Australia: Possibilities, probabilities and pre-existing Injuries: a refresher on principles of causation

A common question in personal injuries matters is what impact, if any, a pre-existing condition suffered by a plaintiff will have on a plaintiff's damages claim. The NSW Court of Appeal recently considered whether an appellant's pre-existing neurological degeneration had subsumed the injuries sustained by him as a result of a motor vehicle accident, and thereby limited his entitlement to damages for economic loss.

Facts

The appellant was involved in a motor vehicle accident on 28 August 2000. Following the incident, imaging revealed spinal cord compression and myelomalacia (a pathological softening of the spinal cord). The appellant had suffered neck pain since 1997, and had had surgery in 1998 to treat degenerative disc disease. Despite this surgery, the appellant's degenerative disease was symptomatic up until the time of the motor vehicle accident.

There was a divergence in medical opinion as to whether the myelomalacia found after the motor vehicle accident was attributable to the underlying degenerative disease or the motor vehicle accident. The trial judge held that by 25 November 2008, the appellant's pre-existing condition had deteriorated to the point that it had overwhelmed the consequences of the motor vehicle accident. The trial judge highlighted the fact that the appellant had decided to not proceed with surgery to treat his condition, despite the opinion of numerous medical specialists.

Decision

The focus of the Court of Appeal was the question of whether there was a causal relationship between the accident and the appellant's ongoing neurological symptoms. In particular, the court considered the hypothetical situation of the likelihood of the injuries occurring in the absence of the accident in accordance with the principles espoused in Malec v JC Hutton Pty Ltd [1990] HCA 20. The court therefore looked at the matter in terms of possibility and probability, as opposed to strictly the balance of probabilities.

After a detailed discussion of the medical evidence, the Court of Appeal unanimously found that the trial judge erred by concluding that the consequences of the accident had been subsumed by the pre-existing condition. In the leading judgment, Justice Sackville considered that on the balance of probabilities the accident had caused stress to the appellant's spinal cord, which materially contributed to the appellant's spinal cord compression. Justice Sackville opined that the trial judge had not found that the appellant's unwillingness to undertake surgery had broken the chain of causation. However, he noted that in the event that she had, this finding was open to challenge given medical opinion that the surgery was not guaranteed to be successful and the significant risks of the procedure.

Justice Sackville accepted that in the absence of the accident, the pre-existing condition could possibly have led to the appellant being totally incapacitated from work in the future, however there was considerable uncertainty in determining the rate of deterioration. Accordingly, the traditional 15% reduction for the vicissitudes of life was increased to 40%.

Implications

This decision provides insight as to how a court will approach pre-existing injuries in terms of causation. While the specific impact of the accident on the appellant's health could not be precisely determined in light of the pre-existing injury, given that some impact on the appellant's condition was observed, the Court took a favourable stance in almost providing the appellant with the benefit of the doubt.

The Court's decision to increase the typical discounting for the vicissitudes of life represented a reasonable attempt to consider what likely long term impact the pre-existing would have had, but for the motor vehicle accident.

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