Eternal punishment update

This Aeon interview with philosopher Rebecca Roache on the (future) possibility and ethics of extending prisoners' lifespans so they can be punished more has gotten some attention (I was one who tweeted it) and some controversy. I think one statement by Roache that should have gotten more critical scrutiny is this (in response to a question on whether Hitler deserved eternal punishment):

Roache: It’s tough to say. If you start out with the premise that a punishment should be proportional to the crime, it’s difficult to think of a crime that could justify eternal imprisonment. You could imagine giving Hitler one term of life imprisonment for every person killed in the Second World War. That would make for quite a long sentence, but it would still be finite. The endangerment of mankind as a whole might qualify as a sufficiently serious crime to warrant it. As you know, a great deal of the research we do here at the Oxford Martin School concerns existential risk. Suppose there was some physics experiment that stood a decent chance of generating a black hole that could destroy the planet and all future generations. If someone deliberately set up an experiment like that, I could see that being the kind of supercrime that would justify an eternal sentence.

Me: I think human reason and wisdom are insufficient to justify any confidence — whatsoever — that we should, if we could, hand out a sentence of eternal suffering on anybody. Moreover, her hypothetical case — "a physics experiment that stood a decent chance of generating a black hole that could destroy the planet and all future generations" — is a further blow to the idea that such a punishment might be justified. Consider that there already have been dubious claims about physics experiments having the potential to destroy the universe. What exactly would constitute the "decent chance" required for some particle experiment to be labeled a "supercrime" and, given that even physicists often disagree about wildly speculative possibilities, whom would we entrust to sign off on the eternal damnation sentence?