6.4 Causation
6.4.1 The conventional rule
The claimant has to show that but for the defendant's negligence he would
probably have avoided the injury and loss claimed. Thus lawyers often talk about
the 51% test' orproof on the balance of probabilities'. In the context of causation
they simply mean that the claimant will succeed if he shows that it is more likely
than not that the defendant's default caused the injury/loss.
Causation is an essential element of the tort of negligence. Beware of confusing
questions about whether causation has been established with questions about how
much the judgment should be for.
6.4.2 Loss of a chance
It is often asserted that damages for loss of a chance are not recoverable in the
English law of tort. This is untrue. In some commercial fields such damages are
regularly recovered [15]. But whether they can be or should be recoverable in
clinical negligence cases is contentious. The authority generally cited for the
proposition that such damages are not recoverable in tort isHotsonv.East Berk-
shire Health Authority 1987). ButHotsonsays nothing of the sort. The Court of
Appeal inHotsondecided that loss of a chance was damage which the law recog-
nised, and that accordingly to prove that one had lost a chance was to prove
causation. The Court of Appeal was anxious to avoid treating claimants who sued
in tort and in contract differently. Damages are uncontroversially recoverable for
loss of a chance in contract [16]. Why, the Court of Appeal said, should an NHS
patient who is deprived by a doctor's negligence of a chance of recovery, be
unable to recover damages, whereas the same patient, treated identically but pri-
vately and therefore under a contract) by the same doctor, be successful? The
court said that such an anomaly would be monstrous. The House of Lords never
decided the question of recoverability of damages for loss of a chance: it merely
decided that on the facts of that case it did not need to decide. The question is
still open.
Opponents of the extension to clinical negligence litigation of damages for loss
of a chance either rest their arguments on simple policy, or try to assert that in the
commercial field damages for lost chances are awarded when what has been lost is
the chance of obtaining a benefit rather than avoiding a detriment. This latter
assertion is difficult to sustain. Any half competent barrister can convincingly
frame the injury or loss in a clinical negligence claim as a lost benefit, and it is no
more difficult to prove a lost chance of avoiding a detriment than it is to prove a
lost chance of gaining a benefit.
It is arguable that in cancer cases the courts have been awarding damages for
loss of a chance [17]. But probably the better view is that these are not really loss of
chance cases at all.
Where damages for loss of a chance are recoverable, the lost chance does not
have to be greater than 50%: it simply has to be `real and substantial' [18].
Negligence 81