Mistake means when one commits an error in understanding or when one understands or perceives wrongly.
Mistake may be of two kinds—(a) Mistake of fact, and (b) Mistake of law. Mistake whether of fact or of law, is generally no defence to an action for tort. When a person willfully interferes with the rights of another person it is no defence to say that he had honestly believed that there was some justification for the same, when, in fact no such justification existed.
But the general rule stated above is subject to certain exceptions provided the defendant acts reasonably. Wherever malice or a wrongful motive has to be proved by the plaintiff, mistake will furnish a good defence. For example, for the wrong of malicious prosecution it is necessary that the defendant had acted maliciously and without reasonable cause and if the prosecution of an innocent man is mistaken it is not actionable.