Idiom
hoist with one's own petard
Theme: HARM
to be harmed or disadvantaged by an action of one's own which was meant to harm someone else; to be revealed as a wrongdoer by being identified with the deed. (From a line in Shakespeare's Hamlet.)She intended to murder her brother but was hoist with her own petard when she ate the poisoned food intended for him.The vandals were hoist with their own petard when they tried to make an emergency call from the pay phone they had broken.