I understand what you are saying about wanting something more than life in prison in certain cases but I can no longer bring myself to say that capital punishment is the right answer.
I used to flippantly say things like, at least it prevents repeat offenses, or I'd rather see them dead than have to pay the tax bill to keep them alive. Well, it costs more to kill them than it does to keep them alive and life in prison without possibility of parole prevents repeat offenses too. No matter what reason I came up with for justifying putting someone to death, I found evidence through studies that indicated my position was emotional, not factual.
This is a good link that discusses the cost of the death penalty:
http://www.deathpenaltyinfo.org/article.php?did=108&scid=7
and there are many that discuss the death penalty's failure as a deterrent. This one is from the Amnesty International website:
Quote: Scientific studies have consistently failed to find convincing evidence that the death penalty deters crime more effectively than other punishments. The most recent survey of research findings on the relation between the death penalty and homicide rates, conducted for the United Nations in 1988 and updated in 1996 , concluded: ". . . research has failed to provide scientific proof that executions have a greater deterrent effect than life imprisonment. Such proof is unlikely to be forthcoming. The evidence as a whole still gives no positive support to the deterrent hypothesis".
It is incorrect to assume that people who commit such serious crimes as murder do so after rationally calculating the consequences. Often murders are committed in moments when emotion overcomes reason or under the influence of drugs or alcohol. Some people who commit violent crimes are highly unstable or mentally ill -- the execution of Larry Robison, diagnosed as suffering from paranoid schizophrenia, in the USA on 21 January 2000 is just one such example. In none of these cases can the fear of the death penalty be expected to deter. Moreover, those who do commit premeditated serious crimes may decide to proceed despite the risks in the belief that they will not be caught. The key to deterrence in such cases is to increase the likelihood of detection, arrest and conviction.
The fact that no clear evidence exists to show that the death penalty has a unique deterrent effect points to the futility and danger of relying on the deterrence hypothesis as a basis for public policy on the death penalty. The death penalty is a harsh punishment, but it is not harsh on crime.
http://www.amnestyusa.org/abolish/dp_qa.html
This one summarizes deterrent studies
http://www.deathpenaltyinfo.org/article.php?scid=12&did=167#STUDIES