Under what condition can a subpoena be served by first class mail?

Subpoenas can be served by first-class mail when a certificate of service is provided, as this serves to document that the subpoena has been properly served. The certificate acts as a formal declaration that the individual responsible for serving the subpoena has done so according to legal requirements. This process allows for accountability and transparency, ensuring that the receiving party is aware of the subpoena.

In this context, other conditions, such as personal notification of the witness or sending it to a business address, do not satisfy the specific legal criteria for serving a subpoena by mail. Additionally, including a waiver of service, while potentially relevant in other situations, does not directly pertain to the allowance for mail service unless accompanied by a certificate of service. Thus, the requirement for a certificate ensures that proper procedures are followed, validating the mailing as an acceptable form of service.