It’s one of those things that would greatly depend on the specific circumstances. As I mentioned the courts do allow for jailhouse confessions. The witness is acting as and agent of the state. The witness does get compensated for his actions. The defendant is in custody. The admission would be allowed in court. It would probably come down to a good faith/bad faith argument. If the police are acting in bad faith to get around his rights it won’t be allowed.
Don’t assume that. The state could charge a person with both crimes if the facts fit.
The state? Your whole sick society. That’s who’s guilty, man. We’re just your lousy escape goat. Besides, man, who the hell cares?
Summary
Call back to the punk rock episode mentioned in the OP.
He could be charged with murder. Statute of limitations could be used to dismiss the charge or a conviction but if a court allows a trial to move forward based on a murder charge then it’s ruling that it is murder.
Varies by state as usual. In Utah there is no limit for manslaughter.
The killer caught up with Quincy while the Big Q was nailing down evidence. The discussion quoted above was done while the killer was holding Quincy at gunpoint, and Quincy didn’t ask any questions until after the killer admitted to the murder.
The rest of the body was scattered during the construction work that revealed the femur.
There’s some other circumstantial evidence (independent of the confession): the killer provided a different body in sealed in a coffin to the father of the victim and provided a fake story about the death. There’s also his actions in the present - trying to harm the people investigating the body implies a motive to do so.
Many times a jailhouse informant, if it is the major part of the case against someone, indicates the state does not have much of a case - particularly if the informant is deliberately placed with the accused to get “proof” he’s guilty.
How does that work? Can a person be found guilty of both felony murder and murder, or are they essentially the same crime? Can a person be guilty of, for example, murder and manslaughter for the same act? What makes two charges for the same act mutually exclusive? Or would the jury be given an option “pick one”?
They can be charged with both - but that doesn’t necessarily mean they can be convicted or sentenced on both. You cannot be punished twice for the same offense in the US - but you can be charged with multiple counts for the same offense. In fact, it happens all the time that someone is charged with both murder and manslaughter or attempted murder and some form of assault/battery - but there will ultimately be a single sentence if one crime is a lesser included offense of the other.
The felony murder rule doesn’t apply to completed crimes. If the killer and his partner had reached a place of safety and we in the process of calmly discussing what to do with the loot, the underlying robbery was complete and the murder didn’t occur during the commission of the felony.