Where injurious circumstances are under the management of a defendant and are such as would not occur in the ordinary course of things, the law allows a plaintiff to invoke the maxim res ipsa loquitur and establish a prima facie case of negligence.
This will enable them to succeed unless the defendant can rebut it with a plausible account. Thus, if a barrel falls out of an upstairs window, an injured person can say that the thing speaks for itself.
So can someone who is knocked down while walking along the edge of a dual carriageway the postulated ordinary course of things being that he "was behaving as an ordinary, prudent pedestrian" and if the defendant driver cannot proffer any non-culpable explanation he will be held liable according to Widdowson v Newgate Meat Corporation.
The Court of Appeal's judgment illustrates, however, the need for care when considering contributory negligence in a case which, with no factual evidence from either side, has been decided by res ipsa loquitur.
In Widdowson, Lord Justice Brooke held that the plaintiff was equally blameworthy and Lord Justice Nourse saw no alternative other than apportioning the blame equally between the defendant driver and the plaintiff.
The Law Reform (Contributory Negligence) Act 1945 requires the court to have regard to "the claimant's share in the responsibility for the damage", and this will often but not always involve examining how# far the plaintiff was accountable for what happened, rather than just his# #responsibility for the extent of the injury he suffered.
But for the Lord Justices simply to "assess... contributory negligence at 50 per cent" in language clearly indicating that each felt the plaintiff was as much to blame for the incident as the defendant, on the one hand conflates the separate issues of liability and contributory negligence and on the other invites the argument that there is no room for res ipsa loquitur.
If the parties are equally to blame for the incident itself, then it was not in the ordinary course of things (because the plaintiff cannot have been behaving as an ordinary prudent pedestrian). So in the absence of evidence he fails to establish liability.