In that case a pardon would simply put a stop to the proceedings. Although If one was anal about being judged innocent...

I'm under the impression that a President can issue a pardon at any time for anything and or everything under the sun. Regardless of the current, or lack of current prosecution.

AFAIK Presidents generally wait till the end of their tenure to issue pardons as that tends to make any outrage moot. Slick Willy did that.