What is the test for a jury to prove competent to show deliberation and premeditation in a murder case?

"The necessary elements of deliberation and premeditation may be inferred from all the facts and circumstances as will furnish a reasonable basis for such inferences, and where the evidence is not in law insufficient, the matter is exclusively a question for the trier of fact to determine. [Citations.] Proof of circumstances occurring at the time of the killing, as well as circumstances before and after the killing, are competent to show deliberation and premeditation. [Citations.]" (People v. Mulqueen (1970) 9 Cal.App.3d 532, 544.)