What is the role of a trier of fact in the search for truth?

I consider Justice Saunders’ comments in R v. DDS 2006 NSCA 34: Before leaving the subject and for the sake of future guidance it would be wise to consider what has been said about the trier’s place and responsibility in the search for truth. Centuries of case law remind us that there is no formula with which to uncover deceit or rank credibility. There is no crucible for truth, as if pieces of evidence, a dash of procedure, and a measure of principle mixed together by seasoned judicial stirring will yield proof of veracity. Human nature, common sense and life’s experience are indispensable when assessing creditworthiness, but they cannot be the only guide posts. Demeanour too can be a factor taken into account by the trier of fact when testing the evidence, but standing alone it is hardly determinative. Experience tells us that one of the best tools to determine credibility and reliability is the painstaking, careful and repeated testing of the evidence to see how it stacks up. How does the witness’s account stand in harmony with the other evidence pertaining to it, while applying the appropriate standard of proof in a civil or a criminal case?