If a duty of care has been breached it means that the D has fallen below the standard of behaviour expected in someone undertaking the activity concerned. In Donoghue v Stevenson, the D breached his duty when he allowed a snail to get into the C's drink.
In each case, the standard of care expected is an objective one, where the D's conduct is tested against the standard of care which could be expected from a reasonable person (as in Blythe v Birmingham Waterworks). As it is objective, the D's own characteristics are often ignored like in Nettleship v Weston, where the court said that the D should have been as competent as the average driver, even though she was a learner.
Sometimes the D will be a child, in which case, the courts held that they are to be judged against a reasonable child of the same age. In Orchard v Lee, the court said that the boy who had engaged in 'horse play', accidentally knocking into a dinner lady, breaking her arm, had not breached his duty as he had reached the standard of a reasonable child.
Also where a particular D has a professional skill and the case involves the use of that skill, the court expects the D to show the degree of…