Objective standard of care for a defendant with mental illness (Dunnage v Randall)

The standard of care in negligence is objective: the defendant's conduct is measured against that of the ordinary reasonable person, not against what this defendant personally could manage. In Dunnage v Randall [2015] EWCA Civ 673 the Court of Appeal held that a defendant suffering from mental illness is not judged by a lower, subjective standard. A defendant escapes liability only where his condition entirely eliminates his responsibility, so that his conduct was wholly involuntary. Where responsibility is reduced, even very substantially, but not wholly removed, he remains fixed with the objective standard. Childhood is the only category in which the comparator is moderated. Here the agreed evidence is that Gareth's control was very substantially impaired but not completely destroyed, and a reasonable person would not have handled petrol in this way. He therefore fell below the required standard and is in breach of duty to Leah.

Why A is wrong: Dunnage rejected a standard of the 'reasonable person with the same illness'; the comparator is the ordinary reasonable person.

Why B is wrong: Children are the one category for which the comparator is moderated; mental illness does not lower the standard.

Why C is wrong: Gareth owed Leah a duty of care as a visitor in his home; the issue is breach, not the existence of a duty.

Why D is wrong: Negligence does not require proof that the defendant knew his conduct was wrong; the test is objective failure to take reasonable care.