Australia: Pre-existing Conditions - Principles of Causation Revisited

Curwoods Case Note
Last Updated: 18 February 2012
Article by Joseph Vermiglio and Andrew Gorman

Judgment date: 6 February 2012

Ridolfi v Hammond [2012] NSWCA 31

New South Wales Court of Appeal

In Brief

  • Where competing medical opinions arise in relation to the role of a pre-existing condition, considerable weight should, ordinarily, be attached to those of doctors who treated a claimant prior to the accident.
  • In determining whether a defendant has discharged its evidential onus of disentanglement of pre-existing conditions, the court is required to evaluate possibilities, not proof on a balance of probabilities.


On 28 August 2000, the plaintiff was injured when his stationary vehicle was rear ended at high speed. He suffered a whiplash injury. Two months after the accident, the progressive neurological condition known as myelomalacia was diagnosed. In issue was the cause of that condition, on a background of pre-existing disc disease.

Prior to the accident the plaintiff had planned to operate a Bed and Breakfast venture. On account of his injuries, this did not eventuate and he was granted a disability pension in 2004.

District Court Decision

Gibbs DCJ held that the underlying condition, in the absence of surgical intervention, would inevitably progress to the point where the plaintiff would be unable to work. Her Honour held the plaintiff's refusal to undergo surgery was relevant as to the only opportunity available to halt the inevitable decline in his condition.

The trial judge found that there was an exacerbation of the underlying cervical spondylosis which rendered the plaintiff totally incapacitated for a period of 8 years after the accident, up until the plaintiff refused to undertake corrective surgery. After this time, her Honour held that the pre-existing condition subsumed the consequences of the accident.

Her Honour rejected the submission that the accident precipitated myelomalacia on a number of grounds. First, the plaintiff exhibited signs of neurological deficit before the accident and the treating doctor, Dr Presgrave, reported before the accident that there was a reasonable likelihood that the plaintiff might require surgical management in the future.

Secondly, Dr Presgrave's 2002 report, in which he concluded that the cervical canal stenosis "might have become symptomatic with the passage of time, or for example, in the event of cervical injury" was afforded little weight as it contained "fundamental errors in his starting assumptions". In particular, the statement that on examination the tendon reflexes were normal and there were no sensory abnormalities was inconsistent with Dr Presgrave's identification of brisk reflexes in the lower limbs in August 1998 and in the upper limbs in February 1999.

Court of Appeal

The Court of Appeal held that the primary judge erred when she rejected the submission that the accident caused the onset of myelomalacia on the basis that Dr Presgrave's report, in support, contained a fundamental error. The opinion of a doctor who treated a patient prior to the accident should be given greater weight than the trial judge afforded.

In determining the burden of proof, the Court of Appeal restated the principles deduced in the High Court decision of Purkess v Crittenden2 :

"The defendant has the burden of adducing evidence to show that the incapacity would have come about independently of the accident, for example by reason of a pre-existing degenerative condition. However, the burden of proving the balance of probabilities that the incapacity was caused by the accident always rests on the plaintiff."

However, the Court of Appeal noted that the principles must be understood in light of those stated in Malec v JC Hutton Pty Ltd3 , which were summarised by Ipp JA in Seltsam Pty Ltd v Ghaleb4 :

  1. "In the assessment of damages, the law takes account of hypothetical
  2. situations of the past, future effects of physical injury or degeneration, and the chance of future or hypothetical events occurring.
  3. The court must form an estimate of the likelihood that the alleged hypothetical past situation would have occurred.
  4. The court must form an estimate of the likelihood of the possibility of alleged future events occurring.
  5. These matters require an evaluation of possibilities and are to be distinguished from events that are alleged to have actually occurred in the past, which must be proved on a balance of probabilities".

The Court of Appeal quoted Ipp JA [at 104] in Seltsam Pty Ltd v Ghaleb for the distinction between the relevant tests of possibilities with that of the balance of probabilities:

"Where a defendant alleges that the plaintiff suffered from a pre-existing condition, the evidential onus as explained in Watts v Rake and Purkess v Crittenden remains on the defendant and must be discharged by it. Nevertheless, to the extent that the issues involve hypothetical situations of the past, future effects of physical injury or degeneration, and the chance of future or hypothetical events occurring, the exercise of "disentanglement" discussed in those cases is more easily achieved. That is because the court is required to evaluate possibilities in these situations - not proof on a balance of probabilities".

The Court of Appeal held that the trial judge erred in undertaking the evaluation the balance of probabilities. Her Honour treated the progress of the degenerative condition as an event which actually occurred (to be determined on the balance of probabilities) rather than as a hypothetical past situation (to be assessed by reference to possibilities and probabilities).

The evidence on the whole was inconsistent with the primary judge's findings relating to both causation and the subsuming of the pre-existing condition.
In allowing the appeal, the court held that the plaintiff was entitled to damages beyond the date upon which he declined to undertake corrective surgery following a finding that such surgery was unlikely to completely relieve his symptoms. He was entitled to ongoing economic loss reflecting the assessment of his pre-accident earning capacity, albeit with a reduction of 40% for vicissitudes instead of the customary 15%.


The case serves as a useful reminder of the following principles of causation:

  1. If a plaintiff proves that he was incapacitated as a result of the injuries he sustained in an accident, he or she is entitled to damages in respect of the incapacity. The plaintiff's entitlement is not reduced because he or she had a pre-existing condition which made the consequences of the accident more severe than if that condition had not been present.
  2. In determining liability for negligence, the plaintiff always bears the onus of proving, on the balance of probabilities, any fact relevant to the issue of causation.
  3. Where the plaintiff establishes a prima facia case, that the incapacity has resulted from the injuries sustained in the accident, the defendant has the burden of adducing evidence to show that the incapacity would have come out independently of the accident, for example by reason of a pre-existing degenerative condition.
  4. The court is required to undertake the disentanglement exercise by reference to an evaluation of possibilities, not proof on the balance of probabilities.

Where there is an issue about the role played by a pre-existing condition, it is important for insurers to obtain expert medical opinion formulated by reference to the above principles.


1 Beazley JA, Handley AJA and Sackville AJA
2 [1965] HCA 34
3 [1990] HCA 20
4 [2005] NSWCA 208

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