What is the test for determining probable cause in a civil case?

People v. Paul, 147 Cal.App.2d 609, 619, 305 P.2d 996, 1002: 'Appellant concedes that as a general proposition of law, 'it is correct to state that probable cause is a question of law to be decided by the trial court rather than the jury', but contends, and rightly so, that this rule is applicable only where there is no conflict to be decided by the court. [citations] As was said by this court in Aitkin v. White, supra, 93 Cal.App.2d at page 141, 208 P.2d at page 791: 'When the facts are controverted or the evidence conflicting, then the determination of their legal effect by the court is necessarily hypothetical, and the jury are to be told that if they find the facts in a designated way, then such facts do or do not amount to probable cause. (Citing cases.)' * * *