Coffin v. Superintendent, Massachusetts Treatment Center

General Laws c. 123A, § 12 (b) (§ 12 [b]), permits the Commonwealth to file a petition to commit a person as a “sexually dangerous person” (SDP) only if the person is a “prisoner or youth in the custody of the department of youth services.” This case requires that we decide whether, for purposes of § 12 (b), a person placed in custody pursuant to an unconstitutional statute is nevertheless a “prisoner” within the meaning of the statute. At the time the Commonwealth filed its petition for *187commitment of the plaintiff as an SDP, he was incarcerated solely for violating the conditions of lifetime…