In general, an exoneration occurs when a person who has been convicted of a crime is officially cleared based on new evidence of innocence.
A more precise definition follows.
Exoneration—A person has been exonerated if he or she was convicted of a crime and later was either: (1) declared to be factually innocent by a government official or agency with the authority to make that declaration; or (2) relieved of all the consequences of the criminal conviction by a government official or body with the authority to take that action. The official action may be: (i) a complete pardon by a governor or other competent authority, whether or not the pardon is designated as based on innocence; (ii) an acquittal of all charges factually related to the crime for which the person was originally convicted; or (iii) a dismissal of all charges related to the crime for which the person was originally convicted, by a court or by a prosecutor with the authority to enter that dismissal. The pardon, acquittal, or dismissal must have been the result, at least in part, of evidence of innocence that either (i) was not presented at the trial at which the person was convicted; or (ii) if the person pled guilty, was not known to the defendant, the defense attorney and the court at the time the plea was entered. The evidence of innocence need not be an explicit basis for the official action that exonerated the person.
Exoneree—A person who was convicted of a crime and later officially declared innocent of that crime, or relieved of all legal consequences of the conviction because evidence of innocence that was not presented at trial required reconsideration of the case.
Arson Case—the exoneree was convicted of arson, or the exoneration depended at least in part on evidence that the exoneree did not commit arson.
Child Sex abuse Hysteria (CSH)—A case in which the exoneree was convicted of child sex abuse as part of a wave of child sex abuse prosecutions in the 1980s and 1990s based on aggressive and suggestive interviews of children who were thought to be victims. These cases generally included bizarre and implausible claims by the supposed victims, frequently featuring satanic rituals.
Co-Defendant Confessed (CDC)—A codefendant of the exoneree, or a person who might have been charged as a codefendant, gave a confession that also implicated the exoneree.
False Confession (FC)—The exoneree falsely confessed if (1) he or she made a false statement to authorities which was treated as a confession, (2) the authorities claimed that the exoneree made such a statement but the exoneree denied it, or (3) the exoneree made a statement that was not an admission of guilt, but was misinterpreted as such by the authorities.
False or Misleading Forensic Evidence (F/MFE)—Exoneree's conviction was based at least in part on forensic information that was (1) caused by errors in forensic testing, (2) based on unreliable or unproven methods, (3) expressed with exaggerated and misleading confidence, or (4) fraudulent.
Inadequate Legal Defense (ILD)—The exonoree's lawyer at trial or on appeal provided obviously and grossly inadequate representation.
Mistaken Witness Identification (MWID)—At least one witness mistakenly identified the exoneree as a person the witness saw commit the crime.
No Crime (NC)—The exoneree was convicted of a crime that did not occur, either because an accident or a suicide was mistaken for a crime, or because the exoneree was accused of a fabricated crime that never happened.
Official Misconduct (OM)—Police, prosecutors, or other government officials significantly abused their authority or the judicial process in a manner that contributed to the exoneree's conviction.
Perjury or False Accusation (P/FA)—A person other than the exoneree falsely accused the exoneree of committing the crime for which the exoneree was later exonerated, either in sworn testimony or otherwise.
Posthumous exoneration (PH)—An exoneration of a person after that person died, including cases in which a living codefendant was exonerated under circumstances that clearly indicate that the deceased person would have been exonerated if he or she were alive.
Shaken Baby Syndrome (SBS)—The exoneree was convicted of injuring or killing an infant by violent shaking, based on a medical diagnosis that is now highly controversial.