Coram nobis is a legal term for a writ produced by a court to vacate the outcome of a case when a clear mistake of fact occurred. If it is not possible to vacate the outcome in the original case, it may be modified with a writ of coram nobis. Such writs are relatively rare and they may be applied in different ways, depending on the jurisdiction. In some regions, for example, it is not possible to use this type of legal writ in a civil case, only criminal cases.
A petitioner requesting a writ of coram nobis must be able to show the mistake of fact and explain why it was not addressed at the time. Mistakes of fact can occur for a variety of reasons, ranging from an innocent unawareness about a fact to a prosecutor's decision to withhold exculpatory material from the attorneys on the defendant's side. Cases where people were intimidated or misled into withholding facts can also be used as ground for this type of legal writ.
People may find out about a mistake of fact long after a trial is over, or may have other reasons for delaying the move to seek a legal remedy at the time the mistake is discovered. Generally, explaining why there was a delay can be one of the most difficult parts about requesting a writ of coram nobis. In cases where information was clearly withheld and people just discovered it, the writ can be more clear-cut, but in others, a judge may view the request for a writ of coram nobis unfavorably.
Sometimes, such writs do not go through until after a case has been decided and someone has been penalized. In the case of people released from prison after serving a sentence, this type of writ can be used to restore the ex-prisoner to the pre-conviction state, restoring voting rights, ending parole restrictions, and addressing any other restrictions placed on the person as part of the sentence or terms of probation. In civil cases, the writ can be used to throw out a judgment ordering someone to pay damages or to end an injunction.
An attorney can prepare a petition for a writ of coram nobis, going over the reasons the writ is being requested and providing supporting material. The rarity of this type of legal writ means that an attorney may not be very familiar with the process, and some research may be necessary to draft the most effective and useful petition.