This article grapples with the question of cause in fact in lawsuits against handgun manufacturers based on theories of negligent marketing. We note that the conventional test for cause in fact -- whether the defendant's breach of duty was more likely than not the cause of the plaintiffs injury -- is something which is very hard for plaintiffs in these cases to prove given the fact that at least half of handguns used in crime are not negligently marketed. Thus, even if a jury finds that the defendant breached a duty, they still must deal with the problem of the indeterminate plaintiff.

We consider whether a looser test for cause in fact, such as the one articulated by Wex Malone in 1956, could help make sense of the handgun cases. Malone argued that in certain classes of cases-such as those involving shipowners who failed to provide lifesaving equipment--a court would be justified in sending a case to the jury even if the court believed that it was not likely that the plaintiff's injury would have been prevented by the missing equipment. We examine Malone's various policy arguments for allowing plaintiffs to sue for the loss of a "gamblers chance" and conclude that it would be a violation of basic tort law and fairness to extend Malone's approach to the handgun cases without modification.

The modification we propose is that plaintiffs in the handgun cases can recover for negligent marketing only that portion of their injury which corresponds to the increase in risk which the defendants' breach of duty added to the existing risk. We therefore adopt and apply the proportional causation arguments developed by David Rosenberg and those courts who have considered 'loss of a chance' in the context of medical malpractice. We then go through various recent cases involving allegations of negligent marketing and apply our theory to these cases, detailing what a court should require a plaintiff to prove. We conclude by arguing that courts in the handgun cases need not abandon their fundamental commitment to cause in fact as an element of negligence, since our approach allows victims of handgun violence to address manufacturers' alleged breaches of duty without making them liable for a vast number of injuries which they did not cause.