When is attempted murder more acceptable than harming someone by accident?

Dan, a scientist working on dangerous viruses, is giving a visitor a tour of his lab. Before this happens, all test tubes containing disease-causing agents must be sealed in a chamber with a flick of a switch. Unfortunately, the switch broke recently and it hasn’t been repaired yet. Entering the room means certain death. Dan knows this but still, he bids the visitor to enter. The inevitable happens; they become sick and they die. Would you consider Dan’s actions to be immoral? What if, in a parallel universe, the visitor miraculously survived? Does that change your views of Dan’s deeds? What if Dan didn’t know about the broken switch? For most of us, the answers are clear. If Dan knew about the broken switch, he was wrong to send in the visitor to potential death, regardless of whether they actually perished. But bizarrely, not everyone would see it that way. ...