A court-backed order to give evidence or hand over documents - enforceable against people who are not parties to the case at all.
A subpoena is a command, issued under a court's authority, requiring a person to do one of two things: attend and give testimony, or produce documents and records. Its distinctive quality is reach. Most orders in a lawsuit bind the parties; a subpoena binds strangers to the dispute - an employer, a bank, a doctor, a phone company, a witness who saw the collision - and that is exactly why the rules surrounding it are protective.
Two forms exist and are often combined. One requires a person to appear and testify, at a deposition, a hearing or a trial. The other requires production of documents or things, and in that form the recipient can frequently satisfy it by sending the records without appearing at all. In most systems a lawyer may issue a subpoena in the court's name without asking a judge first, which is a considerable power and the reason the objection routes below exist.
A subpoena is not simply to be obeyed to the letter, and this is the part most often misunderstood by recipients. It can be objected to or challenged - by written objection to the party who issued it, or by asking the court to quash or modify it. Recognised grounds include that compliance would be unreasonably burdensome, that it requires travel beyond the geographic limit the rules allow, that it seeks privileged material such as communications with a lawyer, or that it demands sensitive records without adequate protection. Courts routinely narrow subpoenas rather than enforcing or cancelling them outright.
Ignoring one is the one response with no upside. Non-compliance without objecting or moving to quash can be treated as contempt of court. The distinction that matters is between challenging a subpoena, which is legitimate and expected, and disregarding it, which is not.
The common situation is receiving one when you are not part of the case - and a short consultation is worth far more here than its cost, because the recipient usually has more room to object than they realise and a very short window in which to do it. It matters most where the material is privileged, where it belongs to someone else such as a patient or a client, or where producing it could expose you to liability of your own. If a subpoena arrives concerning records about a third party, tell that person: they may have a right to object that you do not.
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