In this article, the author examines the problems of using legal expertise in the activities of a defense lawyer. Identifies the admissibility of obtaining legal (legal) opinions by a defense lawyer in a criminal case. Determines the expediency of assigning the preparation of legal (legal) opinions to a specialist in the relevant "narrow" field of law. The author argues that the legal (legal) conclusions of a specialist can be used as evidence in a criminal case. As a conclusion, the article formulates a thesis about the need to give legal certainty to the possibility and procedure for using legal opinions (legal expertise) in evidence.