X' sees 'Z' committing what appears to 'X' to be a murder. 'X', in exercise, to the best of his judgement, exerted in good faith, of the powers, which the law gives to all persons of apprehending murderers in the act, 'seizes 'Z', in order to bring 'Z' before propel authorities. But it turns out that 'Z' was acting in exercise of his right of self defence. 'X' is guilty of: