1. In half the states (including Illinois), it’s legal to use deadly force against a robber — including against unarmed robbers, where you think you’re in no danger of death or serious bodily injury. In Illinois, for instance, you can use deadly force against any “forcible felony,” which includes any robbery, which in turn covers “knowingly tak[ing] property … from the person or presence of another by the use of force or by threatening the imminent use of force.” In nearly all states, using deadly force merely to prevent theft or to recapture stolen property is generally not allowed (though using nondeadly force is). But in the states I describe here, using deadly force to prevent forcible theft from one’s person (or, in Illinois, even from one’s presence) is allowed.
2. But in all states, it’s legal to use deadly force when you reasonably believe that you are in danger of death or serious bodily injury (including rape). When someone is robbing you with a gun, and you sincerely believe that he might well use the gun, that belief is, to my knowledge, uniformly viewed by the law as reasonable. So you are generally free to shoot robbers who have deadly weapons, at least so long as they’re still engaged in the robbery, rather than running away.
3. The analysis is generally the same for using deadly force to defend someone else as for using it to defend yourself. The defenses have different labels, “defense of others” and “self-defense,” but they are analyzed in much the same way.
4. The law might in principle require that the force not be unnecessarily severe — for instance, if a small child is punching you, and you can stop this by pushing him away but you instead deliver a knockout punch to his head, perhaps that might be seen as excessive. And, as noted above, using deadly force against mild attacks is generally seen as excessive, too. But once the use of deadly force is authorized, the law doesn’t insist on shooting “to wound” before shooting to kill. First, shooting to wound is risky for the shooter, since it’s more likely that you’ll miss, or that you’ll hit but won’t stop the attacker, who would then be able to kill or wound you. Second, shooting to wound is generally riskier for bystanders, since it’s more likely that you’ll miss the target and might hit someone else. Third, and relatedly, when you are in combat for the first time (and likely even when it’s not the first time), you can’t reasonably be expected to achieve Jack Bauer levels of calmness and precision.
5. The law also looks at the facts as the defender reasonably believed them to be. If the defender reasonably thinks the attacker had a real gun, he can act on that reasonable belief, even if it later turns out the gun was fake. And the defender’s evaluation of the situation generally won’t be scrutinized too closely with 20/20 hindsight (e.g., “if only he’d looked closely enough, he’d have recognized the gun wasn’t real”). The law recognizes that “Detached reflection cannot be demanded in the presence of an uplifted knife” (to borrow a phrase from a closely related self-defense question).
6. In a few cases, of course, such defensive use of force can also injure or even kill innocent bystanders, just as police use of force sometimes injures or kills innocent bystanders. But such harms to bystanders aren’t considered criminal, unless the defender’s action is seen as grossly negligent, in light of the circumstances that the defender was facing. Perhaps shooting an apparently unarmed purse-snatcher, even if considered lawful self-defense against robbery, might be considered grossly negligent if it injures a bystander. But if the defender’s life was in jeopardy, even dangerous attempts to preserve it will be seen as reasonable (or at least not grossly negligent). To quote the Pennsylvania Supreme Court in Commonwealth v. Fowlin (1998),
[T]he law … does not require one to stand by helplessly while he is injured or killed by an assailant….[W]hen one is the victim of an attack, the assailant, not the victim, picks the time, the place, the manner, and the circumstances of the attack. Leisurely assessment of the circumstances and the danger to others is almost never a feature of such an assault, and most often, the best the victim can do is to mount a defense which hopefully will preserve his life. In many cases, the victim has only seconds to act in order to avoid injury or death. In this case, Fowlin was accosted by three men who assaulted him with pepper spray and simultaneously drew a handgun. Fowlin assumed, with reason, that they intended to kill or seriously injure him. He acted instinctively and within our law in defending himself.Any victim of crime who justifiably exercises his right of self-preservation may inadvertently injure a bystander. Admittedly, this court could fashion a rule of law which holds the defender criminally liable, but in doing so, we would have furthered no policy of the criminal law. Instead, we would have punished a person who was acting within his instinct for self-preservation and, in an appropriate case, within the boundaries of our law.
7. One can certainly debate the right lines to be drawn here. For instance, as I noted above half the states don’t allow the use of deadly force against someone who is engaged in unarmed threat from the defender’s person. Likewise, the law generally doesn’t allow the use of deadly force against other theft, or against a punch or a slap.
But when it comes to people who are using what appear to be deadly weapons to commit crimes, the law broadly authorizes defenders to use deadly force against the criminals. And that doesn’t just let innocent victims protect their lives — it also protects victims against the injury of forcible compulsion. When someone tries to illegally force you to give him money, or to do or not do anything else, by threatening murder if you don’t obey, that is a form of slavery, temporary as it may be. Free men and women are not required to meekly go along, but retain the right to use whatever means they have to stop it.
So, from the law’s perspective, somebody did answer for what happened to Gildersleeve — that someone was Gildersleeve himself.