Luigi Mangione has pleaded guilty to federal charges. What happens now?

Mangione faced two separate criminal prosecutions – in New York state court as well as federal court – over the killing of Thompson.

Though he pleaded guilty Friday in federal court, he still faces eight state charges, including second degree murder. He has pleaded not guilty to all eight of those charges, and he is due to stand trial starting 8 September.

His lawyers have previously argued that Mangione should not be tried in both state and federal court.

But Mangione’s guilty plea in the federal case could have a cascading effect on the upcoming proceedings in state court. It could open the door for defence lawyers to argue the state case runs afoul of double jeopardy – a constitutional protection that prevents an individual from being prosecuted twice for the same crime.

New York’s state constitution has its own prohibition on double jeopardy, which also could have a knock-on effect on Mangione’s upcoming trial.

“If a federal prosecution has been completed on a matter, the state cannot prosecute the matter on those same facts,” said Mitchell Epner, a lawyer and former federal prosecutor.