Medical negligence litigation is unlike litigation generally. The cases throw up arguments about causation the like of which do not appear elsewhere.
In Bailey v The Ministry of Defence & Anor.  EWCA Civ 883, the plaintiff suffered brain injury due to hypoxia. She was in the care of the defendants and suffered a heart attack when she aspirated her vomit. The heart attack deprived her of oxygen.
She had been very ill for some time. The illness reduced her capacity to deal with the vomiting.
The defendants denied that the plaintiff, in her litigation, had proved that anything they did or failed to do had caused her injury.
In fact the trial judge had found:
“One component was the weakness engendered by the pancreatitis, the other was the weakness engendered by the consequences of the negligence on 11 – 12 January, which led to a very stormy passage for the Claimant ending (purely from a surgical point of view) on 19 January when the packing of the liver was removed. Even leaving out of account the independent effect of the pancreatitis, it defies all common sense to say that she had recovered from the effects of all that by 26 January. I am satisfied, on the balance of probabilities, that she had not and that she was weakened as a result.”
The immediate cause of her injury was aspiration of the vomit; however she had been weakened and her cough reflex was unable to deal with that. The weakness followed from, inter alia, acts of negligence occurring during her care by the defendants.
The court in finding that this had contributed materially to the immediate cause of the injury found for the plaintiff against the defendant.