You can spend a long time on the bench (or practicing criminal law) and never have a case in which the defense of provocation is ever raised legitimately.

So, a case from Canada is interesting:

In R. v. PAPPAS, 2013 SCC 56, October 25, 2013, the accused was charged with second degree murder.  The accused shot and killed the deceased, who had been blackmailing him. The accused asked the deceased to stop blackmailing him. The deceased replied by indicating that he had “great fucking insurance.” The accused retrieved a handgun he had brought with him and shot the deceased in the head.

At the accused’s trial, the trial judge charged the jury on the defense of provocation. The jury convicted the accused of second degree murder. A majority of the Alberta Court of Appeal dismissed the appeal.  The accused appealed to the Supreme Court of Canada.

The appeal was dismissed.  The Supreme Court of Canada concluded that there was no air of reality to the defense of provocation and the defense should not have been left to the jury.  The conviction for second degree murder was affirmed.

The Supreme Court held that an air of reality “cannot spring from bare, unsupported assertions by the accused.”  The Court noted that the defense of provocation includes a requirement of “suddenness” which applies to both the act of provocation and the accused’s reaction to it.

In this case, the Supreme Court concluded that the accused knew he would have to kill the deceased to end the extortion.  The element of suddenness was supported by little more than the accused’s “bald assertions that he ‘snapped’ and ‘everything was just automatic.’”