<P> In 1980, after the courts had dismissed their appeals, the Home Secretary, William Whitelaw, used the Royal prerogative of mercy to free David Cooper and Michael McMahon from their imprisonment, both having been convicted of murder on poor evidence . </P> <P> Under the Act of Settlement, a pardon cannot prevent a person from being impeached by Parliament, but a pardon may commute any penalties imposed for the conviction . In England and Wales no person may be pardoned for an offence under Section 11 of the Habeas Corpus Act 1679 (unlawfully transporting prisoners out of England and Wales). </P> <P> In the United States, the pardon power for offences against the United States is granted to the President of the United States under Article II, Section 2 of the United States Constitution which states that the President "shall have power to grant reprieves and pardons for offenses against the United States, except in cases of impeachment". The U.S. Supreme Court has interpreted this language to include the power to grant pardons, conditional pardons, commutations of sentence, conditional commutations of sentence, remissions of fines and forfeitures, respites, and amnesties . </P> <P> The pardon power of the President applies only to convictions under federal law . Additionally the power extends to military court - martial cases, as well as convictions in the Superior Court of the District of Columbia . </P>

Who has the authority to grant a pardon or clemency