25/3/2025

Proportionate Liability Legislation:

Civil Liability Act (2002) - Causation

This note should be considered along with our series of notes about proportionate liability legislation in Western Australia. Those notes include Joint & several liability, versus proportionate liability, The Civil Liability Act (2002) – Introducing Proportionate Liability, and The Civil Liability Act (2002) – Contracting out (standard of care).

For more notes on other relevant topics of interest, please see: www.geoffreywakerandassociates.com.au

Introduction

In 2003, the scope of the Civil Liability Act (2002) (CLA) was expanded in a number of ways, partly codifying the law of negligence in Western Australia, including in relation to causation which was introduced in Section 5C in Part 1A of the Act.

Although the intention of parliament was to remove confusion created by the various formulations of the legal tests of causation that had developed in the common law (see the Civil Liability Amendment Bill 2003 Explanatory Memorandum), it seems some confusion remains.

The legal concept of causation

Damage is not actionable in negligence unless it has been caused by the fault of another. In the law, the concept of causation is different to notions of cause and effect in philosophy and science. The law’s function is to ascertain or apportion legal responsibility for a given occurrence,[1] and this process requires an assessment of whether there is a causal connection between an identified negligent act or omission and a given occurrence.[2]

Causation under the CLA

Under section 5C(1) of the CLA, a determination that the fault of a person (the tortfeasor) caused particular harm requires two factors. First, that the fault was ‘a necessary condition of the occurrence of the harm’ (s5C(1)(a)), referred to in the CLA as factual causation. The High Court has recognised this test as a statutory statement of the common law ‘but for’ test of causation.[3] The second factor is a normative assessment by the court that it is appropriate for the scope of the tortfeasor’s liability to extend to the harm so caused (scope of liability) (s5C(1)(b)).

For the purposes of section 5C(1)(a), to establish factual causation a plaintiff must demonstrate that the negligence was ‘a’ necessary condition of the occurrence of harm (‘a’ cause), as opposed to ‘the’ necessary condition (‘the’ cause) of the plaintiff’s damage. In Western Australia, this assessment has come to include a consideration of whether a particular negligent act or omission ‘caused or made a material contribution’ to the harm suffered.[4]

Enter some confusion. The expression ‘material contribution’ is used in a number of different ways in the context of causation in torts.[5]

The alternative use of ‘material contribution’ - section 5C(2)

There are cases where a person’s fault cannot be established as a necessary condition of the harm suffered (so factual causation cannot be established under s 5C(1)(a)) but where nonetheless the fault of a person may be taken to establish factual causation for an action in negligence. The CLA accounts for these cases in section 5C(2) (section 5C(2) has no role to play when factual causation can be established under section 5C(1)(a)).

Section 5C(2) applies in an ‘appropriate case’ in which, in accordance with established principles, fault cannot be established as a necessary condition by reason of the particular circumstances of the case.[6] Such circumstances may be exemplified by the UK case of Bonnington Castings Ltd v Wardlow.[7]

In that case, Mr Wardlow had developed a disease (pneumoconiosis) caused by years of gradual accumulated exposure to silica dust. Part of the exposure to the dust was due to the negligence of the appellant, however, it was impossible to separate out the role of the dust caused by the appellant’s negligence and other exposure Mr Wardlow had to the dust, in determining the cause of the pneumoconiosis. No single part of the accumulated exposure to silica dust could meet a ‘but for’ test of causation so instead, to establish causation, the negligence of the appellant was found by the court to have ‘materially contributed’ to the harm.

This alternative use of the phrase ‘materially contributed’, used when the ‘but for’ test could not be satisfied because of the particular circumstances of the case, may be the cause of some confusion in ascertaining the appropriate test of causation in some cases. In Western Australia, s5C(1)(a) is a statutory restatement of the ‘but for’ test, yet the full court of appeal has said that section 5C(1)(a) may encompass a consideration of whether a negligent act or omission ‘materially contributed’ to the harm caused.[8]

Exactly which case will be an ‘appropriate’ case for the applicability of section 5C(2) of the CLA remains uncertain. However, section 5C(2) will not assist plaintiffs who cannot demonstrate factual causation simply because a particular precaution that was not taken by a defendant might have prevented the harm caused.[9] Something more will be required.

Contracting out of the CLA - Causation

When the scope of the CLA was expanded in 2003, a limited contracting out provision was

included (section 4A) so as not to restrict a person’s right to make express provision for their

rights under contract. Such contracting out requires agreement in writing. Under section 4A, a written agreement signed by the parties to it may contain an express provision by which a provision of Part 1A (or 1B, 1C, 1CA, 1D, 1E or 1F) may be excluded, modified or restricted.

The statutory test for causation in Section 5C is contained in Part 1A, and can therefore be excluded, modified or restricted by written agreement between parties, in accordance with section 4A.

If contracting parties wish to take advantage of the limited contracting out provision, it is for them to define, in say a suitable written contractual indemnity, the nature of any cause which justifies the transfer of risk between them.

Care is required in the drafting and interpreting of such indemnities, as an indemnity will only apply to losses from the cause against which the indemnity is granted. Indemnities may not apply to losses which have a separate, distinct cause. It will also depend on the proper construction of the written agreement whether any claim involving a cause that falls outside the limits of the contractual indemnities will be assessed using the provisions of the CLA or whether those provisions are entirely excluded by the agreement.

[1] March v Stramare [1991] HCA 12; (1991) 171 CLR 606, 509 (Mason CJ)

[2] East Metropolitan Health Service v Ellis (by his next friend Christopher Graham Ellis) [2020] WASCA 147 (Ellis) [255]

[3] Strong v Woolworths [18] although the court was referring to the s 5D(1)(a) of the NSW Act which is identical in its terms.

[4] Ellis (n 2) [597], following the decision in Western Australia v Watson [1990] WAR 248, 286 (Malcolm CJ, Brinsden & Seaman JJ)

[5] Ellis (n 2) [596] citing Strong v Woolworths Ltd [2012] HCA 5; (2012) 246 CLR 182 at [22]

[6] See Ellis (n 2) [605]-[613]

[7] Bonnington Castings Ltd v Wardlow [1956] AC 613

[8] Ellis (n 2) [599]

[9] Ellis (n 2) [611]

For related information in the Series on Proportionate Liability Legislation, see:

‘The Civil Liability Act (2002) – Contracting Out (Proportionate Liability)’.

(Available under ‘Insights’ here: www.geoffreywalkerandassociates.com.au)

Geoffrey Walker & Associates ABN 92 495 396 

Liability Limited by a scheme approved under Professional Standards Legislation