When someone suffers a poor medical outcome — whether during treatment, surgery, diagnosis or follow-up care — it is natural to wonder whether something went wrong. In NSW, patients may be entitled to compensation if their injury was caused by negligent medical treatment. One of the most important, and often misunderstood, legal questions in these cases is causation.
This article explains what causation means, why it is often the hardest part of a medical negligence claim, and how it can affect your right to compensation.
What is Causation?
In any negligence claim, a plaintiff must prove three things:
- A duty of care existed.
- The duty was breached (the care fell below a reasonable standard).
- The breach caused the injury — this is causation.
While proving a breach is often challenging, causation is usually the most contested element in medical negligence. It requires showing, on the balance of probabilities, that the negligence made a difference to the outcome.
Put simply: Would the injury have occurred anyway, even if the medical professional had acted properly?
If the answer is “yes”, the claim may fail — even if the care was below standard.
Why Causation is Difficult in Medical Negligence
Medical outcomes are rarely simple. Several factors often contribute to an injury, and distinguishing between natural progression and negligent treatment can be complex.
1. Multiple Possible Causes
A patient may also have underlying health conditions, unrelated complications, or inherent risks associated with the treatment. Courts must decide whether negligence was a material cause of the harm, not merely one possibility.
2. Reliance on Expert Medical Evidence
Causation is established through specialist medical opinions. Experts must explain how the negligent act caused, worsened, or failed to prevent the injury. Without clear expert support, a claim will struggle.
3. “Loss of Chance” Is Limited in Australia
Unlike some overseas jurisdictions, Australian courts do not generally award damages for the mere “loss of a chance” of a better medical outcome. Plaintiffs must still prove the negligence probably caused the injury — not just that it reduced their chances of avoiding it.
4. Intervening Events
Sometimes another event may “break the chain” of causation. For example, a patient’s unrelated medical deterioration or unexpected complication may sever the causal link.
5. The Injury Must Be “More Likely Than Not” Caused by the Negligence
If expert evidence only shows a possibility rather than a probability, causation is not met.
These principles, discussed across leading legal commentary including Precedent (AULA, 2023), demonstrate why medical negligence claims depend heavily on detailed evidence and expert analysis.
How Causation Affects a Plaintiff’s Personal Injury Claim
1. It Determines Whether a Claim Can Succeed
Even if the treatment was negligent, you must prove the negligence caused your harm. Without this link, a court cannot award compensation.
2. It Influences the Amount of Compensation
If only part of the injury was caused by negligence — for example, a pre-existing condition worsened by poor treatment — compensation may be apportioned accordingly.
3. Early Evidence Gathering Is Crucial
Medical experts, hospital records, imaging, and timelines all help establish causation. The earlier the investigation begins, the stronger the evidence tends to be.
4. It Shapes the Valuation and Settlement Strategy
Where causation is uncertain, insurers often dispute liability. Understanding the medical evidence allows your legal team to provide clear advice on risks, settlement ranges, and the merits of proceeding to court.
5. It Interacts With Other Personal Injury Schemes
For example, in NSW motor accident claims under the Motor Accident Injuries Act 2017, an injured person must prove that their injury was caused by the accident. If negligent treatment worsens the injury, the insurer may argue the medical negligence — not the crash — caused certain losses.
Causation becomes critical for defining what losses are recoverable.
Examples of Causation Issues in Medical Negligence
These common scenarios show how causation works in practice:
- Delayed diagnosis: If a cancer diagnosis was delayed, the patient must show the delay — rather than the underlying disease — worsened their prognosis.
- Surgical error: If a surgical mistake causes nerve damage, causation is usually clearer because the link is direct.
- Failure to warn: If a doctor fails to warn about a known risk, but the adverse outcome was that very risk, causation requires showing the patient would have declined the procedure had they been properly warned.
- Inadequate post-operative care: Plaintiffs must prove the negligence, such as failing to detect complications, caused the deterioration.
What This Means for Injured Patients
For anyone considering a medical negligence claim, understanding causation is essential. It is not enough to show that treatment was sub-standard. You must show that it probably caused your injury.
Key points to remember:
- Poor treatment alone does not automatically create liability.
- Strong medical evidence is central to success.
- Early legal advice helps identify whether causation is likely to be proven.
- Claims involving complex medical histories require particular care.
- A well-prepared case can overcome causation challenges with the right evidence.
How BPC Law Can Help
Medical negligence cases require meticulous investigation and careful handling of expert evidence. At BPC Law, our accredited specialists and senior personal injury lawyers have decades of experience running complex medical negligence and personal injury claims in NSW.
We give clear, practical advice about the strength of the causal link in your case, what evidence is required, and your prospects of success. Our focus is ensuring you receive the compensation you deserve — and helping you navigate what can be a medically and legally challenging process.