Credibility refers to the trustworthiness of a witness. If there are different versions of relevant events, the investigator will have to weigh each party’s credibility. Credibility assessments can be critical in determining whether the alleged harassment or violation occurred as many acts may be conducted behind closed doors. Factors to consider include:

Inherent plausibility: Is the testimony believable on its face? Does it make sense?[1],[2],[3]

Consistency of Story and Demeanour: The credibility of interested witnesses, particularly in cases of conflict of evidence, cannot be gauged solely by the test of whether the personal demeanour of the witness carried conviction of truth. The test must reasonably subject his story to an examination of its consistency with the probabilities that surround the currently existing conditions. In short, the real test of the truth of the story of a witness in such case must be its harmony with the preponderance of the probabilities which a practical and informed person would readily recognize as reasonable in that place and those conditions.[4] A witness’s demeanour can be important, but it is a nebulous concept and one that should be approached with caution.[5]

The motive to falsify: Did the person have a reason to lie?1 This may include a person’s interest or bias: For example, did the witness have a vested interest in the outcome of the case or do they evidence bias or prejudice against one party?

Corroboration: Is there witness testimony (such as testimony by eye-witnesses, people who saw the person soon after the alleged incidents, or people who discussed the events with him or her at around the time that they occurred) or physical evidence (such as written documentation) that corroborates the party’s testimony?1,[6],[7],

The weight of the evidence as to a fact does not necessarily depend on the number of witnesses who testify about it.  What is essential is how believable the witnesses are, and how much weight you think their testimony deserves.

Memory plays an important role, but memory can be a false companion. See Taylor Beck’s brief article commenting on Daniel Schacter’s (Harvard) seminal work on memory.

Opportunity and Capacity: Was the person able to perceive, recollect, or communicate about the matter. 2,3,7

Finally, when establishing the weight of the evidence used in investigations, caution must be used in considering the weight of evidence from disreputable and unsavoury witnesses. Consistent with the “Veltrovec Warning,” investigators need to exercise caution in approaching the evidence of certain witnesses whose testimony plays an essential role in the proof of the accused’s guilt.[8]


The following people from the Association of Workplace Investigators were instrumental to the creation of this document: Don Phin, Pam Ring, Rogelio Ruiz, Kristen Hume Scrimshaw, and Karen Sutherland.

© 2018 Falcongate Ltd.

[1] Criteria of the U.S. Equal Employment Opportunity Commission (EEOC)

[2] California Dept of Fair Employment and Housing

[3] 9th Circuit Model Civil Jury Instructions

[4] Faryna v. Chorny, [1952] 2 D.L.R. 354. The British Columbia Court of Appeal noted, at p. 357

[5] G. Anderson, 2016, taken June 2018 from

[6] California Evidence Code 780

[7] California Civil Jury Instructions #107

[8]R. v. Vetrovec [1982] SCJ No. 40; R. v. Sauvé, 2004 CanLII 9054 (ONCA)