Final answer:
A valid subpoena duces tecum for health records must be served on the custodian of the records, specify the records, and be issued by a court, but it does not have to be signed by a judge.
Step-by-step explanation:
A valid subpoena duces tecum seeking health records has specific requirements it must meet to be enforceable, except for one. Notably, it does not necessarily have to be signed by a judge. However, it must be served on the custodian of the records, specify the records being sought, and be issued by a court to be considered valid. A judge's signature is not always a requirement, as subpoenas can also be issued by a court clerk or an attorney involved in the case in many jurisdictions.