I am against the death penalty for many of the reasons already stated.
However, I am fervently in favour of life meaning life in a 4ft x 4ft cell with constant artificial light, no interaction with anybody, the barest of rations just to keep them alive and being made to wallow in the own filth.
This, to me, is worse than death and is a greater deterrent than the death penalty could every possibly hope to be.
Make their life a living hell.
Obviously this would only be for the most heinous of crimes, the Chindamos, Sweelings, Huntleys and Paines of the world.
And while I'm here, the hackneyed 'the death penalty makes us as bad as them' or 'makes us murderers' is just about the single most ridiculous argument against the death penalty there is.