In Cox v. Commonwealth, 227 Va. 324, 329 n.4, 315 S.E.2d 228, 231 n.4 (1984), the defendant "assigned error to the trial court's refusal to issue a subpoena duces tecum requiring the production of certain records of the City Treasurer." Because the bulk of those records had been seized by the police and were in the Commonwealth's custody, the Supreme Court held "they were not subject to a subpoena duces tecum, because they were not in the possession 'of a person not a party' to the proceeding." Id.