Posted on November 4, 2022 by Anna Sinclair, Stuart Simington and

Court considers common law defences to water pollution charge under the POEO Act

A recent decision by the Land and Environment Court provides a useful example of the common law defences that may be raised against a charge of an environmental offence, as well as a good reminder of how difficult it can be to establish these defences.

In Environment Protection Authority v Sydney Water [2022] NSWLEC 100, Sydney Water was charged with three counts of breaching the Protection of the Environment Operations Act 1997  (‘POEO Act‘) with respect to the operation of its sewage treatment system at Carrawood Reserve (‘Premises‘), including the following two charges of water pollution under s 120(1) of the POEO Act:

  • the ‘rising main charge‘ alleged that Sydney Water caused pollutant to be placed into the rising main at the Premises, Carrawood Reserve and Prospect Creek, and
  • the ‘pumping station charge‘ alleged that Sydney Water caused pollutant to flow into the wet well within the pumping station, which then overflowed into Prospect Creek.

Sydney Water successfully raised the common law defence of ‘honest and reasonable mistake of fact’ in relation to the rising main charge. However, it was not successful in arguing the common law defence of ‘necessity’ in respect of the pumping station charge.

Defence of ‘honest and reasonable mistake of fact’

For a strict liability offence, it is not necessary for the prosecution to prove intent to commit the offence (that is mens rea), but the prosecution can come under an obligation to disprove the defence of honest and reasonable mistake of fact.

Justice Moore found that to successfully establish the defence of honest and reasonable mistake of fact, a number of elements must be present, including the following:

  1. there is a positive belief in a state of facts which, if they existed, would make the act innocent and take the act outside the operation of the statute;
  2. the act must be based on a reasonable belief;
  3. the mistake must not be one of law;
  4. a mixed mistake of fact and law will generally be a mistake of law;
  5. the defendant has the evidentiary burden of raising the defence;
  6. the prosecutor must then negative the defence beyond reasonable doubt;
  7. a lack of knowledge or mere ignorance is insufficient to establish the defence; and
  8. the mistaken belief must be sufficiently specific to relate to elements of the offence in question.

Applying these elements to the facts, his Honour concluded that Sydney Water had successfully raised the defence, including because Sydney Water honestly held a positive belief that the rising main was fit for purpose and would remain so until at least 2025 .

The belief was founded on an expert opinion. Sydney Water’s failure to not replace the rising main as part of its scheduled maintenance program prior to the incident was based on its reliance on this belief.

This mistaken belief was not a mistake of law or based on a mixture of fact and law, nor was it based on a lack of knowledge or mere ignorance. Further, Sydney Water was positively aware of, and was responding to, its legal obligations concerning maintenance of rising mains in order to prevent effluent spills.

The EPA failed to negative this defence beyond a reasonable doubt.

This demonstrates the high burden that a defendant has to meet in order to establish the defence.

A defendant would be unlikely to raise this defence where an incident is caused by a malfunction to plant and equipment where there is no evidence to suggest that:

  • the plant was fit for purpose, and
  • was being properly maintained.

Defence of ‘necessity’

In respect of the pumping station charge, Sydney Water sought to defend the charge on the basis that shutting down the pumping station was necessary to enable repair to the rising main, and that the necessity arose because the shutting down was required to prevent an unacceptable risk of harm to human health or life if the main was not able to be repaired as quickly as possible.

Moore J found that the defence of necessity only exists where the circumstances are such as to overwhelmingly impel disobedience to the law, and should not be extended to excuse criminal conduct undertaken otherwise than in response to an imminent threat of death or serious injury.

Further, and following R v Loughnan [1981] VR 443, the following 3 factors had to be established to successfully raise the defence:

  1. there must be a belief on reasonable grounds of the need to avoid immediate and irreparable harm to human health or life in the circumstances where the defendant believed it had a responsibility to prevent that harm from occurring;
  2. the risk of such harm must be one which arises with urgency or immediacy; and
  3. the unlawful act committed in order to prevent the harm must be appropriately proportionate to the harm avoided by its commission.

Moore J found that the first requirement had not been satisfied, primarily for the following reasons:

  • there was no evidence to establish that Sydney Water’s employees expressed any opinion supporting the proposition that a reason, let alone the dominant or sole reason, for shutting the pumping station down, in circumstances where an overflow to Prospect Creek would be the necessary consequence, was to avoid immediate and irreparable harm to human health or life, and
  • the relevant consideration was not an objective one as there must be an identified belief held by an individual, which was attributable to the defendant pursuant to s 169C of the POEO Act, where that belief was held in a fashion satisfying that first of the above criteria.

On this basis, Moore J held that the defence of necessity was not available to Sydney Water, and it was found guilty of the water pollution charge.

In summary, the defence of necessity will only be available in very limited circumstances where the individual/s involved in the incident actually holds a belief that they must take the unlawful action to avoid immediate and irreparable harm to human health or life, and that the response is proportionate to the harm avoided.

The judgment can be read here: Environment Protection Authority v Sydney Water [2022] NSWLEC 100.

If you wish to discuss the issues raised in this article, please contact Anna Sinclair, Ming Gu or Stuart Simington.