Doing nothing is legally safer than doing something, but you're not without hope if you pull the lever. Although you'll likely have committed murder or at least manslaughter, case law is littered with lenience in exigent circumstances, even where convictions have been affirmed.
Because this is a philosophical problem, there are plenty of opinions from that perspective, but not so many from a legal standpoint.
Let's assume that you're an innocent bystander, (not an employee of the railway company or the train company, etc) and have no duty to act.
If you do nothing, then it is unlikely that you would be charged with a crime - you had no duty to fulfill, and therefore not negligent. There's little doubt that not pulling the lever is the safer option.
More interesting is when you choose to pull the lever - then it's probable that you would have charges of murder, or at least manslaughter, brought against you by the state. What defenses does the law offer?
Let's assume that you are aware that pulling the lever will kill a person.
The primary defence is a legal principle of necessity: where your criminal actions are not protected or excluded by some other statute or principle, the fact that you were obliged to take this action in order to prevent some greater harm may safeguard you from penalties.
There are certain elements of necessity:
- That you did not create the danger that caused you to commit the crime;
- That you ceased the criminal activity as soon as practicably possible;
- That you had no reasonable alternative; and
- The harm that you prevented was greater than the harm that you caused.
I see such a defense only possibly falling over on (4), where the prevented and caused harm, in the case of human lives, are inherently very subjective.
Unfortunately, each state has different rulings regarding the threshold for evidence of this defense.
One of the most famous cases where necessity was attempted as a defense to murder, with remarkable parallels to this hypothetical, is that of R v Dudley and Stephens:
- A crew of four found themselves on a lifeboat at sea with no food and no water, and with no prospect of rescue.
- One of them was a child (Parker) and was nearing death and unconscious.
- Two of them (Dudley and Stephens), after some discussion over drawing lots, decided that the child would be killed before his natural death, in order that his blood be better preserved for drinking.
The last crew member, Brooks, was silent on the matter.
- After killing Parker, Dudley, Stephens and Brooks fed on Parker's body.
- During the trial, the matter of necessity as a defense to murder was considered.
- The judges found that there was no common law defence of necessity to murder, and Dudley and Stephens were sentenced to death with a recommendation for mercy.
- The Home Secretary commuted their sentences to six months' imprisonment.
This case concerns essentially the choice you're making in the trolley problem: either the four crew members were going to die, or one of them would definitely die and the others might live. It's easy to say that they should have just waited, but they didn't have the benefit of hindsight.
It's also a great example of a situation where although the law says one thing, it doesn't align with our morals and ethics, and while it's a UK case, I would wager that almost every lawyer in common law countries would have heard about it.