Earlier quoted context omitted.
In all of the mistrials and cases where innocent people have been killed, someone has thought the party was guilty. The thing that makes the death penalty barbaric is that people have misplaced confidence in their opinions.
There are two issues here that most commentary about this case seems to be happy to conflate: - Is he guilty - Should he be executed These are independent questions. One is a question of fact, and there seems to be almost no credible reason to doubt his guilt. The other is a question of ethics and policy. As for your argument on why the death penalty is barbaric, it is not a valid argument. Reductio ad absurdum, your…
For example, suppose you have a family friend, Randall, who is accused of being a child molester. If you are perhaps 5% certain that Randall is a child molester, you would be justified in not letting your children stay at his house unattended. Just to be safe. If you are 51% certain that Randall is a child molester, that's more certain than not, but 49% is still "reasonable doubt". Ok, let's say we're about 90% certain Randall is a child molester, which is probably enough to get a jury to convict. 1 out of 10 times, that's a false conviction, but that's ok because people can be released from prison and dropped from the sex offender registry if it turns out they were innocent. Let's suppose, for the sake of argument, that we agree that child molesters should get the death penalty. What level of certainty is needed before we kill Randall? Surely more than 90%, or else 1 out of 10 people we kill will be innocent, and while that's an acceptable margin for imprisonment, it's probably not good enough for doing something completely final and irreversible. So does the level of certainty have to be 99%--so that 1 in 100 executed inmates is innocent? 99.9%--perhaps 1 out of 1000 is a more palatable rate of innocent people being executed? 99.99% then?
The question isn't whether someone is guilty, the question is whether we are confident enough in his guilt to take the risk of killing an innocent man. "Is he guilty?" isn't a binary question of fact, it's a question of certainty and implicit in that question of certainty is the acceptance of killing some innocent people as well.
The more nines we need to kill someone, the fewer people are left as candidates for the death penalty. Getting those nines means an exponential increase in legal costs. It also means spreading the fixed costs of execution infrastructure over a smaller number of executions. At some point, either you have to stomach a lot of innocent people being executed or the death penalty just becomes completely impractical, even if you start from the assumption that it's morally justified.