A few days ago, I wrote a post entitled Assessing Credibility is not a Science. A case crossed my desk today that is the most recent arbitral word on the subject (International Brotherhood of Boilermakers, Local 128 v Procor Limited, 2015 CanLII 4906 (ON LA)). The arbitrator succinctly distilled the Faryna v. Chorny,  2 D.L.R. 354 principles as follows:
Thus, while factors such as demeanor, the ability to recall events and to resist the tug of self interest are important in determining the credibility of a witness, the most significant consideration is the analysis of whose evidence makes the most sense in all of the circumstances. [emphasis added]
That's the update.