What is the test for a jury to convict a defendant who "exploded" at the time of the murder?

The People also argue the fact that defendant "exploded" does not mean he did not act with deliberation, and cite cases in which premeditation and deliberation were found sufficient to support a first degree murder conviction, despite evidence that the defendant erupted at the time of the killing. (See People v. Wharton (1991) 53 Cal.3d 522; People v. Koontz, supra, 27 Cal.4th 1041.) These cases are inapposite because they did not involve the circumstances that existed here, namely a defendant who said he contemplated killing himself, his ultimate victim, or both of them in the hours preceding the murder, and ultimately fixed on killing himself, only to suddenly explode and kill his victim after she made comments that emotionally upset him.