Me. Rev. Stat. tit. 30-A, § 2678

When a person in custody dies, an examination and inquest must be held, and the chief of police shall cause a medical examiner to be immediately notified for that purpose pursuant to Title 22, section 3025. For purposes of this section, "custody" means custody pursuant to an arrest, confinement in a local lockup or when the person is on the way to or from a courthouse or a local lockup while in the custody of a local law enforcement officer. The medical examiner shall also review the case file and relevant medical records and determine whether an autopsy is needed. If the medical examiner determines that an autopsy is needed, an autopsy must be performed.