The death penalty is completely necessary. It has many purposes, all of which are entirely legitimate.
First, it acts as a deterrent to prevent others from committing similar acts of violence. This has not been proven to be effective, but when you think about it, how can it not work? It's easier for someone to kill if they know that their life will be spared. If they know that the punishment will be as harsh as the action, then they will most likely think twice about what they're doing.
Second, it saves the government a HELL of a lot of money that could be used in other beneficial causes such as subsidies, health care, education, or even to give money straight back to the people of the country. I mean, come on, these hardened criminals are being treated like queen's for taking the life of another.
Third, I agree with the theory of "an eye for an eye, a tooth for a tooth." If those *******s can give it they can certainly take it too. I know that if it was me who lost a family member to a murderous scumbag then the last thing I'd want to see is them being pardoned and forgiven.
All in all, bloodthirsty mother ****er's don't deserve to enjoy living when honest individuals die everyday from accidents and disasters.