When we had the death penalty in this country, most killers sentenced to death were in fact reprieved and their sentence commuted to life imprisonment.
The system only wanted to hang “the worst” cases and recognised, even then, that most people (especially people who had killed once only) were capable of reform and redemption. This last idea hasn’t changed.
The average time spent in prison before parole for someone who was reprieved was about 10 years.
When the death penalty was abolished, the trial judge would set recommendations as to how long a life sentenced person should serve before parole was considered, but the decision rested with the Home Secretary.
In the case of the Moors Murderers the trial judge said Brady should never get out and that Hindley should serve 25 years before parole.
Nowadays the minimum period to be served before parole can be considered is set by the trial judge, and in the worst cases life really does mean life.
The minimum periods are often a lot longer now than they were when we had the death penalty.
The relevance of all this to the death penalty debate is that support for the death penalty is actually lower in countries and states where “life without parole” is an option in the worst cases as the public can be sure that the worst killers will never get out.