I find this post quite confusing.

I don't see any support in it for the assertion that we might want to keep someone alive indefinitely just because his crime was so evil. You have only described the value of extracting certain specialized knowledge that he might have. This is not the same thing (although there is some psychological and historical value that might corrolate with this).

But, surely, this is only a reason to keep him alive temporarily. At some point, we're unlikely to get anything more useful from him than from a typical murderer.

And choosing to not execute some because we might not execute others as quickly doesn't make any sense to me. We want to treat people fairly, not equally. If one person deserves execution, then another person's treatment should be irrelevant.

I expected The World's reason to avoid executions to have something to do with our fallibility and the moral horror of executing the innocent.