I did not get the sense @newsbinator was trying to remove the question to an entirely hypothetical realm, but stipulating that we somehow have this knowledge wi

I did not get the sense @newsbinator was trying to remove the question to an entirely hypothetical realm, but stipulating that we somehow have this knowledge with hypothetical 100% certainty is fair enough. (1) is unknowable. (2) and (3) describe many, many people that are not generally considered to be serial killers (e.g., a soldier). If a 'known serial killer' were experimented on and died, (2) and (3) could also describe the researchers doing the experimentation. We could modify (1) to say, "...and we have 100% certainty of this." But I guess really not certain what value the question has if we basically require 100% certain knowledge of the events and the internal state of the perpetrator. A 'no' answer would mean 'no' in the real world, too, but a 'yes' answer doesn't really tell us anything about the real world.