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Legal Concepts · Professional Negligence
Causation is the legal requirement that a professional’s breach of duty must have actually caused your loss. Australian courts use two tests: the but-for test (would the harm have occurred without the breach?) and, where that test fails, the material contribution test. Both are codified in civil liability legislation across every Australian state and territory.
There is a particular kind of frustration that comes when a professional has clearly let you down — you can see it, your records show it, the timeline tells the story plainly — and then someone tells you that might not be enough. That the law requires something more. That “causation” needs to be proved.
It is a legitimate concern, and it is worth understanding properly. Causation is the legal link between what the professional did wrong and the loss you suffered. Without it, even clear-cut negligence will not translate into a successful claim. But it does not have to be as daunting as it sounds — and for most people who have genuinely been harmed by a professional’s failure, causation can be established with the right approach and the right evidence.
Causation is the third of four elements that must be established in any professional negligence claim — the others being duty of care, breach of duty, and loss. It answers a simple but critical question: did the professional’s failure actually cause the harm you experienced?
Here is why it matters. Imagine a solicitor who fails to advise you about a particular risk in a contract — that is a clear breach of duty. But if that risk would never have materialised regardless of the advice, you have not actually suffered a loss from the breach. The failure happened; the consequence did not flow from it. Causation is the bridge between those two things.
Australian courts require that the connection between the breach and the loss be more than coincidental. It has to be established, on the balance of probabilities, that the professional’s negligence was an actual cause of what happened to you. This approach is codified in legislation across every Australian state and territory — and it gives rise to two distinct tests that courts apply depending on the circumstances.
Primary causation test
The starting point in almost every negligence case is the but-for test: but for the defendant’s negligence, would the harm have occurred?
If the answer is “no” — the harm would not have occurred without the professional’s failure — causation is established. If the answer is “yes” — the same outcome would have resulted even if the professional had acted correctly — causation fails.
This test is codified under section 5D(1)(a) of the Civil Liability Act 2002 (NSW), which requires that the negligence be a necessary condition of the harm. Equivalent provisions exist in every other Australian jurisdiction: section 11 of the Civil Liability Act 2003 (QLD), section 51 of the Wrongs Act 1958 (VIC), section 5C of the Civil Liability Act 2002 (WA), section 34 of the Civil Liability Act 1936 (SA), section 13 of the Civil Liability Act 2002 (TAS), section 45 of the Civil Law (Wrongs) Act 2002 (ACT), and section 13 of the Personal Injuries (Liabilities and Damages) Act 2003 (NT). These provisions were all introduced following the 2002 Ipp Review — the Review of the Law of Negligence Final Report — which recommended a nationally consistent codification of the causation test.
The High Court of Australia confirmed in March v Stramare (E & MH) Pty Ltd (1991) 171 CLR 506 that the but-for test should not be applied mechanically. The majority affirmed a commonsense approach to causation — courts ask what the evidence shows about real-world connections between conduct and outcomes, not just whether a logical formula is satisfied.
A practical example: a financial adviser recommends a high-risk investment portfolio that does not match your risk profile or financial goals. The market turns and you suffer significant losses. The but-for question is: would you have suffered those same losses if the adviser had given you proper, appropriate advice? If proper advice would have steered you to a safer investment, causation is established. If the same losses would have occurred regardless — because the entire market collapsed in a way no strategy could have avoided — causation becomes much harder to establish. That last scenario is exactly the kind of argument defendants and their insurers will run.
When multiple causes are involved
The but-for test does most of the work in most cases. But it has a known limitation: it struggles in situations involving multiple contributing causes. If more than one factor caused the harm and the professional’s negligence was only one of several, a purely mechanical but-for analysis can produce unfair results.
Australian courts have addressed this through the material contribution test. Where multiple factors contributed to a harmful outcome, a defendant may still be liable if their negligence materially contributed to the risk of harm, or to the harm itself — even where that contribution was not the sole cause.
The origins of this approach lie in Bonnington Castings Ltd v Wardlaw [1956] AC 613, where the House of Lords held that a defendant could be liable even where their breach was one of several contributing causes. Australian courts have adopted and developed this principle in the decades since. The High Court addressed causation in multi-factor scenarios in Amaca Pty Ltd v Ellis (2010) 240 CLR 111, emphasising that causation remains a question of fact informed by commonsense and the totality of the evidence — not satisfied by mere possibility or statistical inference.
In practical terms, this test most commonly arises in medical negligence claims. A patient who receives a delayed diagnosis may argue that the delay materially contributed to the worsening of their condition — even if the condition would have progressed to some degree regardless. A doctor cannot escape liability simply by pointing to the underlying disease if their failure to act in time made things significantly worse.
This is one of the most contested and technically demanding aspects of professional negligence litigation. If your situation involves multiple possible causes of loss, specialist advice is essential.
Proving factual causation — establishing that the negligence was a necessary condition of the harm — is the first limb of the test. But it is not the whole inquiry.
Section 5D(1)(b) of the Civil Liability Act 2002 (NSW), and its equivalents in other states, adds a second limb: courts must also be satisfied that it is appropriate for the scope of the negligent person’s liability to extend to the harm so caused. This is often called normative causation or the scope of liability question.
In plain English: even where the professional’s failure factually caused a loss, the court asks whether it would be fair and reasonable to hold them responsible for this particular type of harm in these particular circumstances. Not every factual consequence of negligence attracts legal liability.
The High Court addressed this directly in Adeels Palace Pty Ltd v Moubarak (2009) 239 CLR 420, confirming that both limbs must be satisfied — factual connection alone is not sufficient. For most professional negligence claims, the normative question resolves in the claimant’s favour because the harm is exactly the type of harm the professional’s duty was supposed to prevent.
The application of causation looks different depending on the type of professional involved. These are the scenarios our team deals with most often.
If your solicitor missed a limitation period, courts must assess what your original claim would have been worth and whether you would have succeeded — a “case within a case.” This requires expert legal analysis of both the procedural failure and the underlying merits of the lost claim. Solicitor negligence claims are among the most technically demanding to run, and causation is often where they are hardest fought.
Did the misdiagnosis or treatment failure cause your condition to deteriorate beyond what would have happened with proper care? Medical expert evidence comparing actual outcomes against appropriate clinical management is central. Where conditions are time-sensitive — as many are — causation can often be established clearly.
Would you have suffered the same financial losses if you had received appropriate, suitable advice? This requires evidence of what a properly advised investor in your circumstances would have done, and what outcomes that strategy would have produced. Market conditions, timing, and the specific nature of the advice all feed into this analysis.
If your accountant’s error triggered an ATO audit, a tax penalty, or an incorrect financial position, causation often turns on whether correct advice or returns would have produced a different outcome. For most accounting errors, the consequences are direct and traceable — and causation can be established clearly.
Establishing causation is not something that happens by assertion. It requires evidence — and in most cases, expert evidence. Courts assess causation on the balance of probabilities: more likely than not. That is a meaningful and achievable standard with the right support behind you.
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Independent expert opinion
A qualified professional in the same field as the defendant, providing an independent opinion on whether the conduct fell below the proper standard and how the failure produced the outcome claimed.
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Contemporaneous records
File notes, correspondence, medical records, financial statements — documents that trace the timeline and establish precisely what happened, and when.
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Counterfactual analysis
A reasoned, evidence-based account of what would most likely have occurred if the professional had acted correctly — the core of any causation argument.
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Financial modelling or actuarial evidence
In cases involving investment losses, lost earnings, or long-term financial consequences, quantitative expert analysis is often required to demonstrate and value the loss.
In most Australian states, professional negligence claims must be commenced within 3 years of the date you became aware — or should reasonably have become aware — of the negligence. In some states, a longer general limitation period may apply, but earlier time limits often govern personal injury claims. Missing this deadline can permanently extinguish your right to claim. If you are unsure whether your time has run, contact our team for a free assessment as soon as possible.
People often assume that proving negligence is the hard part — and it can be. But for experienced professional negligence lawyers, establishing breach of duty is often more straightforward than it might seem. Causation is where cases more frequently succeed or fail.
The inherent difficulty lies in counterfactual reasoning: courts must decide what would have happened in a world where the professional did not make the mistake they actually made. That world does not exist. It has to be constructed from evidence, expert opinion, and reasoned inference.
Defendants and their professional indemnity insurers know this. Their legal teams will often concede breach — or at least not fight hard on it — and concentrate all their effort on causation. They will argue that the same loss would have occurred anyway. They will challenge the assumptions in your expert’s analysis. They will look for intervening causes and alternative explanations.
This is not a reason to be discouraged. It is a reason to have specialist legal representation from the start. Our team understands how causation arguments are built — and how they are attacked. The free case evaluation is designed precisely to give you an early, honest assessment of where causation stands in your particular situation.
Causation is a complex legal question. Whether your loss is legally connected to a professional’s failure depends on the specific facts of your situation and requires careful legal analysis. Our specialist professional negligence lawyers can assess your situation and advise whether you have a viable claim.
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Common questions
The but-for test asks whether the harm would have occurred but for the defendant’s negligence. If the answer is no — meaning the harm would not have happened without the professional’s failure — factual causation is established. It is the primary causation test under civil liability legislation in every Australian state and territory, applied with commonsense rather than mechanically, as confirmed by the High Court in March v Stramare (E & MH) Pty Ltd (1991) 171 CLR 506.
Where several factors contributed to your loss, the but-for test may be difficult to satisfy in its strict form. In those circumstances, Australian courts may apply the material contribution test, which allows a defendant to be held liable if their negligence materially contributed to the risk or the outcome — even if it was not the sole cause. This is a complex and contested area of law and requires specialist legal advice tailored to the specific facts of your situation.
In medical negligence, causation requires establishing that the clinician’s failure — the misdiagnosis, delayed treatment, or procedure that went wrong — caused your condition to worsen or your health outcome to be materially worse than it would have been with proper care. This almost always requires independent medical expert evidence comparing what actually happened against what appropriate clinical management would have produced. Where conditions are time-sensitive, causation is often capable of being established clearly.
Factual causation asks whether the negligence was a necessary condition of the harm — the but-for question. Normative causation is the second limb of the test: courts ask whether it is appropriate, given the circumstances, for legal liability to extend to the harm that resulted. In most professional negligence claims, once factual causation is established, the normative question resolves in the claimant’s favour. It becomes more significant in cases involving unexpected consequences or remote outcomes.
Yes. Australian courts assess causation on the balance of probabilities — which means more likely than not. You do not need to prove causation to a certainty, and you do not need to eliminate every other possible cause. You need to establish, through evidence and expert analysis, that the professional’s failure was probably a cause of your loss. That is a meaningful and achievable standard, particularly with the right legal and expert support.
Material contribution refers to a defendant’s contribution to either the risk of harm or the harm itself being substantial enough to attract legal liability — even where that contribution was not the only cause. It is particularly relevant where multiple factors combined to produce the harmful outcome. The test originates from Bonnington Castings Ltd v Wardlaw [1956] AC 613 and has been adopted in Australian professional negligence litigation, particularly in medical negligence matters.
Our goal is to help people in the best way possible. this is a basic principle in every case and cause for success. contact us today for a free consultation.
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