Which document requires service on a witness to testify?

• A. Writ of Attachment
• B. Proof of Service
• C. Subpoena Ad Testificandum
• D. Affidavit of Service

Answer: (C)

A subpoena ad testificandum is the instrument that commands a person to testify. It becomes enforceable only after it is properly served on the witness, which provides legal notice and a basis for court enforcement if the witness fails to appear. This service requirement ensures due process and that the witness cannot be compelled to attend without proper notice. The other documents do not compel testimony: a writ of attachment relates to seizing property to secure a judgment; a proof of service simply records that service occurred; an affidavit of service is the server’s sworn statement about how and when service was made.