An acquittal is a release of a criminal defendant from the charges against him. The determination can be made by a judge or jury, or can also be made by the prosecutor if he or she decides that the case should not go forward. For example, at O.J. Simpson's murder trial, his criminal defense lawyer repeatedly referred to a glove found at the crime scene, highlighting the weakness of the prosecution's case by stating, “If it doesn't fit, you must acquit!” After an acquittal, the constitutional prohibition against Double Jeopardy prohibits further prosecution of the defendant for the same crime, even if new evidence is discovered. Additionally, an acquittal can not be appealed except for under one rare exception (see, Harry Aleman v. Judges of the Criminal Division, Circuit Court of Cook County, Illinois, et al., 138 F.3d 302 (7th Cir. 1998), where the court held that Double Jeopardy does not apply when a defendant is acquitted by a bribed judge – in other words, under those circumstances, a defendant can be reprosecuted. An acquittal does not prohibit the filing of a civil action against the defendant on the same set of facts. For example, after O.J. Simpson was tried and acquitted for murder, the families of the murder victims successfully sued him in civil court for Wrongful Death.
Acquit also means to release a person from a contractual obligation (particularly a financial obligation.) For example, when you give a person a receipt for payment, you have acquitted his or her financial obligation to you.