Causation (law)
Causation is the "causal relationship between the defendant's conduct and end result". In other words, causation provides a means of connecting conduct with a resulting effect, typically an injury. In criminal law, it is defined as the actus reus from which the specific injury or other effect arose and is combined with mens rea to comprise the elements of guilt. Causation applies only where a result has been achieved and therefore is immaterial with regard to inchoate offenses.
Background concepts
Legal systems more or less try to uphold the notions of fairness and justice. If a state is going to penalize a person or require that person pay compensation to another for losses incurred, liability is imposed according to the idea that those who injure others should take responsibility for their actions. Although some parts of any legal system will have qualities of strict liability, in which the mens rea is immaterial to the result and subsequent liability of the actor, most look to establish liability by showing that the defendant was the cause of the particular injury or loss.Even the youngest children quickly learn that, with varying degrees of probability, consequences flow from physical acts and omissions. The more predictable the outcome, the greater the likelihood that the actor caused the injury or loss intentionally. There are many ways in which the law might capture this simple rule of practical experience: that there is a natural flow to events, that a reasonable man in the same situation would have foreseen this consequence as likely to occur, that the loss flowed naturally from the breach of contractual duties or tortuous actions, etc. However it is phrased, the essence of the degree of fault attributed will lie in the fact that reasonable people try to avoid injuring others, so if harm was foreseeable, there should be liability to the extent that the extent of the harm actually resulting was foreseeable.
Relationship between causation and liability
Causation of an event alone is insufficient to create legal liability.Sometimes causation is one part of a multi-stage test for legal liability. For example, for the defendant to be held liable for the tort of negligence, the defendant must have owed the plaintiff a duty of care, breached that duty, by so doing caused damage to the plaintiff, and that damage must not have been too remote. Causation is just one component of the tort.
On other occasions, causation is the only requirement for legal liability. For example, in the law of product liability, the courts have come to apply to principle of strict liability: the fact that the defendant's product caused the plaintiff harm is the only thing that matters. The defendant need not also have been negligent.
On still other occasions, causation is irrelevant to legal liability altogether. For example, under a contract of indemnity insurance, the insurer agrees to indemnify the victim for harm not caused by the insurer, but by other parties.
Because of the difficulty in establishing causation, it is one area of the law where the case law overlaps significantly with general doctrines of analytic philosophy to do with causation. The two subjects have long been intermingled.
Establishing causation
Where establishing causation is required to establish legal liability, it usually involves a two-stage inquiry, firstly establishing 'factual' causation, then legal causation. Factual causation must be established before inquiring into legal or proximate causation.Establishing factual causation
The usual method of establishing factual causation is the but-for test. The but for test inquires "But for the defendant's act, would the harm have occurred?" A shoots and wounds B. We ask "But for A's act, would B have been wounded?" The answer is "No." So we conclude that A caused the harm to B. The but for test is a test of necessity. It asks was it "necessary" for the defendant's act to have occurred for the harm to have occurred. In New South Wales, this requirement exists in s 5D of the Civil Liability Act 2002, reinforcing established common law principles.One weakness in the but-for test arises in situations where each of several acts alone are sufficient to cause the harm. For example, if both A and B fire what would alone be fatal shots at C at approximately the same time, and C dies, it becomes impossible to say that but-for A's shot, or but-for B's shot alone, C would have died. Taking the but-for test literally in such a case would seem to make neither A nor B responsible for C's death.
The courts have generally accepted the but for test notwithstanding these weaknesses, qualifying it by saying that causation is to be understood "as the man in the street" would, or by supplementing it with "common sense".
This dilemma was handled in the United States in State v. Tally,, where the court ruled that: "The assistance given... need not contribute to criminal result in the sense that but for it the result would not have ensued. It is quite sufficient if it facilitated a result that would have transpired without it." Using this logic, A and B are liable in that no matter who was responsible for the fatal shot, the other "facilitated" the criminal act even though his shot was not necessary to deliver the fatal blow.
However, legal scholars have attempted to make further inroads into what explains these difficult cases. Some scholars have proposed a test of sufficiency instead of a test of necessity. H. L. A. Hart and Tony Honoré, and later Richard Wright, have said that something is a cause if it is a "necessary element of a set of conditions jointly sufficient for the result". This is known as the NESS test. In the case of the two hunters, the set of conditions required to bring about the result of the victim's injury would include a gunshot to the eye, the victim being in the right place at the right time, gravity, etc. In such a set, either of the hunters' shots would be a member, and hence a cause. This arguably gives us a more theoretically satisfying reason to conclude that something was a cause of something else than by appealing to notions of intuition or common sense.
Hart and Honore, in their famous work Causation in the Law, also tackle the problem of "too many causes". For them, there are degrees of causal contribution. A member of the NESS set is a "causally relevant condition". This is elevated into a "cause" where it is a deliberate human intervention, or an abnormal act in the context. So, returning to our hunter example, hunter A's grandmother's birth is a causally relevant condition, but not a "cause". On the other hand, hunter A's gunshot, being a deliberate human intervention in the ordinary state of affairs, is elevated to the status of "cause". An intermediate position can be occupied by those who "occasion" harm, such as accomplices. Imagine an accomplice to a murder who drives the principal to the scene of the crime. Clearly the principal's act in committing the murder is a "cause". So is the accomplice's act in driving the principal to the scene of the crime. However, the causal contribution is not of the same level. Leon Green and Jane Stapleton are two scholars who take the opposite view. They consider that once something is a "but for" or NESS condition, that ends the factual inquiry altogether, and anything further is a question of policy.
Establishing legal causation
Notwithstanding the fact that causation may be established in the above situations, the law often intervenes and says that it will nevertheless not hold the defendant liable because in the circumstances the defendant is not to be understood, in a legal sense, as having caused the loss. In the United States, this is known as the doctrine of proximate cause. The most important doctrine is that of novus actus interveniens, which means a 'new intervening act' which may "cut the chain of causation".Proximate cause
The but-for test is factual causation and often gives us the right answer to causal problems, but sometimes not. Two difficulties are immediately obvious. The first is that under the but-for test, almost anything is a cause. But for a tortfeasor's grandmother's birth, the relevant tortious conduct would not have occurred. But for the victim of a crime missing the bus, he or she would not have been at the site of the crime and hence the crime would not have occurred. Yet in these two cases, the grandmother's birth or the victim's missing the bus are not intuitively causes of the resulting harm. This often does not matter in the case where cause is only one element of liability, as the remote actor will most likely not have committed the other elements of the test. The legally liable cause is the one closest to or most proximate to the injury. This is known as the Proximate Cause rule. However, this situation can arise in strict liability situations. Baker in the Glanville Williams and Dennis Baker Treatise of Criminal Law at paragraphs 10.9A to 10.9F argues that legal causation alone is sufficient establishing gross negligence manslaughter in duty to assist or prevent cases, since there is no way to know if the victim would have lived had the defendant done their duty and attempted to stop what was causing the victim's death by seeking help. Baker argues the case of R v Broughton EWCA Crim 1093 due to the issue of causal indeterminancy and the courts insistence that cause rest on it being provable that the victim would have lived had help being sought.Intervening cause
Imagine the following. A critically injures B. As B is wheeled to an ambulance, she is struck by lightning. She would not have been struck if she had not been injured in the first place. Clearly then, A caused B's whole injury on the "but for" or NESS test. However, at law, the intervention of a supervening event renders the defendant not liable for the injury caused by the lightning.The effect of the principle may be stated simply:
However, this does not apply if the Eggshell skull rule is used. Baker argues at paragraph 10.59 that the thin skull/ eggshell skull rule has no place in the criminal law and that even when appleid it will often have no effect since mens rea still needs to be established for the relevant offence and that most result crimes require mens rea. For details, see article on the Eggshell Skull doctrine.