No a killer cannot just plead guilty and give no information at all IF they are taking a PLEA DEAL. The prosecution can require a complete proffer (testimony) of the crime in order for the defendant to get their plea deal.
Prosecutors normally want a FULL CONFESSION from the defendant that details how they carried out their crime.
For example, the prosecution not giving a plea deal unless the killer reveals where they buried the body, or where they disposed of the weapon, or how were they able to gain access to the victim's home? The prosecution can even interrogate the defendant as to their motive etc...The prosecution has the upper hand in any plea negotiation.
The confession and proffer can be used as leverage. "You give us a full confession of your participation and planning in this crime and help bring closure to the families, and we in
exchange will give you the plea deal you want." Plea deals are an
exchange, the defendant gives something and in exchange the prosecution gives something in return - the net result of this is almost always a lighter reduced sentence.
But if the defendant wants to plead guilty WITHOUT A PLEA DEAL, this is when you may get zero answers.
Without the plea deal the prosecution loses their leverage and can't demand a full confession and full proffer. They can ask, but a stubborn defendant who has no remorse and doesn't care about giving the family some closure won't give the answers.
Some say we need the death penalty to secure confessions and plea deals to get life without parole. But this isn't necessarily the case.
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