Mansfield v Weetabix Ltd
Court of Appeal
Citations:  1 WLR 1263;  RTR 390;  PIQR P526; CLY 3765.
The defendant was unaware that he had a disease called malignant insulinoma. This disease can cause hypoglycaemic states where the individual’s blood sugar drops to dangerously low levels.
The defendant was driving when he entered a hypoglycaemic state. This caused him to drive erratically for a short period before crashing into the claimant’s shop and causing property damage. During the period in which he was driving erratically, the defendant was not aware that his driving was impaired. The claimant sued for negligence.
- What standard of care should be imposed on a driver who suffers from a physical illness?
The Court of Appeal held for the defendant. The standard of care should be modified in this kind of case to take into account the defendant’s unknown illness. A reasonable person in the defendant’s position would not have acted differently, so the defendant was not negligent.
This Case is Authority For…
Where the defendant is not aware that he has an illness which may cause him to harm others, he is held to the standard of a reasonable person who both has that illness and is not aware of it.
This case might appear to conflict with Roberts v Ramsbottom  1 WLR 823, where a sick defendant was held liable for injuring the claimant after he had a stroke behind the wheel. The Court of Appeal in Mansfield disapproved of, but did not overrule, Ramsbottom.
The Court of Appeal in Mansfield argued that the distinction between the two cases is as follows. The defendant in Mansfield had no reason to believe he was sick and lost the ability to appreciate that he was out of control once he became hypoglycaemic. By contrast, in Roberts, the defendant had warning signs that someone was wrong before he hit the claimant. He was aware that he did not feel well. Therefore, the defendant in Roberts should have stopped driving before he hit the claimant.
In any case, since Mansfield is a Court of Appeal decision and Roberts was a High Court case, Mansfield is the greater authority. If in doubt, apply Mansfield.