What evidence can be relied on to establish frustration?

As to what evidence can be relied on to establish frustration, in Ciszkowski v. Canac Kitchens, 2015 ONSC 73, Archibald J. stated at para. 156: Frustration of an employee’s contract is always established with reference to the time of dismissal. In pleading frustration, an employer is entitled to rely on post-termination evidence not in its possession at the time of dismissal so long as it relates to the nature and extent of an employee’s disability at the time of dismissal. The “evidence subsequently disclosed” should shed light on the nature and extent of the employee’s disability at the time of an employee’s dismissal. An employer is not entitled to rely on evidence that relates to the post-termination nature and extent of an employee’s disability if that evidence is not relevant to the dismissal date. To allow an employer to succeed in pleading frustration on the basis of such evidence would be neither fair nor reasonable.