I disagree with the death penalty to an extent. As Jorgi pointed out, mistakes can and have been made. Innocent people have been put to death and later it's come out that they didn't commit the crime. I think that if it's 110% proven that somebody is guilty, then yes they should get the death penalty. Depending on the severity of the crime, of course i.e mass murder etc etc. However, getting life can also be an appropriate punishment. Let them rot in a prison cell, where they will never have any sort of freedom or happiness. After a while a death sentence would probably seem pretty appealing to them.
IMO, life should mean life, with no hope of EVER seeing the outside walls of that prison again. Here in Ireland, and even in the UK, people can be given "life" for the most henious crimes, but be out in say, 10 - 15 years on good behavior. To me that's a total joke.