In criminal law, an act or omission that produces a consequence is called causation. To prove that the consequence was caused by the defendant’s act, the prosecution must show that; the defendant’s conduct was the factual cause of the consequence, it was the legal cause of the consequence and there was no intervening act from the victim or a third party that broke the chain of causation.
To test whether the defendant’s conduct was the factual cause of the consequence, the ‘but for’ test is used. This tests whether the consequence would have happened but for the defendant’s act or omission. An example case where the ‘but for’ test was used is Pagett (1983), where the defendant took his girlfriend hostage, then when police called on him to surrender, he came outside using the girl as a human shield and opened fire. When the police returned fire, they killed the girlfriend. Because the police wouldn’t have shot the girl ‘but for’ the defendant’s conduct, the defendant was liable for manslaughter. An example where the ‘but for’ test was not satisfied was White (1910), where a man poisoned his mother’s drink in an attempt to kill her. She died before she drank the tea, and therefore he was not the factual cause of death and not guilty of murder, however, he was guilty of attempted murder.
The second half of causation is whether the defendant’s actions were the legal cause of the consequence. The essential rule is that the defendant’s act must be more than a ‘minimal’ contribution to the consequence, the act doesn’t have to be a substantial cause. This was reinforced in cases such as Kimsey (1996), where the de minimis principle was used, stating that the defendant’s act must have ‘more than a slight or trifling link’ to the consequence. In Kimsey, the defendant was involved in a high speed car chase with a friend, and the friend crashed and died. There was no clear or solid evidence suggesting that the defendant’s actions were the cause of the accident, however, as the defendant’s actions were ‘more than a slight and trifling link’, the defendant was convicted of death by dangerous driving, which was upheld by the Court of Appeal. This case also demonstrates how, even though there may be more than one contributing factor to the consequence, each cause can still be liable, as in this case, the defendant was only half the cause, as the other driver was taking part in the chase as well.