Where there is doubt then no.
My problems with life in prison are...
Prison can be a living torture chamber, either by guards, other inmates or both. Is that really more humane/moral?
The other is being essentially caged for life and here again is that any more moral or humane than a swift execution?
I'm not saying no one belongs in prison and if the convicted really wanted to live out what passes for a life that way...well then their choice. However, if they opted for death that should be an option that is available as well and not be drug out by third parties filling appeals against it.