Circumstantial evidence

R. v. Uhrig, 2012 ONCA 470 is a good source for the proposition it is not individual pieces of evidence but their cumulative effect that maters:

[13]       When arguments are advanced, as here, that individual items of circumstantial evidence are explicable on bases other than guilt, it is essential to keep in mind that it is, after all, the cumulative effect of all the evidence that must satisfy the standard of proof required of the Crown.  Individual items of evidence are links in the chain of ultimate proof: R. v. Morin, [1988] 2 S.C.R. 345, at p. 361. Individual items of evidence are not to be examined separately and in isolation, then cast aside if the ultimate inference sought from their accumulation does not follow from each individual item alone. It may be and very often is the case that items of evidence adduced by the Crown, examined separately, have not a very strong probative value. But all the evidence has to be considered, each item in relation to the others and to the evidence as a whole, and it is all of them taken together that may constitute a proper basis for a conviction: Cote v. The King (1941), 77 C.C.C. 75 (S.C.C.), at p. 76.