What is the legal test for knowing possession of a firearm?

In People v. Jurado, supra, 25 Cal.App.3d at page 1031, 102 Cal.Rptr. 498, the jury was not instructed that knowing possession of a weapon was required for conviction of carrying a concealed weapon. The trial court did, however, tell the jury that "[w]here a person intentionally does that which the law declares to be a crime, he is acting with criminal intent...." The Court of Appeal held that said instruction would indicate to a lay juror that the People had to prove knowing possession of the gun. Therefore, failure to expressly instruct on the knowledge requirement was harmless error where the evidence gave no rational basis for finding possession without knowledge.