Burden of proof in product liability cases
The Court of Appeal has restated the established position that, where there are competing explanations for causation in an action for damages, the claimant must prove causation on the balance of probabilities and, if the claimant fails to do so, the court may find that the burden of proof has not been discharged and may therefore dismiss the action.
A claimant must convince the court that their version of events is more likely than not to have been the cause of the damage. The claimant must satisfy the following two tests:
that their version of events is more likely than any competing version of events; and
that it is not so inherently improbable that even if it is preferable to a competing version of events, it is still not enough to discharge the burden of proof.
That said, in some cases the court may ask “the single unitary question” and decide the case accordingly without having selected which of competing explanations is the more probable.
This is not a novel approach but is a reminder that where competing explanations for causation are put forward, claimants must ensure their evidence does not just provide a more probable explanation for the damage claimed than any other but that on the balance of probabilities it can explain it.
Where expert witnesses are instructed, their reports should address this issue with supporting evidence. It is not enough to say that the explanation they put forward is the least improbable. Other possible explanations should be tested, and suitable explanations given as to why they should be dismissed.