You searched for: “in flagrante delicto
in flagrante delicto (s) (adverb) (no comparatives)
Descriptive of discovering someone behaving in an illegitimate and unethical way: An in flagrante delicto refers to a legal term which is used to indicate that a criminal has been caught in the act of committing an illegal offense; literally, "with the crime still blazing".

The phrases: "caught red-handed" or "caught in the act" are English equivalents of in flagrante delicto.