In Toronto Transit Commission (2012), 218 L.A.C. (4th) 260 (Solomatenko), the arbitrator determined that the “collateral fact rule” was not applicable. He explained the rule in the following terms:
The comments by arbitrator Hope in Greater Victoria Drug & Alcohol Rehabilitation Society v. B.C.N.U. (Tataryn) (1998), 71 L.A.C. (4th) 239 (B.C. Arb. Bd.) at p. 260 (as noted in Toronto Transit Commission v. A.T.U., Local 113 (2005), 143 L.A.C. (4th) 123 (Ont. Arb. Bd.) have often been cited for the principle and operation of the collateral fact rule in labour arbitration:
Cross-examination on collateral facts is subject to what is referred to as the “collateral fact rule” which restricts the calling of evidence to prove collateral facts that have been denied. See Sopinka, Lederman and Bryant, The Law of Evidence in Canada (Toronto; Butterworths, 1992), pp. 870-73.
In short, questions put in cross-examination with respect to collateral facts, cannot support an application to call rebuttal or reply evidence to prove facts that have been denied. See Gorsky, Usprich and Brandt, Evidence and Procedure in Canadian Labour Arbitration, 2nd ed., loose-leaf (Toronto, Carswell), at p. 10-43 where the authors wrote in part as follows:
“Collateral Fact Rule”
“The rule provides that a witness’s answer to a question that does not relate to the facts in issue (i.e., something that is merely “collateral” to the issues) is final. The cross-examiner cannot call evidence to contradict it. The credibility of a witness is considered to be a collateral matter.. This is purely a rule of expediency designed to prevent the case bogging down as the hearing wanders off into side alleys to explore matters that are not relevant to the issues. The test as to whether a matter is collateral is whether evidence to prove it would be relevant even if the witness had not been asked about it, in other words, if the only value of the evidence is to contradict the witness’s denial’ it is collateral. Although the problem does not arise often in reported awards, arbitrators have recognized the wisdom of the rule.”
Having regard to the above statements outlining the principle of the collateral fact rule, in my view, the rule simply does not arise in the present situation. The rule speaks to calling evidence to rebut a witness who gave evidence in response to cross-examination on a collateral matter. The union has not even started cross-examining [the employer’s witness] at this point.. The request for the production of the notebook is not a response to a collateral matter. It is a direct response to reply evidence which the employer chose to call. If the union were attempting to introduce evidence to rebut [the employer’s] responses to collateral facts, the collateral fact rule would come into play at that point, but that is not the case in this instance.
The arbitrator ruled that the union was entitled to view the entire notebook from which the two page excerpt was taken.