The totality of the evidence must prove beyond a reasonable doubt. But not every piece of evidence must provide beyond a reasonable doubt. If all you have is

The totality of the evidence must prove beyond a reasonable doubt. But not every piece of evidence must provide beyond a reasonable doubt. If all you have is a finger print--then yea--the possibility someone else with a close match did creates reasonable doubt. But if the thief was seen in the area at the time and you have a finger print, well that's less reasonable now. TL;DR; apply Bayesian probability.