Proximate cause
In the law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, a proximate cause is an event sufficiently related to a legally recognizable injury to be held the cause of that injury. There are two types of causation in the law, cause-in-fact and proximate (or legal) cause. Cause-in-fact is determined by the "but-for" test: but for the action, the result would not have happened. For example, but for running the red light
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...

, the collision would not have occurred. For an act to cause a harm, both tests must be met; proximate cause is a legal limitation on cause-in-fact.

But for test

A few circumstances exist where the but for test is complicated, or the test is ineffective. The primary examples are:
  • Concurrent causes. Where two separate acts of negligence combine to cause an injury to a third party, each actor is liable. For example, a construction worker
    Construction worker
    A construction worker or builder is a professional, tradesman, or labourer who directly participates in the physical construction of infrastructure.-Construction trades:...

     negligently leaves the cover off a manhole
    A manhole is an opening used to gain access to sewers or other underground structures, usually for maintenance.Manhole may also refer to:* Manhole , a metal band from Los Angeles* The Manhole, a computer game...

    , and a careless driver
    Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

     negligently clips a pedestrian
    A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

    , forcing the pedestrian to fall into the open manhole. Both the construction worker and the careless driver are equally liable for the injury to the pedestrian. This example obeys the but for test. The injury could have been avoided by the elimination of either act of negligence, thus each is a but for cause of the injury.
  • Sufficient combined causes. Where an injury results from two separate acts of negligence, either of which would have been sufficient to cause the injury, both actors are liable. For example, two campers in different parts of the woods negligently leave their campfire
    A campfire is a fire lit at a campsite, to serve the following functions: light, warmth, a beacon, a bug and/or apex predator deterrent, to cook, and for a psychological sense of security. In established campgrounds they are usually in a fire ring for safety. Campfires are a popular feature of...

    s unattended. A forest fire
    A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

     results, but the same amount of property damage would have resulted from either fire. Both campers are equally liable for all damage. A famous case establishing this principle in the United States is Corey v. Havener.
  • In the United States, the rule of Summers v. Tice holds that where two parties have acted unreasonably, but only one causes an injury to a third party, the burden shifts to the negligent parties to prove that they were not the cause of the injury. In that case, two hunters negligently fired their shotgun
    A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...

    s in the direction of their guide, and a pellet
    Lead shot
    Lead shot is a collective term for small balls of lead. These were the original projectiles for muskets and early rifles, but today lead shot is fired primarily from shotguns. It is also used for a variety of other purposes...

     lodged in his eye. Because it was impossible to tell which hunter fired the shot that caused the injury, the court held both hunters liable.
  • Market share evidence. Injury or illness is occasioned by a fungible product made by all the manufacturers joined together in a lawsuit. The injury or illness is due to a design hazard, with each having been found to have sold the same type of product in a manner that made it unreasonably dangerous, there is inability to identify the specific manufacturer of the product or products that brought about the Plaintiff’s injury or illness and there are enough of manufacturers of the fungible product joined in the lawsuit, to represent a substantial share of the market. Any damages would then be divided according to the market share ratio.

Problems with "but for" causation

Since but-for causation is very easy to show and does not assign culpability
Culpability descends from the Latin concept of fault . The concept of culpability is intimately tied up with notions of agency, freedom and free will...

 (but for the rain, you would not have crashed your car the rain is not morally or legally culpable but still constitutes a cause), there is a second test used to determine if an action is close enough to a harm in a "chain of events" to be a legally culpable cause of the harm. This test is called proximate cause.

There are several competing theories of proximate cause.


The most common test of proximate cause under the American legal system is foreseeability. It determines if the harm resulting from an action was reasonably able to be predicted. The test is used in most cases only in respect to the type of harm. It is foreseeable that throwing a baseball at someone could cause them a blunt-force injury
Blunt trauma
In medical terminology, blunt trauma, blunt injury, non-penetrating trauma or blunt force trauma refers to a type of physical trauma caused to a body part, either by impact, injury or physical attack; the latter usually being referred to as blunt force trauma...

. But proximate cause is still met if a thrown baseball misses the target and knocks a heavy object off a shelf behind them, which causes a blunt-force injury.

This is also known as the "extraordinary in hindsight" rule.

Direct Causation

Direct causation is a minority test, which addresses only the metaphysical concept of causation. The main thrust of direct causation is that there are no intervening causes between an act and the resulting harm. An intervening cause has several requirements: it must 1) be independent of the original act, 2) be a voluntary human act or an abnormal natural event, and 3) occur in time between the original act and the harm.

Direct causation is the only theory that addresses only causation, and does not take into account the culpability of the original actor.

Risk enhancement/causal link

The plaintiff must demonstrate that the defendant's action increased the risk that the particular harm suffered by the plaintiff would occur. If the action were repeated, the likelihood of the harm would correspondingly increase. This is also called foreseeable risk.

Harm Within the Risk

The Harm Within the Risk (HWR) test determines whether the victim was among the class of persons who could foreseeably be harmed, and whether the harm was foreseeable within the class of risks. It is the strictest test of causation, made famous by Benjamin Cardozo in Palsgraf v. Long Island Railroad Co.
Palsgraf v. Long Island Railroad Co.
Palsgraf v. Long Island Railroad Co., 248 N.Y. 339, 162 N.E. 99 , was a decision by the New York Court of Appeals written by Chief Judge Benjamin Cardozo, a leading figure in the development of American common law and later a Supreme Court justice...

 case under New York state
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...


The first element of the test is met if the injured person was a member of a class of people who could be expected to be put at risk of injury by the action. For example, a pedestrian, as an expected user of sidewalks, is among the class of people put at risk by driving on a sidewalk, whereas a driver who is distracted by another driver driving on the sidewalk, and consequently crashes into a utility pole, is not.

The second prong of the test is whether the type of harm was in the class of expected harms. Giving a loaded gun to a young child gives rise to the expectation that someone could be shot by the child's firing the gun. If the child drops the gun and it breaks someone's foot, the HWR test fails, as a broken foot was not the type of harm anticipated.

The HWR test is no longer much used, outside of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 law. When it is used, it is used to consider the class of people injured, not the type of harm. The main criticism of this test is that it is preeminently concerned with culpability, rather than actual causation.

The "Risk Rule"

Referred to by the Reporters of the Second and Third Restatements of the Law of Torts as the "scope-of-the-risk" test, the term "Risk Rule" was coined by Harvard Law Professor Robert Keeton. The rule is that “[a]n actor’s liability is limited to those physical harms that result from the risks that made the actor’s conduct tortious.” Thus, the operative question is "what were the particular risks that made an actor's conduct negligent?" If the injury suffered is not among those risks, there can be no recovery. Two examples will illustrate this principle:
  • The classic example is that of a father who gives his child a loaded gun, which she carelessly drops upon the plaintiff’s foot, causing injury. The plaintiff argues that it is negligent to give a child a loaded gun and that such negligence caused the injury, but this argument fails, for the injury did not result from the risk that made the conduct negligent. The risk that made the conduct negligent was the risk of the child accidentally firing the shotgun; the harm suffered could just as easily have resulted from handing the child an unloaded gun.

  • Another example familiar to law students is that of the restaurant owner who stores rat poisoning above the grill in his luncheonette. The story is that during the lunch rush, the can explodes, severely injuring the chef who is preparing food in the kitchen. The chef sues the owner for negligence. The chef may not recover. Storing rat poisoning above the grill was negligent because it involved the risk that the chef might inadvertently mistake it for a spice and use it as an ingredient in a recipe. The explosion of the container and subsequent injury to the chef was not what made the chosen storage space risky.

The most obvious objection to this approach is that it requires courts to consider an arguably endless possibility of hypothetical situations. Not only can such an undertaking be an exercise in futility, but this approach lacks even a minimal amount of precision such that parties might be able to predict outcomes and results during litigation. Notwithstanding the already-complex nature of this and other questions relating to proximate or legal cause, this fluid standard could be misused by plaintiff-friendly or defense-favoring judges in attempts to vindicate their own personal philosophies regarding the appropriate reach of tort law.


The doctrine of proximate cause is notoriously confusing. The doctrine is phrased in the language of causation, but in most of the cases in which causation is contested, there is not much real dispute that the defendant but-for caused the plaintiff's injury. The doctrine is actually used by judges to limit the scope of the defendant's liability to a subset of the total class of potential plaintiffs who suffered some harm from the defendant's actions. For an understanding of the broader view of causation which proximate cause circumscribes, see Butterfly effect
Butterfly effect
In chaos theory, the butterfly effect is the sensitive dependence on initial conditions; where a small change at one place in a nonlinear system can result in large differences to a later state...


For example, in the two famous Kinsman Transit cases from the 2nd Circuit
United States Court of Appeals for the Second Circuit
The United States Court of Appeals for the Second Circuit is one of the thirteen United States Courts of Appeals...

 (exercising admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...

 jurisdiction over a New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 incident), it was clear that mooring a boat improperly could lead to the risk of a boat drifting away and crashing into another boat, and that both boats could crash into a bridge, which collapsed and blocked the river, and in turn, the wreckage could flood the land adjacent to the river, as well as prevent any traffic from traversing the river until it had been cleared. But under proximate cause, the property owners adjacent to the river could sue
Sue or SUE may refer to:* Door County Cherryland Airport in Sturgeon Bay, Wisconsin, USA* The action of filing a lawsuit.* Subsurface Utility Engineering* .sue, alternative name for ARC -Places:...

 (Kinsman I), but not the owners of the boats or the cargoes which could not move until the river was reopened (Kinsman II).

Therefore, in 2001, the American Law Institute
American Law Institute
The American Law Institute was established in 1923 to promote the clarification and simplification of American common law and its adaptation to changing social needs. The ALI drafts, approves, and publishes Restatements of the Law, Principles of the Law, model codes, and other proposals for law...

 proposed in a draft of the Restatement (Third), Torts: Liability for Physical Harm (Basic Principles) that proximate cause should be replaced with scope of liability.

Historiographical usage

The term "proximate cause" is also used by historians, in the sense of a specific event or incident setting off an event, such as a war or revolution, which had deeper roots and causes. An often cited example is the assassination of Archduke Franz Ferdinand of Austria
Archduke Franz Ferdinand of Austria
Franz Ferdinand was an Archduke of Austria-Este, Austro-Hungarian and Royal Prince of Hungary and of Bohemia, and from 1889 until his death, heir presumptive to the Austro-Hungarian throne. His assassination in Sarajevo precipitated Austria-Hungary's declaration of war against Serbia...

 at Sarajevo
Sarajevo |Bosnia]], surrounded by the Dinaric Alps and situated along the Miljacka River in the heart of Southeastern Europe and the Balkans....

, the event which directly set off World War I. It is generally assumed by historians that the war was actually caused by the sharpening rivalries between the European powers and the setting up of rival military alliances and so even had the assassination not occurred, some other incident would have still have set off the war. The distinction between an immediate proximate cause and the more fundamental causes has become a staple of historical research. This example does not pass the "but for" test as other similar triggers could have tipped the scale.

Further reading

  • Michael S. Moore, The Metaphysics of Causal Intervention, 88 L. 827 (2000).
  • Leon A. Green
    Leon A. Green
    Leon Green was a noted U.S. legal realist and long-tenured dean of Northwestern University School of Law . He also served as professor at Yale Law School and the University of Texas School of Law .Born in Oakland, Louisiana, Green earned an A.B...

    , The Rationale of Proximate Cause (1927).
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