A subpoena is necessary to compel a witness to testify
In order to compel a witness to testify the government must serve the witness with a subpoena. Without a subpoena a witness is not required to answer any questions.
The Rules Which Apply to Federal Subpoenas
Under federal law, the subpoena must comply with Rule 17 of the Federal Rules of Criminal Procedure and Rule 45 of the Federal Rules of Civil Procedure, which also applies to criminal cases in this regard. The subpoena must be signed by the clerk of the court and sealed usually by embossment. An attorney for a party may obtain blank subpoenas from the clerk and fill in the necessary information and have the subpoena served.The subpoena must indicate the time and place that the witness must appear.
Subpoenas Are Issued for Testimony
A subpoena must be for the witness to testify in a proceeding such as a trial, hearing, deposition or grand jury proceeding. A party may not issue a subpoena for a witness to appear for an interview.
Subpoenas May Be Issued for Documents
Rule 17(c) allows subpoenas to be issued for documents or other objects. The court may allow these subpoenas to produce the information prior to the proceeding. This topic will be discussed in another Guide.
The Rights of the Person Receiving a Subpoena
A subpoena must be reasonable and cannot be "oppressive" or "unreasonable." Rule 45(c) contains provisons for protecting a person receiving a subpoena.
The Court Will Hear Motions to Quash or Modify Subpoenas
If the witness or a party believes that a subpoena is oppressive or unreasonable, they may ask the Court to quash it or modify it. Making a motion does not excuse the witness from complying with the subpoena until and unless the Court acts.
The Right to Remain Silent Does Not Excuse Appearance
While a witness has a right to refuse to testify under the Fifth Amendment to the United States Constitution, that right does not relieve the witness from the obligation to appear as directed by a subpoena which has not been quashed or modified.
Courts Use Contempt Power to Enforce Subpoenas
Under Rule 17(g), a Court may enforce a subpoena against a person who without excuse disobeys a subpoena issued by the Court by holding the witness in contempt.
Consult with Attorney
It is a good idea for any one subpoenaed to testify or even contacted by law enforcement officers to consult with an experienced criminal defense attorney.
THESE COMMENTS ARE NOT LEGAL ADVICE. They are provided for informational purposes only. Actual legal advice can only be provided after consultation by an attorney licensed in your jurisdiction. Answering this question does not create an attorney-client relationship or otherwise require further consultation.