The government has the right to interrogate anyone with knowledge of the crime who is not protected by some legal privilege. For example, the police can interrogate a medical care practitioner’s employees, but cannot interrogate his wife because the wife is prevented from testifying by a legal rule that is intended to protect marital confidences. In most circumstances, the government would be barred from interrogating someone’s lawyer or a priest who took the defendant’s confession. If a witnesses refuses to cooperate with the investigation, the government can request that a judge hold the witness in contempt of court and punish the witness until he or she testifies.

These witness statements are usually written down, but are not usually provided to the defendant. In federal court, the identities of the government’s witnesses and the content of their statements is protected from discovery by the defendant. This is done to prevent witness tampering and intimidation. If the defendant can convince the judge that identities and statements of the witnesses are vital to the defense, and that there is likelihood of jury tampering, the judge may allow the defendant to know who the witnesses are and what their statements contain. Some prosecutors routinely disclose this information when there is no concern about jury tampering.