From The Art and Popular Culture Encyclopedia
A pardon is the forgiveness of a crime and the cancellation of the relevant penalty; it is usually granted by a head of state (such as a monarch or president) or by acts of a parliament or a religious authority. Clemency means the forgiveness of a crime or the cancellation (in whole or in part) of the penalty associated with it. It is a general concept that encompasses several related procedures: pardoning, commutation, remission and reprieves. Commutation or remission is the lessening of a penalty without forgiveness for the crime; the beneficiary is still considered guilty of the offense. A reprieve is the postponement of punishment, often with a view to a pardon or other review of the sentence (such as when the reprieving authority has no power to grant an immediate pardon).
Today, pardons are granted in many countries when individuals have demonstrated that they have fulfilled their debt to society, or are otherwise considered to be deserving. Pardons are sometimes offered to persons who are wrongfully convicted or claim they have been wrongfully convicted. Some believe accepting such a pardon implicitly constitutes an admission of guilt as a pardon does not set aside the conviction, so in some cases the offer is refused. Cases of wrongful conviction are nowadays more often dealt with by appeal than by pardon however, a pardon is sometimes offered when innocence is undisputed to avoid the costs of a retrial. Clemency plays a very important role when capital punishment is applied.