Can a sitting U.S. president be imprisoned without impeachment?

Question

A sitting U.S. president can not be indicted for federal crimes as a matter of constitutional separation of powers and DOJ policy, among other reasons.

The president's constitutional protections and powers (e.g., pardon power, etc.) do not extend to the state level. For example, POTUS can pardon people (including himself) on federal crimes. But can not pardon people for state crimes.

Now imagine a scenario where a POTUS, while sitting in office, is indicted by a particular state Attorney General for a crime, say murder, under state statutes. In that scenario, can POTUS be tried, convicted and jailed for those crimes without being impeached?

As a practical matter, could it actually happen? How would it actually play out given the supremacy clause and other practical considerations of jailing the chief federal executive?

Edit

I do not think this question is a duplicate of Can a sitting president of the United States be indicted by one of the states?. That question is limited to the issue of indictment only. This question assumes indictment powers and deals with trial, conviction and, most notably, imprisonment. Given the existing answer to that question, these differences seem relevant and could lead to different or more qualifications on the existing answer.

And, finally and perhaps more importantly, this question also seeks to extract the details of the logistics of how an arrest and/or jailing and imprisonment might or might not be feasible and/or actually occur.

Answer 1

Yes.

In 1872 President Grant was stopped for speeding (on horseback, mind you). The officer, observing that he had stopped the President of the United States, initially let him go with nothing but a verbal warning.

Later the same day, the same officer stopped Grant again speeding in the same place. The officer then informed Grant that he would have to be taken in, to which Grant gave a reply encouraging the officer to do his duty.

Grant was then taken to the police station where he was charged with speeding, and held until he paid a $20 fine, at which point he was released.

In summary, POTUS was:

1. Charged with an offence
2. Deprived of his liberty for committing said offence
3. Held until he served his punishment (paying $20)

... all without impeachment.

Now, this was a long time ago. I think that today, this is unlikely, since Secret Service would (legal or not) shield the President from arrests (national security reasons). However if a state level authority did manage to arrest the President for a crime and refused to let him go, then the Vice President and cabinet would invoke the 25th Amendment (on the grounds that the President is unable to discharge his duties due to imprisonment), so that the imprisoned person would now be a former president.

Answer 2

No one can say with assurance.

The question says:

A sitting U.S. president can not be indicted for federal crimes as a matter of constitutional separation of powers and DOJ policy, ...

The separation of powers issue has never been settled by a court, nor do legal scholars all agree on the point. The DOJ policy is essentially an opinion letter, and any future DOJ could change it. Congress could probably choose to override this policy decision by statute, although it is not likely to do so. Nixon was named as "an unindicted co-conspirator" in the Watergate cases. That is the closest to an indictment of a sitting US President by either state or federal officials, that we have had to date.

If a state accused a sitting president of a crime, whether by indictment or through another process, it is not clear whether a Federal authority would (or legally could) intervene to stop the process. If the state process proceeded, and resulted in a conviction, it is not clear whether federal authority could block sentence from being imposed. No Federal law or constitutional provision that I know of explicitly prohibits such state actions. Members of Congress are explicitly exempt from arrest en route to or while attending a session of Congress, except for "treason, felony, or breach of the peace", but are not exempt from indictment. Most indictments are for felonies in any case, and so would not be barred by that provision even if it were to be extended to the President.