In the recent case of Graves v Brouwer, at the first hearing the judge decided that the house fire was caused by an escape from a fire, deliberately lit by the defendant, in an alleyway between two houses, but decided that the defendant was not negligent. There were two competing theories on causation of the house fire (flying embers from the alleyway fire or arson). Arson was not investigated or properly considered and neither were other possible causes, such as smoking materials or cooking and heating appliances.

The Court of Appeal held that the judge mistakenly regarded one single answer from the defendant’s expert as crucial on causation. The particular answer had been in response to questions that ought never to have been put to an expert as they invited him to express a view on a conclusion of mixed fact and law whereas such matters were for the judge to decide. Also, the questions were based on a false premise: that if arson was excluded then by definition the alleyway fire had to be regarded as, on the balance of probabilities, the cause of the house fire.

The court dismissed the appeal, upholding the judge’s dismissal of the claim, but overturned the finding on causation. The court decided that the judge had not applied the proper test on causation, namely whether she was satisfied that the suggested explanation was more likely than not to be true. She did not have regard to the significant gaps in the court’s knowledge due to the lack of any adequate forensic investigation in the immediate aftermath of the fire.

This is a reminder of the importance of expert evidence when establishing causation in a negligence claim, particularly where there are a number of possible causes. If the state of the evidence is unsatisfactory, the claimant may be unable to prove the case on the balance of probabilities, even if detailed expert evidence has been submitted. It also provides an example of the court’s application of the principles in Rhesa Shipping Co SA v Edmunds (The Popi M) [1985] (where the House of Lords considered how a court should rule on causation when none of the factual scenarios suggested to it seem inherently likely).

Chris Harper is a partner and head of the dispute resolution team in Exeter. He specialises in commercial litigation and is named as a leader in his field by independent guides to the legal profession Legal 500 and Chambers. To contact Chris please call 01392 210700 or email