Cst. MacDonald’s inability to express the “chances”, i.e. the odds,
of finding artifacts on the appellant’s computer does not mean
that he lacked reasonable grounds. The standard is whether the
authorizing justice of the peace, considering the evidence as
a whole on a common sense, practical and non-technical basis,
and drawing reasonable inferences therefrom, could have reasonably believed that there was evidence to be found at the place to be
searched. The standard to be met is determined qualitatively by
applying reason to the evidence, not quantitatively by attempting
to apply notions based on the probability branch of mathematics.
As Deschamps J. said in R. v. Morelli,  1 S.C.R. 253, 
S.C.J. No. 8, 2010 SCC 8, at para. 129, “[d]etermining whether
evidence gives rise to a ‘credibly-based probability’ does not
involve parsing the facts or assessing them mathematically”
(emphasis added). She approved of the “non-technical, common
sense approach” taken by Rehnquist J. in Illinois v. Gates, 462
U.S. 213 (1983).
 It is essential, as this court said in R. v. Campbell, 
O.J. No. 3767, 2010 ONCA 588, 261 C.C.C. (3d) 1, at para. 54, affd
 2 S.C.R. 549,  S.C.J. No. 32, 2011 SCC 32, “that the
grounds for believing there is evidence in the place to be searched
are based on the operation of reason and not on mere suspicion”.
In determining whether there was a breach of the accused’s constitutional right, the test is “whether there was reliable evidence
in the sworn information before the justice that might reasonably
be believed on the basis of which the justice could have granted
the warrant”: R. v. Manders,  O.J. No. 4757, 2007 ONCA
849, at para. 11.
 The starting point of the assessment of Cst. MacDonald’s
testimony about artifacts is his expertise in cloud computing and
Internet investigations. He had much education, certification and
experience in electronic evidence collection and the forensic
examination of computers. It is significant that throughout his
testimony, he steadfastly maintained he had reasonable grounds
for searching for artifacts. His opinion in a highly technical field
had to be carefully considered and was deserving of weight.
 During his prolonged cross-examination about the chances
of finding artifacts, Cst. MacDonald conceded that the chances he
would find evidence of the actual uploading of the child pornography on the appellant’s physical computer were “most likely
pretty low”. He did clarify that he had grounds to believe the
images were on a thumb drive or other external media. He
reminded counsel of what the ITO he had indicated. The ITO