In tort law, there is a relationship among proximate cause, concurrent cause, and superseding cause.  Proximate cause results from a sequence of events unbroken by a superseding cause, so that its causal viability continued until the moment of injury or at least until the advent of the immediate injurious force.[1]  The test of proximate cause is whether the defendant’s conduct is a substantial factor in bringing about the plaintiff’s injuries.[2]

            A concurrent cause is one that is contemporaneous and coexistent with the defendant’s wrongful conduct and actively cooperates with the defendant’s conduct to bring about the injury.[3]  Finally, a superseding cause is an act of a third person or other force which by its intervention prevents the actor from being liable for harm to another which his antecedent negligence is a substantial factor in bringing about.[4]

            The function of the doctrine of superseding cause is not to serve as an independent basis of liability, regardless of the conduct of a third party whose negligent conduct may have contributed to the plaintiff’s loss.[5]  The function of the doctrine is to define the circumstances under which responsibility may be shifted entirely from the shoulders on one person, who is determined to be negligent, to the shoulders of another person, who may also be determined to be negligent, or to some other force.[6]  Thus, the doctrine of superseding cause serves as a device by which one admittedly negligent party can, by identifying another’s superseding conduct, exonerate himself from liability by shifting the causation element entirely elsewhere.  If a third person ‘s negligence is found to be the superseding cause of the plaintiff’s injuries, that negligence, rather than the negligence of the party attempting to invoke the doctrine of superseding cause, is said to be the sole proximate cause of the injury.[7]

            The circumstances under which a defendant’s liability for negligence shifts entirely to the superseding conduct of a third person has been well defined in Connecticut’s case law.  Even if a plaintiff’s injuries are in fact caused by a defendant’s negligence, a superseding cause may break that causal connection it is so entirely supersedes the operation of the defendant’s negligence that it alone, without his negligence contributing thereto in any degree, produces the injury; or it must be the nonconcurring culpable act of a human being who is legally responsible for such act.  If a defendant’s negligence was a substantial factor in producing the plaintiff’s injuries, the defendant would not be relieved from liability for those injuries even though another force concurred to produce them.[8]

            The terms “intervening cause” and “superseding cause” have been used interchangeably.  The Restatement of Torts makes clear that the doctrine is properly referred to as “superseding cause and that it embodies within it the concept of an “intervening force.”[9]  A superseding cause is an act of a third person or other force which by its intervention prevents the actor from being liable for harm to another which his antecedent negligence is a substantial factor in bringing about.[10] 

            Regarding intervening cause the standard set forth in § 442B of the Restatement (Second) of Torts is that where the negligent conduct of the actor creates or increases the risk of a particular harm and is a substantial factor in causing that harm, the fact that the harm is brought about through the intervention of another force does not relieve the actor of liability, except where the harm is intentionally caused by a third person and is not within the scope of the risk created by the actor’s conduct.[11]  To be within the scope of the risk, the harm actually suffered must be of the same general type as that which makes the defendant’s conduct negligent I n the first instance.  Moreover, if the defendant’s conduct is a substantial factor in bringing about harm to another, the fact that the defendant neither foresaw nor should have foreseen the extent of the harm or the manner in which it occurred does not prevent him from being liable.[12]

            In Barry v. Quality Steel Products., 263 Conn. 424 (2003), the Connecticut Supreme Court abandoned the doctrine of superseding cause in favor of a proximate cause analysis in most circumstances because the doctrine no longer served a useful purpose in Connecticut’s tort system of comparative negligence[13] and apportionment,[14] pursuant to which defendants are responsible solely for their proportionate share of the injury suffered by the plaintiff.[15]  Following Barry, therefore, the issue of whether the subsequent negligence of a third party breaks the causal connection between the tortfeasor’s negligence and the harm suffered by the injured party is determined on the basis of traditional proximate cause analysis.[16]

            However, Barry[17] retained the doctrine in cases of intervening criminal misbehavior.