Collyer v Mid Essex Hospital Services NHS Trust

In a clinical negligence claim, a claimant must prove on the balance of probabilities both a breach of duty and that the negligent mechanism advanced caused the injury. Showing that a negligent explanation is the most likely among several possibilities is insufficient unless it is more likely than not that negligence caused the injury. Eliminating alternative explanations does not itself establish causation; the court must assess all the evidence as a whole. A rare or unexplained outcome does not create a presumption of negligence where both parties call evidence. A risk which is not a recognised complication does not require a warning merely because it is theoretically possible.

The claimant suffered near-total, permanent bilateral hypoglossal nerve palsy after life-saving laryngectomy for recurrent laryngeal cancer. He alleged that the surgeon negligently damaged both nerves during dissection or incorporated them into the sutures. The defendant relied on non-negligent explanations, including traction, tissue vulnerability, oedema, intubation and positioning.

The court determined whether negligence had been proved on breach and causation, whether the rarity of the injury supported an inference of negligence, and whether the risk required a warning.

1. The claim was dismissed. The claimant bore the burden of proving negligence and causation on the balance of probabilities. The court applied the Bolam standard: breach depended on whether the surgeon’s conduct accorded with a practice accepted as proper by a responsible body of relevant clinical opinion.

2. Under Rhesa Shipping Co S.A. v Edmunds and Fenton Insurance Co Ltd [1985] 1 WLR 948, where several possible causes exist, the claimant must establish that the negligent cause was more likely than not. It is insufficient merely to show that it was the most likely explanation. The court could conclude that the mechanism remained unexplained.

3. Consistently with O’Connor v The Pennine Acute Hospitals NHS Trust [2015] EWCA Civ 1244, excluding alternative causes did not itself prove the claimant’s case. The court had to step back and assess whether the alleged negligent mechanism was established on all the evidence.

4. The rarity of the injury did not create a presumption of negligence. Ratcliffe v Plymouth and Torbay Health Authority; Exeter and North Devon Health Authority [1998] PIQR 170 showed that even an extremely rare or unexplained outcome requires careful evaluation and may be consistent with proper care.

5. The court found that the injury probably occurred during surgery, but rejected the proposed suture-inclusion mechanism as implausible and found partial bilateral transection during dissection no more likely than not. Traction and anaesthesia-related pressure were possible, but remote or highly unlikely explanations. Hypoglossal nerve injury was not a recognised complication of laryngectomy, so failure to warn of it was not negligent.