In Hamilton (City), 2013 CanLII 34391 (ON LA) (Surdykowski), the arbitrator set forth the approach to be taken when considering the admissibility of subsequent-event evidence (or in the case of a termination), post-termination evidence.
In that case, the union sought to introduce subsequent-event evidence in the form of psychiatric or psychological assessments of the employee that were undertaken after the employee’s employment was terminated. The grievances were non-disciplinary in nature, in that one focused on the denial of long term disability benefits and the other grieved the employee’s non-disciplinary termination.
The governing law had been set forth in Quebec Cartier,  2 S.C.R. 1095. There, the Supreme Court of Canada adopted a restrictive approach to the admissibility of post-termination evidence. The decision established that post-termination evidence would only be admissible if it shed light on the reasonableness and appropriateness of the dismissal under review at the time it was implemented.
Arbitrators outside of Quebec generally distinguished Quebec Cartier on the basis that their governing legislation, unlike that of Quebec, contained an express provision that permitted an arbitrator to substitute a lesser penalty in a disciplinary matter. They accepted that while Quebec Cartier may be binding in a non-disciplinary matter, that would not be the case where an arbitrator had a statutory discretion to ameliorate a disciplinary penalty.
Arbitrator Surdykowski began his analysis by commenting on the rationale that arbitrators had developed to exclude the operation of the rule in disciplinary matters. After having reviewed the Court’s reasoning in Quebec Cartier and the cases that had interpreted or applied that case, he concluded that the rule remained unaltered from the Court’s original declaration:
The rule remains as stated and consistently applied by the Supreme Court of Canada; namely, that subsequent-event (i.e.post-management decision) evidence is inadmissible for the purposes of determining the justness or reasonableness of the employer decision in issue unless it sheds light on that decision at the time the decision was made and implemented.
Arbitrator Surdykowski then rejected the distinction that arbitrators had created between disciplinary and non-disciplinary cases:
It is clear that in a discipline (including discharge) case the employer cannot use post-discipline/discharge evidence to prove just cause and the union cannot use such evidence to challenge the employer’s decision. To the extent that [some decisions] suggest the admissibility of subsequent-event evidence can depend on the nature of the claim advanced, including a claim of discrimination under the applicable Human Rights Code, I respectfully disagree. There is no reason why as a matter of principle the rule in Quebec Cartier is not equally applicable in non-discipline/discharge cases. Fundamentally the rule is one of relevance, and there is no reason why the test for relevance should depend on the nature of the decision being challenged or the claim being made. It cannot be fair to determine any claim on the basis of subsequent-event evidence which does not speak to the quality of the action or decision in issue.
Arbitrator Surdykowski commented that the Quebec Labour Code (section 100.12 at the time) gave arbitrators the discretion to “set aside the [disciplinary] decision of the employer and … substitute the decision he deems fair and reasonable, taking into account the circumstances concerning the matter.” He then noted that the Quebec Cartier decision appeared to have overlooked that provision.
… as the cases cited in this case demonstrate, Quebec Cartier has not been applied to exclude post-discipline evidence on the issue of substitution of penalty under the Ontario Act. That is, subsequent-event evidence is admissible to demonstrate that it is or is not just and reasonable in all the circumstances for the arbitrator to [use] his discretion under s. 48(17) to substitute a lesser penalty.
Finally, arbitrator Surdykowski concluded that the rule in Quebec Cartier was applicable notwithstanding that there was no discipline component to the grievances. In order for the subsequent-event evidence to be admissible “as arguably relevant, the proposed subsequent-event evidence must ‘shed light on the reasonableness and appropriateness of the [decisions] under review at the time [they were] implemented.’”
The arbitrator stated, in his summative comments, that the issue was really one of relevancy:
To repeat, the issue is really one of relevance. Relevance is determined with reference to the issues identified by the parties in the available “pleadings” and the alleged factual matrix. Evidence that is arguably relevant to the issue (the test for admissibility at arbitration) is admissible.
Although not explicitly stated, the arbitrator`s review of Quebec Cartier can be said to incorporate the following legal principles: