Capital Punishment Mad Fool,
In your opening post you claimed that the justice, by definition, requires fairness. Fairness, you said was the principle that "all are equal before the law, similar offences will be treated similarly". Fairness, as a legal principle is grounded in the presumption that all men are created equal. The problem is that al men are not created equal. For example, there is a robust body of research evidence suggesting that psychopaths have, amongst other abnormalities, a deficit of empathy which manifests itself a in callous, cold-hearted, remorseless behavioural traits. This empathetic deficit is believed to be biologically based in the frontal lobe ( prefrontal cortex) of the human brain .Neuroimaging studies of convicted , incarcerated homicidal psychopaths show that there are some broadly common neurobiological structural and functional abnormalities in the prefrontal vortices of these individuals. My point is, that if a person has an organic ( biological) abnormality in the prefrontal cortex of their brain that strips them of any sense of empathy, remorse ,sympathy, or conscience for the commission of a brutal premeditated murder where their victim has been, say, raped, then tortured before being killed, then this is not just "murder one". The killer, because s/he is biologically abnormal is incorrigible, and having no sense of regret or remorse for their action/s is very likely to continue murdering others in the same fashion if they are ever at liberty to do so. What is the point of sentencing such a person to "life" (25-30 years or whatever) in a high-security prison, at the tax-payer's expense, if they incapable of being rehabilitated? Why should the state not execute them in the interest of bettering society by diverting the (considerable) costs of incarcerating such an individual to help provide revenue for improving public health or education, etc?
So, in short, your presumption that the legal principle of fairness is: "Perfect, at least on paper. Not much controversy in it." is, in my opinion false. All human beings are not created equal, they are all biologically different from each other, and in the case of sadistic homocidal psychopaths is a pertinent example wrt your op. Such individuals ( the American serial killer, Ted Bundy,is a good example), if apprehended and convicted, ought, in my opinion, be executed by the state for the reasons I have outlined above. If you disagree, please explain your objections.
Regards
John