Personally I think it is unfair handing out the death penalty because that person knows generally speaking that they are going to die at a certain date.
Myself and most of us we have no idea when we are going to expire.That really is unfair what if you are to live to 95 but you do not know this until you turn 95 so you lived a hard live and punished your body now you are a 95 year old man more or less in agony with creaky knees.Had you have known you would see your 95th birthday you'd have taken a truckload of Omega 3 fish oil and eaten a few less Whoppers or married a less annoying woman.
Or say that you are going to expire at 35 years of age if you knew this you could enjoy life to it fullest and party every day and not bother with long term plans.
I am being sarcastic.
In all seriousness I think a life trapped in a cell is worse than a set date to die.What is really worse 10 years or so on death row but then you die or life in prison to ponder what will happen to your soul when you do die.Or for an atheist a lifetime rotting away in a cell not being able to enjoy the life that you have that will end in nothingness when you die.
I do not see the death sentence as a deterrent either many people have been put to death yet still many people commit crimes that carry death as a possible punishment.