How is this any worse than the collateral damage of war?
Capital punishment in it's current form is not a deterrence to crime, it doesn't fix the problems caused by the crimes it is punishing for (it doesn't bring back the murdered, etc), it's more expensive for the state (and therefore taxpayers) than life without parole, and innocents have died at the hands of overzealous police, judges, politicians, and public opinion. So the question then becomes, why do it?
Do you have a source to back that up?
Unlike many other prosecutors in the state, Jackson ... was personally opposed to capital punishment... He also considered it wasteful: because of the expense of litigation and the appeals process, it costs, on average, $2.3 million to execute a prisoner in Texas - about three times the cost of incarcerating someone for forty years.
To play Devil's Advocate: this man was a citizen. A State has fundamentally failed when it has executed one of its citizens.
Imagine a car being hit from the air by a Predator drone because analysis wrongly believes it's full of terrorists. Intended killing. They later realise they made a mistake a killed some family. Now it's unintended killing. Not much of a difference there by my reckoning.
"Broadly defined, collateral damage is unintentional damage or incidental damage affecting facilities, equipment or personnel occurring as a result of military actions directed against targeted enemy forces or facilities."
Source: http://www.fas.org/irp/doddir/usaf/afpam14-210/part20.htm#pa...
If a Predator blows up a car and the family traveling inside it because some intelligence analyst believes it's full of terrorists, that is killing, pure and simple. There's no "collateral" here. If during the same strike, another car with another family is accidently destroyed by the blast, that is, indeed, collateral damage.
To summarize, if you destroy what you're targeting, there's no collateral damage. If you destroy something other than what you're targeting, then there's collateral damage. Collateral damage is unintended killing, but not all unintended killing is collateral damage. Hence, your argument is fallacious.
DoD manual: http://www.dtic.mil/doctrine/jel/new_pubs/jp1_02.pdf
Civilian families aren't lawful military targets.
This guy was collateral damage of the legal system, a (retroactively) unintended killing while we all heartily support the intended ones. The only thing different is the "retroactively" and even then the analogy holds, if the army bombs the wrong people then realises its mistake later.