In professional negligence cases, it has long been established that the claimant in Scotland must prove three key points to demonstrate that the defender's actions were negligent. As we know, the test as set forward in the seminal Hunter v Hanley 1955 SC 200 case is:

(1) there is a usual and normal practice in such circumstances;
(2) the defender has not adopted that practice; and
(3) the course the defender adopted was one which no ordinarily skilled professional would have taken had he been acting with ordinary care.

However, what is sometimes forgotten is that this is not the only hurdle the claimant has to overcome to succeed in their claim. It is not enough that liability is established: in addition, the negligence must be the cause of the loss, both in fact and in law. In many cases, the action revolves solely around whether the pursuer's loss or injury was the direct result of the defender's negligence, i.e. whether causation has been established.

Factual Causation

Once the pursuer has proved the defender has been negligent, the next step is to demonstrate that this negligent act was the factual cause of the loss, known as the ‘but for’ test: ’but for’ the defender's negligence, the loss would not have occurred.

This may not be as straightforward to prove as it seems. In the leading case in the area of causation, Barnett v Chelsea and Kensington Hospital Management Committee [1969] 1 QB 428, it seemed undeniable that the defender had been negligent after a doctor sent the pursuer's husband home without examining or treating him. The pursuer's husband later died from poisoning. However, it was held that even though the hospital had been negligent in its care of the deceased, there was one element which meant the case failed: causation. The court found the deceased would have died as a result of the arsenic poisoning, regardless of any treatment which he may or should have received. In other words, the defender's negligence was not the factual cause of his death, and the defender could not be held liable.

The test was formulated in the context of medical negligence but applies across the board in professional negligence cases .The Barnett case demonstrates that even where negligence is proven – or admitted by the defender – this is by no means a guarantee that the claim will be successful.

The concept of reliance can be key in determining this issue in professional negligence cases. Did the claimant rely on the advice given by the professional? Would they have carried out the same course of action (which led to their loss), had non-negligent advice been provided? For example, in Shankie-Williams v Heavey [1986] 2 EGLR 139 it was established that a dry rot specialist had negligently stated in his report that there was no dry rot in a flat. However, the court held that the claimant purchasers had not shown that they had in fact relied on this report in purchasing the flat. There was therefore no causal link between the negligent report and the pursuer's subsequent loss, and the dry rot specialist was not held to be liable.

If the claimant cannot show that they would have carried out a different course of action had non-negligent advice been provided, than they will usually fail to get over the causation hurdle. We see this in cases against solicitors, surveyors, financial advisors and many other professionals. For example, in a case against their solicitor for a failure to advise of alleged access issues, can the aggrieved purchaser show what they would have done if they had been advised of the access problem? Would they have purchased the property anyway, on the same terms, because the access issue was not a big deal to them? In a claim by a lender against an alleged negligent surveyor, what would the lender have done had they known the “true” value of the property? Could it be that they would have nonetheless advanced the loan?

Legal Causation

It is also not enough for the claimant to prove that in fact, the defender’s negligence caused his loss. The final hurdle is legal causation – that the loss is sufficiently closely linked to the defender's negligence that they should be held liable. The courts will not always agree that just because the defender has been negligent, they have caused all loss resulting indirectly from that negligence.

For example, in McKew v Holland and Hannen and Cubitts (Scotland) Ltd 1970 SLT 68, the pursuer suffered an ankle injury due to the defender's negligence. He was later injured jumping down some steps, which he did to prevent himself falling when the ankle gave way. The pursuer claimed this was also caused by the defender's negligence. Yet the court found that although the defender had caused the original injury, they were not liable for the second. The negligence was not sufficiently close to the second injury that it could be the legal cause. The pursuer's actions meant that although the factual chain of events led from the initial negligence to the second injury, in legal terms this was not sufficient for the defender to be liable.


It is important for claimants and defenders alike to assess the strength of a professional indemnity case at the outset – not only in terms of the defender's alleged negligence, but also considering whether that negligence is factually and legally the cause of the pursuer's loss. The ’but for‘ test is a helpful general guide – would the pursuer have suffered this loss but for the defender's negligence?. If the answer to that question is ‘No’, the claimant can take the next step of assessing whether that cause is sufficiently close to the final loss that the defender will be held liable. This can be more difficult to determine, and ultimately may be a question for the court to decide. However, considering causation from the beginning of an action can mean fewer surprises later on; and means both parties may be able to take a view on settlement once negligence has been established.