulty with the alternative of an innocent transfer before the shooting is that it appears to be speculative; particularly as the innocent transfer defence requires the deposit of the accused’s DNA not on one piece of clothing, but on three.  Alternative inferences can arise from the evidence or its absence but an inference must be more than possible; it must be reasonable.  The Crown is not required to negate mere conjecture (see Villaroman at paras 36-37).

[197]                  In R v Doan, 2013 BCCA 123, an innocent DNA transfer defence was raised by way of the argument that the victims’ DNA made its way onto duct tape not because the victims were bound with it, but because of an innocent transfer in the garbage or by police error in handling the exhibits.  The trial judge rejected the reasonableness of that inference.  The Court of Appeal concluded that the trial judge made no error in concluding that the possibility of an accidental transfer was too speculative despite, as here, the trial judge hearing expert evidence on the science of DNA transfer as a general phenomenon (see also R v Abdelhamid (WA), 2015 MBCA 35 at paras 31-32 (where the theory was rejected that the DNA transfer occurred not because of sexual assault, but because of a secondary transfer from a routine medical examination of the victim)).

[198]                  The situation here is even more speculative than Doan, Fitzgerald or Abdelhamid.  The origin of the gloves and shirt before the shooting is unknown.  As previously mentioned, there is no historic connection of the accused to the clothing or obvious innocent association of the accused to the place where the clothing was found.

[199]                  Unlike in Doan, Fitzgerald or Abdelhamid, there are simply no facts (either from the evidence or its absence) to anchor a defence of innocent DNA transfer before the shooting other than the general science.  As was the case in Doan and Abdelhamid, it was open to the jury to reject the general science of DNA transfer as a reasonable inference explaining how the accused’s DNA may have gotten on the gloves and shirt before the shooting.  I would repeat that the probative value of expert evidence is only as good as the facts in the case supporting it (see Abbey, Lavallee and Boucher).  

[200]                  In summary, it was the prerogative of the jury to draw the line between speculative and reasonable inferences.  The role of this Court is not to decide if an alternative way of looking at the case is reasonable enough to raise a doubt, but only to decide if the jury could reasonably have come to the decision they did (see Villaroman at paras 55-56; and Youssef).