Just hang them

I'm not looking for the ultimate punishment. As a non religious person, I don't think that having the worst criminals suffering forever (well, for the rest of their lives) is a good punishment. Getting rid of them is fair enough, removes the risk of them escaping, and saves loads of money which would be better used if they did something to prevent people from becoming murderers, rather than awarding them for it.

Efforts should focus on prevention, however arguing about what the ultimate punishment is is grabbing at the wrong end of the stick. "Punishment" shouldn't even be the point of it. Punishment is just a euphemism for revenge, a hypocritical, evil and barbarous impulse unworthy of human behaviour. We've put a man on the moon and figured out DNA, We are better that that. Rather than revenge, the focus of the corrections system instead should be firstly, to keep the public safe from dangerous criminals, and secondarily to rehabilitate, or at least attempt to rehabilitate the perpetrators of heinous crimes. In all too many cases, Homicide is the result of a serious mental illness( bipolar disorder, depression, schizophrenia) or a societal one (Sociopathology resulting from lifelong exposure to violence inherent in areas of poverty). A society that sanctions the execution criminals by the state is setting a double standard that essentially vindicates homicide and vigilantism. It's sends a brutalizing message to the public that: "Yes, murder is all right and jolly, at least if approved by certain people under certain circumstances."

Note: In practice, execution actually costs the state more money than lifetime incarceration, due to the process of appeals.