Can a person be pardoned before being convicted?
A federal pardon can be issued prior to the start of a legal case or inquiry, prior to any indictments being issued, for unspecified offenses, and prior to or after a conviction for a federal crime. … The Supreme Court ruled in United States v. Wilson (1833) that a pardon could be rejected by the convict.
https://en.wikipedia.org/wiki/Federal_pardons_in_the_United_States