Original post by CristocracyNo, because:
1) Not everybody goes around poking others in the eye. Not many do it. In fact, people who do poke others in the eye number as a very small minority. So if I do blind them, the whole world hardly goes blind.
2)Not all stolen property can be returned. What if a thief steals a priceless Rembrandt and irreparably damages it in the process?
Also, it is true that taking a life does not return one, but this in itself is insufficient reason not to impose it. Imprisoning a kidnapper will not make up the time a kidnapped victim loses while being kidnapped; yet it is perfectly just to imprison the kidnapper and take away his time. Ticketing a person speeding also does not make him 'unspeed' as you cannot go back in time to reverse his act of speeding, but we fine him for it nontheless.
3) Luckily for me and unluckily for you, the case study of Singapore exists.
Singapore is a country with extremely harsh punishments, bordering on what some consider brutal. It is also a strong advocate of capital punishment. Yet, Singapore consistently ranks #1 in overall safety, as well as personal safety. Some studies might rank is as #2, but it has always fallen within the #3, usually #1.
So what you just said is factually inaccurate.
However, it is also true that most european countries are safe without capital punishment, but here you are, missing the point again. The point is not that capital punishment is a must to keep states safe. The point is that capital punishment keeps states even safer.
To draw an example: A state without capital punishment has 1 case of homicide for 500,000 citizens (very good)
But a state with capital punishment has only 1 case for every 5,000,000 citizens.
This is an extreme example, but it makes the point perfectly: in the state with capital punishment, 9 more lives are saved, despite them both being very safe countries.
To compare US and Singapore, US is a case where implementation of a good thing (capital punishment) is badly done: needlessly long and complicated appeals, executions happening below the brutalization threshold-thereby causing all the problems Professor Shepard has listed.
Singapore however, is the perfect example of capital punishment done right - a very efficient yet just criminal system, with executions well above the brutalization threshold.
End result? Extremely low crime, extremely low rates of miscarriages of justice (one of the lowest in the world)