Which of the following is not a valid defense in an action for tort?

In tort law, mistake of fact is not a valid defense. Torts are generally based on civil wrongs, and liability arises even if the act was unintentional or based on a mistaken belief. • Volenti non fit injuria: "To a willing person, no injury is done" — valid defense when the plaintiff consents to the risk. • Inevitable accident: An accident that could not have been prevented despite reasonable care. • Act of God: Natural and unforeseeable event beyond human control, like earthquakes or floods. But mistake, even if made in good faith, is not an excuse for a wrongful act.