David Allen Green, Charon QC, Tim Worstall, Sam Butler and Jerry Hayes have already done a fine job dismantling Paul Staines's arguments for restoring capital punishment (and pointing out the dissonance of hearing such a vociferous campaign in favour from a leading libertarian).
I'll simply and humbly offer one further argument here, courtesy of Al Pacino, playing Lieutenant Vincent Hanna in Heat.
The 1995 film's plot pitches his team of detectives against Bobby (he lets me call him Bobby) De Niro's team of armed robbers. In an early scene, one of De Niro's new recruits goes freelance and unnecessarily shoots the guard of an armoured truck they're knocking over. Within seconds, the second guard and the driver are killed, too.
Hanna arrives on the scene with one of his 'tecs:
You recognize their MO?
HANNAOK. So it's the movies and it's LA and it's squibs and blanks. Of course, the reality of murder is no less abhorrent but far less cinematic than that. But the macabre game theoretic strategy applied by De Niro and his crew was the right one given the options made available to them and the options they understood would be available to the other "players" in the criminal justice system.
Yeah. Their MO is that they are good. Once it escalated into a Murder One beef for all of them after they killed the first two, they popped guard number three 'cause it didn't make any difference anymore, so why leave a living witness? Drop of a hat? They'll rock and roll.
So in a hypothetical circumstance where a victim has already been killed and others are still endangered, could capital punishment be not a deterrent, but potentially an incentive to commit further murders?
I'm happy to accept that such a scenario is so unlikely in reality as to be irrelevant in the formulation of justice policy - and that it is hardly ideal to base such policy on a Michael Mann screenplay.
But wildy extrapolating as I am from the imagination of the creator of Miami Vice, it does highlight how the noose/chair/needle does not really result in the outcomes that its proponents wish.
A better example is the suggestion that in a judicial system based on securing an argument beyond reasonable doubt, jurors are less likely to convict when they might be responsible for the imposition of the death penalty. Perhaps only incrementally so but enough to change the dynamic of our courtrooms.
In the US, the recognition of this has ended up undermining the very concept of trial by jury of one's peers. Thanks to the "death qualification" potential jurors are excluded from hearing capital cases if they are personally opposed to the death penalty:
"Today, in some California trials, that means nearly 40% of prospective jurors are excluded simply because of their qualms about the death penalty...the result of the process is a jury less inclined towards justice and more inclined towards conviction, no matter what the evidence shows."Usually, Guido Fawkes and his supporters are (rightly) the first to rail against the Law of Unintended Consequences, and the ignoring of human nature, when ideological policies trump common sense and evidence. It is odd, to say the least, that this is not the case when dealing with the most important power the State can wield.