I also can't accept capital punishment on the basis that the state shouldn't have that power, especially given the proven capacity for human error in the criminal justice system.
What I'm interested in is not to punish criminals but to minimize the number of deaths and suffering in general. I can justify putting criminals in jail because:
1. It protects society from people that threaten it.
2. It allows us to try to rehabilitate the criminal, to convert him into a law abiding citizen for when he's set free.
3. It act as a disincentive for crime.
In the case of a murderer, whether we kill him or we put him in jail for life will protect society against him just as well, and of course, in both cases we don't get to rehabilitate him, so the only question is does capital punishment discourage crime and is it strong enough to offset the cost of their death. Liberals say no and conservatives say yes, but in both cases I don't see much science behind their claim. What I'd like is a systematic study, trying to count every single historical cases of a society establish or banning capital punishment and in every cases see how crime rate has evolved and hopefully find out whether it works or not.
Firstly, why does it matter? We aren't infallible, but death offers no appeal -- I could cite you names that have been falsely convicted of murder but I don't think it's necessary, the point is axiomatic.
As for studies, I don't know what you're talking about. Decades of research has demonstrated that
harsher sentences do not deter others from committing crimes, especially in the United States. This is not an ideological statement; it is based on evidence from numerous studies. The results are quite consistent. The punishment does not sway crime, it is only in the political discourse using public sentiment does this become an accepted truth. Unfortunately, sentiment is king as far as the "tough on crime" politics is concerned, not experts.
I suspect the major impasse is the presumption that criminals rationally believe they're going to be caught (most, in fact, do not), and whether they've considered that the sentence is 2 months or 20 years, or death prior to acting. Deterrence theory assumes rational actors will concede to reason when the possible risk is sufficiently disproportionate to whatever benefit they expect from their action, this has largely yet to be demonstrated with regards to violent crime.
Furthermore, the death penalty (and the criminal justice system in general) is also proven to be systemically racist in the United States (in Canada as well, but the issue is capital punishment).
In the U.S. white offenders who kill white people are lwo times less likely to receive a death sentence than black offenders who kill whites. Black offenders are four times more likely to get a death sentence for killing white people than black offenders who kill black people.
