Loss of Chance and Causation
Losing chances: the High Court’s decision in Tabet v Gett  HCA 12 and the renewed focus on causation
The High Court’s decision in Tabet v Gett  HCA 12 was handed down on 21 April 2010. This case creates a fundamental change in the way many injured patients will be able to sue their doctors for medical negligence. It has rejected the proposition that an injured patient can recover damages where, by reason of the doctor’s negligence, the patient has lost a chance to be cured or to have a better medical outcome when that chance is less than 51%.
Since Naxakis v Western General Hospital  HCA 22, a series of lower court decisions have left the entitlements of patients and the obligations of doctors and their medical indemnity insurers in these circumstances uncertain. In upholding the NSW Court of Appeal’s finding that the causal effects of the clinical negligence of a medical practitioner should be assessed on the balance of probabilities alone rather than “on the basis of loss of a chance of a better outcome” the High Court decision has finally settled the matter.
While this decision can be seen as a win for medical indemnity insurers, the broader implication of this and other recent High Court’s judgments, is likely be a renewed focus by defendant lawyers on causation defences in personal injury claims. The trend in recent High Court judgement is sending a message that the burden of proof required to establish causation must be respected and will not be easily satisfied.
What is Òloss of a chanceå?
Question: What happens when a medical practitioner fails to diagnose a patient’s medical condition in circumstances where a reasonable and competent medical practitioner exercising due care and skill would have diagnosed and commenced treatment for that condition? Answer: Easy, the medical practitioner is prima facie negligent.
But medicine is not an exact science, and there is no magic wand. What happens then, if the accepted treatment that would and should have been administered upon diagnosis, would not necessarily have made a difference in the patient’s overall outcome? What if there was only a chance of a better outcome? And what if that chance was less than 51% likelihood?
Has the patient lost something of value? The majority of people would undoubtedly say yes. Is that Òsomething of valueå a legally actionable damage in a claim for compensation? The High Court this week has said no.
The facts: Tabet v Gett
Six year old Reema Tabet suffered a seizure in hospital on 14 January 1991 as a result of raised intracranial pressure, itself a result of an undiagnosed brain tumour. She was left with irreversible brain damage.
The previous morning, a nurse observed Reema to be unresponsive and staring. After a 36 day trial, Studdert J found that Dr Gett, a specialist paediatrician, should have ordered a CT scan upon being advised of the nurse’s observations. Had a scan been performed that day, the brain tumour would have been detected and treatment, most likely the administration of steroids, would have been instituted that morning. The finding of a negligent omission was not in issue before the High Court.
Had Dr Gett ordered a CT scan on the morning of 13 January, the trial judge found that there was a 40% chance of avoiding the seizure and deterioration of her condition on 14 January. This was later reduced to a finding of 15% by the New South Wales Court of Appeal. 
The contribution of the seizure event on 14 January 1991 to Reema’s overall disabilities was held by the trial judge to be 25%, with the rest of her disabilities being partly a result of the tumour, partly because of the surgery to remove the tumour, and partly because of the subsequent radiotherapy.
The question before the High Court was whether the common law of Australia should recognise the loss of a chance of a better outcome, in cases where medical negligence has been found, as an actionable damage. The chance lost by Dr Gett’s negligence, as submitted on behalf of Reema Tabet, was the chance of avoiding so much of the eventual outcome (25% of her disabled state) as was attributable to her seizure and deterioration on 14 January 1991.
Causation and damage
Two essential elements of an action in negligence are (a) proof of damage, and (b) the causal link between the plaintiff’s damage and the defendant’s breach of duty.
The High Court described these elements as requiring satisfaction that, according to the course of common experience, the more probably inference appearing from the evidence is that a defendant’s negligence caused the injury or harm. ÒMore probableå means no more than that, upon a balance of probabilities, such an inference might reasonably be considered to have some greater degree of likelihood; it does not require certainty.
If the chance that is lost is no greater than a 50% likelihood of a better outcome, then the defendant’s negligent act or omission cannot be said to have caused, on the balance of probabilities, the plaintiff’s damage (being the physical illness or injury). To address this hurdle, Òloss of a chanceå claims have seen plaintiffs arguing that the lost chance itself, rather than the physical illness or injury, is to be regarded as the Òdamageå caused by the defendants breach, and therefore should be compensable.
The level of confusion in these claims has been compounded by the subsequent attempts to quantify damages where the gist of the action is a lost opportunity. How does one value a chance or opportunity in monetary terms?
The Òall or nothingå’approach of the common law means that, once causation is proved on the balance of probabilities (greater than 50% likelihood), a plaintiff is then entitled to full recovery of the assessed damages for his or her loss.
In Òloss of a chanceå claims, various approaches to quantum have been postulated, including the Òall or nothingå approach, or awarding the plaintiff full damages if the 51% threshold is met while only to that percentage of the assessed damages if the loss of a chance is less than 51%,  or basing compensation on whatever be the percentage of the chance lost, whether above or below 50%. 
These contrasting obiter and/or subordinate court opinions have led to some creative pleadings and heated mediation arguments between medical negligence practitioners across the various state jurisdictions. The High Court’s settlement of the issues has been long awaited.
The loss of Òloss of a chanceå
In five separate, but unanimous judgments, the Justices of the High Court held that the law of negligence in Australia does not permit an action for recovery when the damage claimed can only be characterised as “the loss of a chance of a better outcome.” Questions of assessment of damages now fall away.
The Court held that rule requiring proof of damage on the balance of probabilities represents a striking by the law of a balance between the competing interests of the parties. The substitution of the loss of the chance as the actionable damage represents a shift in the balance towards claimants by replacing notions of probabilities with notions of possibilities. Any such fundamental change in policy, it was held, would more appropriately be the domain of Parliament.
Reema Tabet’s appeal was rejected as causation and damage could not be established to the requisite standard of proof.
Focusing on the burden of proof
Kiefel J noted in her judgment that the general standard of proof required by the common law and applied to causation is relatively low, requiring only probabilities and not certainties of proof that the breach was a cause of the plaintiff’s harm. But since the High Court’s oft quoted decision in March v Stramare (E&MH) Pty Ltd (1991) 171 CLR 506, the resolution of the question of causation by taking a Òcommon sense approachå which may be informed by Òvalue judgements and policy choiceså may be seen by some to have lowered the bar for plaintiffs in establishing that a defendant’s negligence conduct Òcaused or materially contributed toå the plaintiff’s loss.
A series of recent cases, commencing with Adeels Palace Pty Ltd v Moubarak  HCA 48 and C.A.L. No 14 Pty Ltd v Motor Accidents Insurance Board  HCA 47, and then followed recently with Amaca Pty Ltd v Ellis  HCA 5, have seen the High Court reverse this trend by repeatedly rejecting claims on the issue of causation where the evidentiary burden has not been met. The High Court has emphasised the need for positive evidence that the negligent act is a probable cause of the plaintiff’s harm, rather than indirect inferences drawn from population studies or bold assertions of scenarios which, according to Òcommon senseå Òmightå have made a difference to the plaintiff’s outcome.
Issues of causation have always been high on the radar for medical negligence practitioners, but often are seen as secondary to duty and breach considerations in non-medical personal injury claims.
Tabet and other recent cases indicate that the High Court has directed attention back to first-principles causation and the importance of meeting the burden of proof. Personal injury practitioners will need to ensure that a rigorous investigation and preparation of causation evidence becomes a primary focus of bringing, or defending, a negligence claim.
 Although the Court of Appeal set aside the decision of Studdert J, holding that no damages were available where the causal effects of the clinical negligence could not be proven on the balance of probabilities. These percentages were rejected by the High Court, which held that the evidence did no more than provide a basis for speculating that the chance of a better outcome was lost.
 Callinan J in Naxakis v Western General Hospital  HCA 22 at [129″130].
 Santow JA in Rufo v Hosking  NSWCA 391 at .
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