How many people in prison for crimes far lower than murder have killed prison guards?
With all due respect to Deacon Bresnahan, murderers aren't the only ones who kill prison guards. If he's going to use that argument, then he's also arguing for the execution of thieves, rapists, drug-dealers, and pretty much anyone in a maximum security prison.
I've also never heard a convincing argument that the death penalty doesn't deter criminals.
States such as California (which implements the death penalty) are seeing a horrendous uptick in violent crime between gangs (and sometimes involving innocent bystanders) in the L.A. area. Unless someone runs a Gallup poll of armed robbers and rapists, I don't know how one measures deterrance except by crime statistics, which are going in the opposite direction, if that's the case.
No one is saying that we should execute anyone who might commit a murder. No one is arguing that there is some perfect prediction system where we can take out all potential murderers. All the deacon was pointing out is that known murderers later killed others who might be alive if the murderers had been executed. We don't need to have perfect predictive capabilities. None exist in any case. One can still reasonably argue that capital punishment could have saved the lives of others who were not capital offenders.
And, of course, the real deterrent effect to that kind of crime isn't an impersonal death penalty carried out by the state years later, but a highly personal and immediate death penalty carried out during the crime by a random gun-carrying citizen who gets caught in the crossfire.
When the state stopped trusting the armed citizen and started denigrating his role in crime prevention, it led directly to all of these other problems.
--States such as California (which implements the death penalty) are seeing a horrendous uptick in violent crime between gangs (and sometimes involving innocent bystanders) in the L.A. area.--
Care to back that up with some data?
The problem is, no statistical movement can settle the case either way. We always have to scan a whole range of arguments and data when trying to come to a conclusion about the death penalty.
To definitively prove that the DP deters/doesn't deter murders, we would have to set up parallel universes where all conditions are the same except for the death penalty. You note above that California has the death penalty, but murders are increasing. But the question is, would they have increased more if the death penalty were not in force?
Let's look at it from the other side: in my state, Michigan, we don't have the death penalty. Let's say we institute it and murders drop 15%. Ishmac rejoices and says,"You see, I'm right!" But I would be dumb to claim this as definitive proof because murders may have dropped off for some other reason (eg, all the murderous types left MI because the economy here is tanking and there are fewer people here to rob, beat or kill). Maybe they all move to warmer climes like CA,or better hunting grounds like Chicago, where the death penalty deters some from committing capital crimes--we just don't know. We would have to run our parallel universes and see whether the decrease/increase would have been greater/lesser without the death penalty. So a mere increase or decrease in one direction won't make the case for either one of us, even if the stats seem straightforward.