Only reason I can find against the death penalty is the inability to remedy miscarriages of justice. #hotvote
The reason I can never support the death penalty is that a) even if this were the only reason, it's an important one. Our justice system is not infallible, juries not always unbiased, judges not always privvy to the absolute sum of evidence that may change a sentence. To kill a person is an absolute act that can't be done, and so at the very least we need to be 100% sure the decision to do it is based on completely solid basis...which we can't be sure, ever.
But also b) I value human life. I also value the worth that a human life of an unusual disposition can bring, and that reformation of a person someone would think worthy of the death penalty is a net benefit to society. At best the death penalty is stagnation, given the other option would be to remove the individual from society anyway.
If we have people that are capable of doing things that require the death penalty... serious premeditated murder for example, then they are people we need to understand. Can we gain any more insight in to human psychology and even effects of society on individual behaviour if we simply kill them and be done with it? Why waste such an opportunity purely for retribution?
And of course if you manage to reform the individual, to be confident of their ability to be a positive force in society...even if this is still done from within some level of detention or supervised living...then society has benefited from turning a bad apple in to a good one.
Most support for the death penalty comes from those that are either driven by bloodlust, unable to see that there are no overall benefits to killing a person for their crimes other than for the *potential* temporary good feeling that revenge may or may not bring...or they are those that see these people that are a drain on the state and would rather they weren't, through non-existence.
It's actually the second people I fear the most, as the line between being a drain and a criminal and being a drain and not being a criminal is not very wide at all. But if they have a point it's only because we hamstring our ability to lessen this "drain" by catering too much for the original bloodlusters.
We're too afraid that actually making prisoners productive for society, within the realms of modern human rights, will send the bloodlusters in to a frenzy of outrage...and politicians obviously believe that a significant amount of their electorate are those very type of people.
It just doesn't make logical sense to support the death penalty. We can benefit much more from engaging with criminals, authoritatively and firmly, but humanely...aiming to bring about a net benefit to society regardless of (but especially if) they are rehabilitated. Killing them denies any potential benefit, and results in no better holistic outcome for society than our current system.