I'm against capital punishment, for the simple reason that there is always the possibility, however remote, that you will end up executing an innocent person. I also have personal moral objections to it, but tend to avoid debate in that realm, as there are strong moral arguments for both sides of the debate.
The only possible benefit that I can see resulting from capital punishment is saving money (ie. we don't have to spend money to house/feed a prisoner). Capital punishment does not serve as a deterrent. The U.S., which practices capital punishment, actually has higher crime rates than many countries that don't; and numerous studies have shown no correlation between capital punishment and decreased crime.
The only other argument to justify capital punishment is that of punishment, inflicting a punishment on the offender that is 'equal' to the crime they committed.
I have severe moral objections to any argument that seeks to justify killing other humans simply to save money. And while I agree wholeheartedly with the concept of punishing criminals, I do not think that killing them is the best way, in light of my initial note that it is possible that we will end up killing an innocent person.
Now, don't slap me with the label of "bleed heart liberal" here. I am a very staunch proponent of strict sentencing for criminals. I would have no objection whatsoever to putting murderers, rapists, etc., into prison for the rest of their lives. While the principle of "reforming" them is a great one in principle, there are too many of these offenders who released into the public, only to commit the same offenses again. And while I do sympathize with arguments for a prisoner's right to reform themselves and regain their freedom, I sympathize even more with the rights of a regular citizen to be protected from the risk presented by such people.
Regarding the cost issue, I do agree with concerns about the costs to house these prisoners. The amount of money spent annually to support a convicted felon is far higher than the amount of money spent annually to help a jobless single mother with two children. Is that not a basic injustice in and of itself?
So I'd personally support a prison system in which all prisoners did get very basic 'rights' (that is, the state provides enough food, clothing, etc., for them to live on), but that for anything else, they must work and make money for themselves. And I have no problem whatsoever with the idea of using prison labor to produce commercial products; while it can lead to abuse, with suitable laws and monitoring in place, prison factories need be no different than any other factory.
To summarize: A person is convicted of first degree murder, or rape. Put them in prison for the rest of their lives, without hope for parole or early release. Make them work, and provide money both for themselves, and to support the prison system, so that more taxpayers' money may be directed in other directions.