Can an employer rely upon pre-dismissal conduct to justify dismissal?

This would have been so even if the defendant had been unaware of the phone call at the time of the plaintiff's dismissal. It is well established that an employer can rely upon pre-dismissal conduct to justify dismissal even if the employer was unaware of the conduct at the time of the dismissal. This principle can be traced back in Canada to McIntyre v. Hockin (1889), 16 O.A.R. 498 (C.A.), and the comments of Maclennan J.A. (at p. 501): It is now settled law that if a good cause of dismissal really existed, it is immaterial that at the time of dismissal the master did not act or rely upon it, or even did not know of its existence, or that he acted upon some other cause in itself insufficient. The main question always is, were there at the time of the dismissal facts sufficient in law to warrant it …