The objective test for contributory negligence. What is reasonable to invest in the reasonable person?

On 9 December 2015 the High Court delivered judgment in proceedings concerning a motor vehicle accident which occurred in the early hours of 12 March 2007 outside Port Victoria, South Australia.


Ms Danielle Chadwick was a rear seat passenger in a vehicle driven by Mr Allen when he lost control of the vehicle, left the roadway and struck a tree. Ms Chadwick was ejected from the vehicle and suffered serious spinal injuries.

Mr Allen and Ms Chadwick had been in an on/off relationship for a few years prior to the accident. They had been in each other’s company for the whole of the previous day, during which time Mr Allen and a friend had been drinking. It was apparent that he was intoxicated and indeed, at the time of the accident, Mr Allen’s blood alcohol concentration was 0.229g/100mL.

Between 1.30am and 2.00am on 12 March 2007, Mr Allen, Ms Chadwick and a friend decided to go for a drive – ostensibly to purchase cigarettes. At this stage, Ms Chadwick was driving. They were driving in and around the Port Victoria township for 10 to 15 minutes and were on an empty roadway when Ms Chadwick was forced to stop and answer the call of nature behind some bushes.

When she returned to the vehicle, Mr Allen had made his way into the driver’s seat. Ms Chadwick argued with Mr Allen and told him not to drive but he told her in no uncertain terms to get in the car.

Ms Chadwick gave evidence that she chose to get into the vehicle as it was dark and she believed she was otherwise to be left in the middle of nowhere. Against this, evidence was adduced that street lighting was observable 200 metres away and the hotel they had been drinking at was only 500 metres away.

Ms Chadwick eventually got into the rear driver’s side seat but Mr Allen accelerated hard even before Ms Chadwick could close the door. Mr Allen continued to drive erratically and aggressively and eventually lost control, striking two trees. Ms Chadwick had not fastened her seatbelt prior to the accident and was ultimately ejected from the vehicle, suffering significant spinal injuries.

Legislative frameworks

In South Australia such motor accident claims are brought pursuant to the Civil Liability Act 1936.


In a manner similar to the provisions of section 138 of the Motor Accidents Compensation Act 1999, section 47 of the Civil Liability Act 1936 (SA) creates a presumption of contributory negligence where an injured person relies on the care and skill of a person known to be intoxicated. It provides as follows:

(1) If—

(a) the injured person—

(i) was of or above the age of 16 years at the time of the accident; and

(ii) relied on the care and skill of a person who was intoxicated at the time of the accident; and

(iii) was aware, or ought to have been aware, that the other person was intoxicated; and

(b) the accident was caused through the negligence of the other person; and

(c) the defendant alleges contributory negligence on the part of the injured person, 

contributory negligence will, subject to this section, be presumed.

Whereas in NSW there is no fixed reduction for contributory negligence (section 138(3) providing that the damages recoverable “are to be reduced by such percentage as the court thinks just and equitable in the circumstances of the case”), section 47(3) imposes a standard reduction of 25%. Relevantly for the present case, section 47(5) increases that statutory reduction to 50% where the concentration of alcohol in the driver’s blood was greater than 0.15 g/100mL.

An exception is provided by section 47(2) in the following terms:

The injured person may rebut the presumption by establishing, on the balance of probabilities, that—

(a) the intoxication did not contribute to the accident; or

(b) the injured person could not reasonably be expected to have avoided the risk.

Again, this is comparable to the caveat in section 138(2)(b) which provides,

unless, in the circumstances of the case, the injured person or deceased person could not reasonably be expected to have declined to become a passenger in or on the motor vehicle

Seat belt

Section 49(1)(a) of the Civil Liability Act 1936 similarly creates a presumption of contributory negligence (of 25%) where the plaintiff was not wearing a seat belt.

Again, an exception to that presumption exists pursuant to section 49(2) where the plaintiff establishes, on the balance of probabilities, that they could not reasonably be expected to have avoided the risk.

Section 138(2)(c) of the Motor Accidents Compensation Act 1999 (the MACA) similarly provides that a finding of contributory negligence must be made “where the injured person (not being a minor) or the deceased person was, at the time of the motor accident, not wearing a seat belt when required by law to do so”. The MACA does not contain a specific exception to this provision as it does for the issue of intoxication.

In practice, the court would likely exercise its discretion under section 138(3) to reduce any award of damages recoverable by such percentage as the court thinks just and equitable in the circumstances of the case (which may include a reduction of 0%).

Proceedings below

District Court proceedings ran for a total of 62 sitting days before Deputy Chief Justice Tilmouth.

The trial judge found that Ms Chadwick was an unsatisfactory witness and lied profusely but did accept one key aspect of her evidence, namely that she did not know where she was when she stopped to urinate, despite the nearest street lighting being observable 200 metres away and the hotel they had been drinking at being only 500 metres away.

The trial judge declined to apply the presumed 50% reduction referable to Ms Chadwick voluntarily travelling with an intoxicated driver. His Honour found that Ms Chadwick could not reasonably be expected to have avoided the risk of riding with an intoxicated driver, noting that she was a 21 year old pregnant woman with two older men at 2.00am on the outskirts of a remote town, she was unfamiliar with and as such, she had little choice but to enter the vehicle given the precarious situation she found herself in.

On the seatbelt issue, His Honour accepted from the available expert evidence that there were at least two occasions during the otherwise erratic driving of Mr Allen that the plaintiff could have fastened her seat belt. His Honour accordingly, applied the standard reduction of 25% for the plaintiff’s contributory negligence in this respect.

The Supreme Court of South Australia affirmed (by 2:1) the trial judge’s decision in respect of the reduction for intoxication but unanimously found that the trial judge erred in applying the 25% reduction in respect of failure to wear a seatbelt, finding that it was reasonable for Ms Chadwick to have not fastened her seatbelt in the context of Mr Allen’s erratic driving.

High Court decision

The High Court noted that section 47(2)(b) contemplates an objectively reasonable evaluation of the relative risks of riding with an intoxicated driver as against any risks of pursuing an available alternate course of action.

The relevant inputs into that evaluation are those facts, as they may reasonably be perceived, which bear upon a reasonable assessment of the relative risks or alternate courses of action.

They may include objective facts personal to the plaintiff and aspects of the external environment but does not include subjective characteristics which may reduce the plaintiff’s capacity to make a reasonable evaluation of the relative risks.

The High Court noted that the position under the common law is as stated by Justice McHugh in Joslyn v Berryman1, such that a plaintiff’s subjective, mental or emotional state is irrelevant to the reasonable choice expected of him or her.

The High Court found that nothing in the Civil Liability Act 1936 (SA) suggested a statutory purpose to alter the law to make allowance for such subjective considerations.

The High Court noted that the trial judge’s factual finding that Ms Chadwick did not know where she was had not been disturbed on appeal. Once this was accepted, the High Court identified the relevant inputs into the evaluation of a relative risk required by section 47(2)(b) were that the plaintiff was a young woman, that she was pregnant (and therefore there were more serious consequences to any assault), that she was on a dark and unfamiliar country road, an unknown distance from town in the early hours of the morning. The High Court considered that this would reasonably lead to an evaluation of a real risk of harm and that such risk was greater than the risk associated with travelling in a vehicle with an intoxicated driver, particularly in the early hours of the morning when one would expect to find less traffic on the road.

The court excluded from consideration any subjective characteristics which may have reduced Ms Chadwick’s capacity to make a reasonable evaluation of the relative risks such as impetuosity, drunkenness, hysteria, mental illness or personality disorders.

In relation to the seatbelt issue, the High Court noted that it is not a question of whether it was reasonable or understandable to fail to fasten her seat belt but rather whether she was prevented from fastening her seat belt due to Mr Allen’s driving.

The High Court noted that this was answered by the trial judge’s finding of fact that there were at least two occasions the vehicle was driving on a straight road where she could have fastened her seat belt.

As such, the High Court confirmed the original finding of the trial judge that there would be no reduction on account of the alcohol issue but a 25% reduction on account of the seat belt issue.


The High Court’s decision was reliant in some part on the particular provisions of the South Australian legislation but does have some broader application in confirming the common law’s approach to the assessment of contributory negligence on the objective standard of a reasonable person.

The High Court’s exclusion of subjective features such as impetuosity, drunkenness, hysteria, mental illness or personality disorders creates some tension with a number of lower court decisions in which the evaluation of the standard expected of a reasonable person suffering from an intellectual disability permitted this attribute to be taken into account when assessing contributory negligence.2

The High Court did not engage with any of these lower court cases, presumably because the issue of intellectual disability did not arise in the circumstances of this case. We would urge insurers to remain aware of the potential for further development of this line of authority by plaintiffs seeking to reduce the apportionment of contributory negligence on account of some such impairment, despite the High Court’s comments in this case and the prevailing view following the decision in Joslyn v Berryman.

1[2003] HCA 34
2Leigh Ann Russell bhnf Julie Ann Russell v Rail Infrastructure Corporation [2007] NSWSC 402; Town of Port Hedland v Hodder bhnf Hodder (No 2) [2012] WASCA 212; Goldsmith bht the NSW Trustee and Guardian v Bisset (No 3)[2015] NSWSC 634.


Joe Mancuso

Joe advises insurers on large and complex claims under compulsory third party and statutory insurance classes.

Carl Newton

Carl is an experienced statutory insurance lawyer who helps insurers resolve CTP and major claims.

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