Murphy v. Russell
In Murphy v. Russell, 40 Ariz. 109, 9 P.2d 1020 (1932), in the context of a malicious prosecution action, our supreme court laid out in detail the respective roles of the court and the jury in determining probable cause to initiate a prosecution.
It stated, "Whether a given state of facts constitutes probable cause is always a question of law to be determined by the court, and it cannot relieve itself of this burden by casting it upon the jury." Id. at 112, 9 P.2d at 1021.
Rather, the court must "instruct the jurors specifically as to what state of facts will constitute probable cause," and the function of the jury is "to determine what the actual facts were" and "to apply the law as laid down by the court to those facts." Id.