chapter  6
Probability
Pages 10

The probability test of intervening causation postulates that the more likely the intervention the less likely it is to break the chain of causation. The leading contemporary proponent of this test is Lord Reid who stated in Home Office v Dorset Yacht Co. Ltd1 that the true novus actus test was not whether the intervention was ‘a mere foreseeable possibility’ but rather was it ‘very likely’. Judicial expressions such as ‘abnormal’ or ‘coincidental’ on the one hand and ‘in the ordinary course of things’ and ‘natural and probable consequence’ on the other may be plotted on a continuum which calibrates the probability or likelihood (or lack thereof) of the intervening event happening as a result of the defendant’s negligence. The probability test has been most widely accepted and applied in England and the United States of America but it has already enjoyed its heyday and is now in a state of decline, perhaps because of its potential to allow reasonably foreseeable acts to break the causation in an era of ever-increasing imposition of civil liability on defendants and their insurers.