Moriarty wants to kill Holmes but doesn’t want to run the risk of being convicted for murder. So he plans to get an innocent person to do the dirty work for him. Here’s what he does.
First, he persuades Holmes (with whom he is ostensibly on good terms) and three of his Baker Street Irregulars to take part in a real-life philosophical experiment. He will tie the three Irregulars to a trolley track, near to a spur on which Holmes will be tied. He will wait till there are a number of bystanders near where the spur branches off, then release a trolley down the main track in the direction of the Irregulars, and wait to see if one of the bystanders throws the lever to divert the trolley onto the spur. The experiment will provide the philosophical world with important data on the famous trolley problem.
Moriarty shows everyone that the trolley has an automatic braking mechanism that will prevent it hitting the Irregulars if the lever is not thrown. This mechanism really does work, but Moriarty has adjusted it so that if the trolley is sharply diverted onto another track, it will fail. Everyone agrees to take part.
It all goes to plan. Moriarty releases the trolley, a bystander, Doyle, sees the trolley and the people on the tracks, does some rapid moral reasoning, and operates the lever, believing that this will result in the death of the person on the spur. The trolley goes onto the spur, its braking mechanism fails, and Holmes is killed.
Moriarty’s plan has worked. Holmes is dead, yet Moriarty did not kill him. If Doyle had not intervened, no one would have been harmed. Instead, Doyle freely chose to do something which he believed would kill Holmes.
Or was there a flaw in the plan? Did Moriarty commit a crime? If so, what was it? Who is morally responsible for Holmes’s death? Does it matter if you think Doyle’s moral reasoning was faulty?
(Revised and expanded after twitter discussion with @JulianSales2, @FillinghamLydia, and @tylerhower.)