Articles and Case Studies

Complexity of Causation

07 Dec 2012

by Enore Panetta

In 2006 the plaintiff, Mrs Paul, underwent coiling for an aneurysm in her right anterior cerebral artery. During the procedure, the aneurysm ruptured, as a result of which she suffered a stroke and sustained permanent disabilities.


The defendant, a radiologist, was not involved in the 2006 procedure, but in 2003 had reviewed and reported on a cerebral angiogram performed on the plaintiff, when he negligently failed to detect the presence of the aneurysm.

The plaintiff sought to recover from the defendant damages for the injuries she sustained in 2006, alleging that his negligence in 2003 caused the injuries that she suffered in 2006.

Breach of duty was admitted.

The plaintiff alleged that, if the defendant had diagnosed her aneurysm in 2003, she would have obtained treatment for it then, and that had she done so then (on the probabilities) the aneurysm would have been permanently obliterated, without any adverse consequence. She would have avoided the rupture and the consequential injuries she suffered.

The defendant submitted that his duty of care did not extend to taking reasonable care to avoid harm occasioned by treatment of a diagnosed condition. The loss and damage suffered by the plaintiff was not caused by his admitted breach of duty. The rupture was an inherent risk of the coiling procedure.


Factual causation

In this first aspect of the court’s inquiry into causation, the court compared what would have occurred if the plaintiff’s aneurysm had been diagnosed in 2003 with what in fact occurred in 2006.

The court had no doubt that the plaintiff would have had treatment in 2003 had the defendant diagnosed the aneurysm then. More probably than not, she would have acted on the advice of her treating doctors as to the procedure to be undergone and would have had the aneurysm treated by clipping (the preferable option in 2003). She would have accepted the associated risks of intra-procedural rupture (5-10%) and consequential stroke (5%). The probabilities were overwhelmingly against those risks materialising.

On the probabilities, therefore, but for the defendant’s negligence, the aneurysm would have been obliterated by clipping in 2003 without rupture. She would not have suffered the stroke and the consequent disabilities.

Factual causation was therefore established.

Scope of liability

The more complicated aspect was the scope of liability element of causation.

The scope of liability inquiry involves a policy judgment as to whether it is appropriate, having regard to the relevant circumstances, for the defendant’s liability to extend to the harm in question. For this purpose the court must consider (amongst other things) why responsibility for the harm should be imposed on the defendant.

The court stated that the duty of care in the diagnosis of suspected aneurysms serves to enable an aneurysm, once diagnosed, to be treated, in particular to remove the risk that it will spontaneously rupture. Harm from spontaneous rupture was harm of the kind from which the relevant duty of care was intended to protect the patient. However, the very treatment that diagnosis would enable — whether clipping or coiling — itself carried risks, including of intra-procedural rupture. Harm occasioned by the materialisation of those risks was not harm of the kind from which the relevant rule of responsibility was intended to protect.

The exposure to the risk of intra-procedural rupture had nothing to do with the defendant’s failure to diagnose the aneurysm. It was a consequence of the aneurysm being diagnosed, whenever it was diagnosed.

Accordingly, scope of liability was not satisfied and there was judgment for the defendant.

Enore Panetta is a partner at  Panetta McGrath Lawyers.

1 Paul v Cooke [2012] NSWSC 840

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