Luigi Mangione

Actually, it's arguably a huge prosecution mistake in Magione's favor.

The federal charges were restrained by the circumstances of the event. They couldn't do first or second degree federal homicide, because it didn't meet any of the criteria of those crimes. Of course life without parole is a possibility, but there's high chance that a lesser sentence results.

Knowing the way the state law works, the DOJ probably should have just let the state case play out, where they could have at least gone for second degree murder, with a significant mandatory minimum sentence if convicted.