Final answer:
A decree that frees an individual from punishment for a crime is known as a pardon.
Step-by-step explanation:
A decree that frees a person from punishment for a crime is called a pardon. A pardon is typically granted by a head of state, such as a president or a governor, and absolves the individual of blame, removing the consequences of the conviction and possibly securing their release from incarceration. It differs from parole or a commutation of sentence, which may reduce the severity of the punishment but does not remove the conviction itself.
In the American legal system, the U.S. Constitution prohibits things like bills of attainder, which convict or punish someone for a crime without a trial, and ex post facto laws, which punish acts that were not illegal when committed or increase the severity of punishment after the fact. The power to grant a pardon is an example of clemency, a broader term encompassing various forms of relief from judgments, including commutations and reprieves.