in the act; (guilty) without question. We caught her dead to rights with the loot still on her.There he was, bang dead to rights with the smoking gun still in his hands.
In the act of committing an error or crime, red-handed. For example, They caught the burglars dead to rights with the Oriental rugs. This phrase uses to rights in the sense of "at once." [Slang; mid-1800s]