Doesn’t high cost just mean there’s an extensive process in place to try to prevent killing innocent people (and yet it still happens). Not sure why that qualifies as “dirty” — wouldn’t killing without the process to save money be dirtier?

Activists against the death penalty raise costs by frivolous litigation and then claim that the death penalty is too expensive. The same thing they've done with other things they don't like, e.g. nuclear power. It's circular logic.

Right, which I might be if it was one in a thousand or maybe even one in a hundred, but even with an insanely lengthy appeals process it's one in twenty or even higher. Not acceptable.

Here you probably mean the innocent wrongfully convicted, but I wonder how an exhaustive appeals process affects the innocent living victims and innocent family members of victims of a rightfully convicted criminal. That they’re forced to relive the trauma of passed crimes again and again every time the death sentence is appealed for over a decade in most cases. It cannot be good for them.

Much better for all involved to reopen a case if and when new evidence of wrongful convictions become convincing enough.