Which of the following is a requirement for serving a subpoena?

Serving a subpoena requires that the individual executing the service is at least 18 years old. This age requirement ensures that the person is legally an adult and capable of understanding the responsibilities associated with serving legal documents. In many jurisdictions, including Maricopa County, there are specific rules that regulate who can serve subpoenas, and typically, any competent adult is allowed to perform this task.

The other options have specific limitations or requirements that are not universally applicable. For instance, a party to a case may serve a subpoena, but this is not a blanket requirement because non-parties can also serve. Similarly, an attorney can indeed serve subpoenas, but this is not a condition that restricts service solely to attorneys. The requirement that the subpoena must be filed with the court before serving is also not universally applicable, as subpoenas can often be issued and served without prior filing, depending on the circumstances. Thus, the emphasis on the age requirement for anyone serving a subpoena captures a fundamental aspect of legal procedure.