Originally Posted by
MadMojoMonkey
1) Yeah. Impeachment is equivalent to a Grand Jury. If the impeachment hearing reaches a supermajority of votes to impeach, that amounts to a criminal indictment. That is, the impeachment hearing is a precursor to leveling criminal charges and any legal actions that follow. The purpose is to see if there is adequate evidence to take the time and effort to press charges, basically. It's meant to protect elected officials from frivolous law suits, as I understand it. IF the impeachment goes through, then removal from office to stand trial is the next legal action.
It should be noted that 2 US presidents have been impeached and neither left office.
Nixon was not impeached, but resigned when it became clear that he would be impeached. Nixon was pardoned by Ford, even though at first Ford said he'd only do it if Nixon apologized. Nixon said he didn't commit any crimes and had nothing to apologize for. Ford relented and pardoned him anyway.
4) That was a rabbit hole.
As far as I can tell, impeachment only applies to "officers of the US federal gov't." This includes not just POTUS, but top-level federal judiciary seats and all offices which are filled by presidential appointment with Senate approval.
In addition, it includes every officer in all branches of US military. I assume impeachment doesn't apply to military officers, as the military has its own courts, but it's a guess.
So, as far as I can tell, once the official is no longer in office, the impeachment clause does not apply to them. That's under the assumption that "officer of the US fed gov't" isn't a lifetime title, but that's not completely clear. A person may choose to hold the honorific "The honorable" [MMM] for life, having ever held one of these offices, though wikipedia says use of this honorific is not common.
I'm not exactly sure who and under what circumstances needs to be impeached to continue with criminal prosecution, and an ex-POTUS may or may not have that protection.