Is there any circumstances that the POTUS can be legally executed within the jurisdiction of the US?

By civil authority, or military authority?

I would guess that since being president does not give them immunity to the law, committing any crime for which the punishment was the death penalty would be a good bet.
Possibly even more so since an example would want to be set

Before or after he was impeached and removed from office?

“As president”, so technically could be after impeachment, but before impeachment sentencing to remove him/her.

As far as state law is concerned, the President is no different from any other citizen.

I’ve speculated before that if a sitting President were arrested and placed in prison, the 25th Amendment would be invoked. It seems pretty obvious that a President would be unable to carry out the duties of his office from inside a cell. The only reason I call it a speculation is because it’s never happened.

Should we discuss the death of a sitting President? Isn’t that treason? And, furthermore, couldn’t he/she pardon themselves?

This is a hypothetical question. No one has mentioned the current President of the U.S. Also, this is not about assassinating the President, but about executing him within the law for any capital crime he might commit.

I’d like the OP to take another shot at this question, research the question a bit, and then have a poignant question for discussion. Until then this is almost Cafe Society.

All State legal systems are separate from the Federal one. If a State has the death penalty, and the POTUS is convicted of a capital crime in a fair trial, then AFAIK there’s nothing that would prevent that State, legally, from executing the POTUS. The POTUS can pardon himself (I believe…) but I think not against State convictions, only Federal convictions.

(Of course practically-speaking, things would never get that far.)

A President might (it’s never been tested) be able to pardon him/herself from federal crimes, but not from state crimes. Of course, it’s never been tested whether a sitting President could even be arrested for either state or federal crimes, so this whole conversation is a Twilight Zone story.

What if he shoots someone on 5th Avenue?

I don’t have a cite, but I’m pretty sure the President can’t be tried or sued while sitting, in order to prevent frivolous lawsuits or trumped up charges from distracting him or her. I’m not sure if this is a federal law or a court decision or maybe just the opinion of the Justice Department’s Office of Legal Counsel.

I know we have lawyers here who can weigh in.

OTOH if the president really did, say, shoot someone on 5th Avenue, I suspect other mechanisms like impeachment would kick in swiftly.

For one thing, it’d be pretty tough to find an unbiased jury when the POTUS is the defendant.

“Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.”

The United States is not a monarchy.

The President can be sued while in office, at least under some circumstances. See Clinton v. Jones.

As I understand it, the President (like many other officials at the federal and state levels) can’t be sued for actions taken as part of the duties of his office. For instance, Bush couldn’t be sued for the Iraq War, because commanding the military is part of the duties of the President. But having an affair isn’t part of the duties of the President, so Clinton could be sued for actions relating to that.

A “poignant” question? Why? And what’s wrong with the question as posed?

As a practical matter there is no way a case could be tried and all appeals exhausted without a president’s term of office ending. Not going to happen in 4 years. Not even 8 years. So unless all appeals are dropped there is no way a president convicted of a capital crime could be executed while in office assuming the crime and conviction occur while in office.

But there is no prohibition preventing a convict already on death row for a previous crime being elected president. Just have to convince the American public and the Electors to give him the job, a tall order. But in that narrow case perhaps a death sentence could be carried out on a sitting president.

Or none of these things. Remind me again who the defendant was in US -v- Nixon?

No death penalty in New York.