Subpoena translates to "under punishment" in Latin. It is an order from a court for a person to appear at a trial under punishment for failure to appear. If the person given a subpoena does not appear, some courts have the discretion to find the person in contempt of court and either order the person’s arrest or issue fines accordingly.
The term subpoena is primarily used in US courts. The preferred term in the UK is now Witness Summons, at least in civil trials. In either country, the subpoena is usually written by the court clerk after he or she has been given a list of witnesses for a trial. The court clerk then writes out, usually in a form letter, a request for the witness’ presence at a specific date and time for testimony.
When the testimony has lagged or the trial has been delayed, those receiving a subpoena still must appear at the specified date and time. The witness may then be given another date and time to appear, or may have to wait several hours or days to deliver testimony. If one has a time conflict of a serious nature, contacting the court or the attorneys may help change the subpoena date to a better time. In some cases, testimony has been given over long distances, or has taken place in locations other than the court, such as hospitals. In these cases, both the defense and prosecuting lawyer must be present so that fair examination and cross-examination can both take place.
When a subpoena is issued, it is usually the responsibility of the attorney to deliver it. In criminal cases for example, the defense lawyer will deliver subpoenas to any witnesses who might help prove innocence. The prosecuting attorney will deliver subpoenas to those who can help prove the guilt of the accused.
As well, in divorce or child custody hearings, a subpoena can be issued to one of the spouses. Failure to appear in a child custody trial is tantamount to giving up custody of one’s child. Failure to appear in a divorce proceeding tends to mean the divorce is uncontested and may be granted immediately. Financial or custodial arrangements after the divorce usually will favor the appearing spouse.
The US Congress is empowered to send subpoenas when testimony is required in a congressional investigation. The US Congress, like the federal and state courts, can fine people who ignore a summons to testify. A person failing to appear is said to be in contempt of congress.