The President can only pardon crimes committed under federal law. Most murder convictions take place under state law. However, if the murder was charged as a federal crime, for example based on the murder of a federal agent or a murder taking place on a Native American reservation, the President would be able to use the pardon power in that circumstance.
The full extent of the pardon power has not been tested in the courts. No President has tried to pardon themselves from crimes committed while in office. Therefore, it is not known if the courts would accept this use of the pardon power. However, President Ford issued a pardon to President Nixon over possible crimes connected with Watergate. The court did not determine the legality of that pardon.
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