The K-Zone: causation in criminal liability

In English law, the term `causation' has a meaning that is similar to the one employed in everyday speech. To say that X caused grevious bodily harm to Y by, say, hitting him over the head with a stick, uses the common meaning of `cause'. However, in law causation has a few extra features.

The action of the accused need not be the only contribution to the actus reus, nor even the major contribution, but it must be a `substantial and operating cause'.
Causation need not be direct, but there must be an unbroken `chain of causation' between the accused's act and the consequences.
Causation may not have to be physical; it may be `moral'. For example, in RVMcKechnie1991 the accussed caused injuries that prevented an urgent operation being performed on the victim. The injuries themselves would not have been fatal, but the inability to operate was eventually fatal.

A common test for causation is the `but for' test. If it is true that `but for' the act of the accused the victim would not have suffered the same consequences, then there is causation. It is often thought that the `but for' rule can lead to absurd regress (`` `but for' the accused's parents having met, the accused would not have been born...''), and that the rule is defeated by a `break in the chain of causation'. Law reports are replete with discussions about whether some act is a NovusActusInterveniens, that is, some new act that intervenes in the sequence of causation. However, in many cases this discussion misses the point. In the absurd case of whether the acts of X's parents in giving birth to X are a cause of some act done by X, the issue of causation is irrelevant as X's parents did not have mens rea for the act by X (we assume). Whether there is causation but not mens rea, or there is no causation at all, is irrelevant, as there is no liability either way. Similarly, if X makes a bomb to kill Y, and Z delivers it believing it to be a cake, then clearly X is liable and not Z. It makes no difference whether Z is held not to break the chain of causation, as there is no question that he is liable, or that X is not.

Whether the doctrine of chain of causation is valid or not, in general, the following are held to break the chain of causation:

wildly unpredictable responses of the victim, that contribute to the injury;
assumption of liability by a third party;
`acts of God'.

On the other hand, the following are usually taken not to break the chain of causation:

innocent acts of other parties (e.g., delivering a bomb believing it to be a cake);
withdrawal of medical treatment when it is clear that the patient is beyond hope;
ommissions of the victim to seek treatment for injuries;
unusual sensitivity of the victim to a particular kind of injury

CriminalLaw