If we cannot establish that there has been a breach of duty then there can be no liability and the claim will fail at that stage but if a breach is established we need to go on to the next hurdle, which is to show that, but for that breach of duty, you would not have suffered your injury. In other words we have to show that the mistake made by the doctor actually caused your injury and that it was not some fluke of nature. This is “causation”.
It is often difficult to prove causation in medical negligence cases because, in most cases, the claimants were seeking medical treatment for something that was already wrong with them. That, of course, is why they were patients in the first place. Therefore, we have to consider what the position would have been had there been no negligence. In many cases defence experts will argue that the patient was doomed from the start and the mistake made no difference to the eventual outcome. We have to show that that is not right.
The Balance of Probabilities
The appropriate test to be applied in deciding whether or not an injury was caused by a breach of the duty of care is the “balance of probabilities” i.e. more likely that not. We do not have to establish anything to a scientific standard nor “beyond all reasonable doubt”. The court is concerned to establish the most likely explanation. Therefore, if there is a 51% probability that the injury was caused by the breach of duty and a 49% possibility that there was some other cause, then the court will conclude that it was caused by the breach. In other words, if there are a number of competing possible causes but one is more probable than any of the others, then the court will accept that as the cause.
It is also unnecessary for us to establish that the breach of duty was the sole cause (or even the main cause) of the injury. It is sufficient for us to establish that the breach made a material (i.e something more than just a purely nominal) contribution towards the injury even if there are other additional contributing causes.