In the leading case of Owens v Brimmell  QB 859, a passenger who was injured in a car accident had his damages reduced by 20% because he had accepted a ride with a driver whom must have known had too much to drink. In a much quoted dictum, Russell J held:
“A passenger may be guilty of contributory negligence if he rides with the driver of a car whom he knows has consumed alcohol in such quantity as is likely to impair to a dangerous degree that driver’s capacity to drive properly and safely”.
The passage can be misread as requiring actual or constructive knowledge.
In Malone v Rowan  3 All ER 402, it was held there was no direct evidence that the deceased passenger knew how much the driver had had to drink, so there was no deduction for contributory negligence. Some might say that was a little rum (groan) since it appears that 6 men including the passenger who was later killed when ejected from the car, travelled together, drank together at pubs between 12.30pm and 3.30pm (the driver admitted to drinking 4 pints of lager) and then again shortly before the accident at 8.15pm (the driver admitted to drinking 3 half pints). By backward calculation, the driver’s alcohol reading was 148mgs in 100 ml of blood (not quite twice over the limit).
The surviving 4 passengers all gave evidence that they did not think the driver was in any way unfit to drive and none would admit to knowing how much the driver had had to drink.
The requirement of knowledge seems to have been overemphasised in this case.
But in Green v Gaymer Lawtel 25/06/1999 the passenger again gave evidence that he did not know how much the driver, who was with him in the pub, had to drink and he did not form the impression from his behavior that he was drunk. It was accepted that the passenger had only one pint to drink. Another witness who was at the pub also confirmed that he did not believe the driver to be drunk or materially impaired by drink, However the publican gave evidence that the driver had in fact had at least 5 pints of cider (strength unreported) starting from 5pm (whereas the passenger arrived much later) and that in his opinion the driver was unfit to drive when he left the pub at 11.30pm.
Held: the Claimant must have been aware, by closing time, that the driver’s ability to drive was impaired. Deduction of 20% for contrib.
And what of the position where the passenger is in his cups, and like Manuel, knows nothing?
In Joslyn (2003) 214 CLR 552,the Australian High Court rejected the notion that there had to be actual knowledge, adding
“[T]he issue is not whether a reasonable person in the intoxicated passenger’s condition – if there could be such a person – would realise the risk of injury in accepting the lift. It is whether an ordinary reasonable person – a sober person – would have foreseen that accepting a lift from the intoxicated driver was exposing him or her to a risk of injury by reason of the driver’s intoxication”.
Booth v White 2003 EWCA Civ 1708, in which Julian Waters of these chambers appeared for the Defendant, makes the same point. The passenger’s conduct is judged by what a sober reasonable person in the position of the passenger would have done.
To be clear: The test is not what the Claimant knew. It is what he ought to have concluded which matters.