What breaks the chain of causation

Plaintiff, employed by the Defendant as a maintenance linesman was injured during the course of his work when he fell down a railway embankment. The Plaintiff could not see where he was going because the torch he had been given by the defendant was not working. After the accident, plaintiff was unable to work and received workers compensation. He began to worry about how he could support his family once his entitlements ran out. Plaintiff began to grow Indian hemp which he intended to produce and sell marijuana Plaintiff was arrested, convicted and imprisoned.

Decision:

Under the but for test, “but for” the defendant’s negligence, the plaintiff would not have committed the criminal act.
On appeal, the majority of the court of appeal held that as a matter of policy (i.e. common sense), the court should not hold that imprisonment was caused by the defendant’s (appellant Railway authority’s) negligence.
“The application of the simple but for test to determine causation would be inappropriate… it would be quite unreal to find that the defendant caused the plaintiff to engage in criminal conduct”.
The Railway Authority was not negligent.

The section 11(1)(a) combines the ‘but for’ test and the balance of probabilities tests which developed at common law.

What can break the chain of Causation – Novus Actus Interveniens (An intervening act)

Intervening Act and Causation

A plea of novus actus interveniens, meaning “a new intervening act” allows the defendant to escape liability if his or her negligence was not the proximate cause of the plaintiff’s loss, damage or injury. That is because the loss, damage or injury was caused by something which happened after the defendant’s negligent act or omission.
The chain of causation between the defendant’s negligence and the plaintiff’s injury, loss or damage is broken: Yates v Jones (1990).
Facts:

Plaintiff injured in a car accident was offered heroin as a form of pain relief by one of her hospital visitors. She became addicted to heroin and the need for $900 per day for heroin eventually devoured all her money and her mother’s money. P sued the driver of the motor vehicle for $25,000 in general damages and $45,000 damages representing the heroin addiction.