Life without parole
It is one thing for a person to confess freely to a crime and quite another for someone to be convicted on the available evidence without a confession.
Confessions themselves can be controversial. Many times, a person is subjected to questioning techinques that border on coersion and then various statements they make are strung together and presented as a "confession".
As for the possibility of rehabilitation in prison, that is questionable at best in the United States. The prison environment is one of absolute hate, violence, and fear. Ho can any person be reasonably expected to make meaningful positive changes in such an environment over the course of 20 years? He/She would have to have a tremdous desire and will in order to come out of that situation a better person. It is not impossible and has been done but it is very difficult.
The whole issue of crime and punishment or crime and rehabilitation is complex. I have theories on how to accomplish an aalomost total personality change in convicts but with the current attitude toward things, they would not ever be allowed.

