¶1The propriety of allowing a plaintiff, even before the day of trial, to change an action for false imprisonment into an action for malicious prosecution, may be very much doubted ; but to permit a plaintiff, after he had rested his case and had wholly failed to establish it, to amend his complaint, by substituting an entirely distinct and different cause of action, was to take the defendant completely by surprise. He came into court to defend an action against him for false imprisonment, and all that he was required to show, as a complete answer to it, was, what the plaintiff himself established, that the arrest was made *47■upon a warrant granted by a magistrate having jurisdiction. lie may have been, and will be presumed to have been, wholly unprepared to answer the charge, that he was actuated by malice in, or that there was a want of probable cause for, preferring the complaint upon which the warrant issued. To require him, without previous notice, to answer or explain the circumstances relied upon, to show the existence of a want of probable cause, was to deprive him of what he was entitled to, time to prepare and get ready for defending himself against an action which he had no right to anticipate. It was taking him by surprise and giving the plaintiff an undue advantage, and generally to allow a plaintiff, after he has failed in his action, to resort to another, by suffering him to amend his complaint on the spot, would practice be followed by the grossest abuses.
¶2The judge, moreover, erred in telling the jury that the want of probable cause was a mixed question of law and fact. Where there is no dispute as to the facts, which was the case here, it is purely a question of law, upon which the court are bound to instruct the jury positively, and, if they do not follow the instructions they receive, their verdict will be set aside as against evidence. It does not become a mixed question unless there is conflicting testimony as to the facts. Bulkley v. Keteltas, 2 Seld. 384. The judgment must be set aside.
¶3Judgment reversed.