Everything you say in your text is correct except the part about 'retards'. Being a retard is not a crime and definitely a retard does not deserve to die.

The biggest problem with the death penalty is that there is no fool-proof mechanism to prevent innocent people from being executed. That's why I prefer life sentencing. Of course, we can make the prisoner do some productive work in prison to off-set the cost of keeping him/her in prison.

My two cents. :)