Ok so you're not talking about CSA in general;, in fact you're not talking about any crime in particular, but rather the power possessed by those who perpetrate them?

How would this work? Is torture ok? How do you determine who is powerful enough? How do you prevent uncertainty and/or other powerful interests hijacking the justice system?

You know what's easier and remains in line with fundamental values of liberal justice systems? Just no death penalty. Start by actually enforcing laws against the powerful, with penniless and impotent lifetimes spent in prison. Avoid creating martyrs and endless cycles of violence and retribution.

And in the case of CSA, again, avoid creating piles of dead kids. If all of these criminals thought they were facing the death penalty the crimes and corruption would just get worse, to absolutely no benefit to us other than satisfying emotional blood lust.