In what circumstances will a defendant be found guilty of the attempted murder of a police officer while carrying nitroglycerin?

In Kauffman, the defendant and six friends planned to break into a safe at a cemetery. Armed with guns, a bottle of nitroglycerin (to blow open the safe), and burglary tools, they went to the cemetery, where they found an armed guard by the safe. They turned back. On their way home, an encounter with a police officer led to a gunfight in which the officer was killed. The defendant, who had been carrying the nitroglycerin, was unarmed and did not participate in the shooting, but he was charged with and convicted of the officer's murder. (People v. Kauffman, supra, 152 Cal. at pp. 332-334, 92 P. 861.) On appeal, the defendant argued that the evidence was insufficient to support his conviction.