[KenWittlief]

You cannot not plea bargain your charges down by simply pointing a finger at an innocent man. You would need to have possession of evidence, knowledge of evidence sufficient to convict the other person.

How can you plead guilty to a murder (for example) if you are innocent, and then tell the police where the body is?

Plea bargains are only accepted by the courts when the accused has access to real information and evidence, not just finger pointing.