OPINION: In a case starting on Wednesday, the High Court will be asked to determine the meaning of corruption. Well, to be more specific, the High Court will be asked to interpret the meaning of “corrupt conduct” in New South Wales' Independent Commission Against Corruption Act, the act that establishes the state’s ICAC and sets out its functions.

It is an important question for a number of people currently under investigation by ICAC. But it is also a narrow question: it is limited to what amounts to corruption under the NSW statute.

Margaret Cunneen’s allegedly ‘corrupt conduct’

In May 2014, NSW’s high-profile and divisive deputy senior Crown prosecutor Margaret Cunneen, SC, and her son were alleged to have told his girlfriend to fake chest pains after a car accident so as to avoid a police breath test. ICAC received a tip-off and started a public inquiry.

ICAC has the power to conduct a public inquiry “if it is satisfied it is in the public interest to do so”. Cunneen, her son and his girlfriend challenged ICAC’s power to conduct its investigation in the Supreme Court because they claimed that their alleged actions did not amount to “corrupt conduct”. They also wanted ICAC to provide its reasons for deciding to investigate the matter and hold a public inquiry.

Cunneen was initially unsuccessful in the Supreme Court, but a majority of judges in the NSW Court of Appeal (2:1) overturned that decision. ICAC is now seeking to have the High Court finally decide the case.

‘Corrupt conduct’ in the NSW Act

The Independent Commission Against Corruption Act establishes the NSW ICAC and confines its functions. The act gives it power to investigate “corrupt conduct”. ICAC relies on the definition under Section 8(2) to investigate Cunneen. That says corrupt conduct includes:

… any conduct of any person (whether or not a public official) that adversely affects, or that could adversely affect, either directly or indirectly, the exercise of official functions by any public official, any group or body of public officials or any public authority and which could involve any of the following matters.

Twenty-five matters are listed, including bribery, blackmail, fraud and, relevantly for Cunneen, perverting the course of justice.

ICAC argues that the alleged conduct of Cunneen and her son adversely affected the police officer’s exercise of their official functions and amounted to perversion of the course of justice.

The NSW Court of Appeal’s view

Two NSW Court of Appeal judges, Justices Basten and Ward, held that section 8(2) extends only to conduct that could lead a public official to exercise their functions dishonestly, partially or otherwise improperly.

They found that Cunneen’s alleged conduct did not meet this definition. It would not have led the police officer to exercise their powers improperly.

The NSW Chief Justice Bathurst dissented. He held that the alleged conduct did amount to corrupt conduct. It would have limited or prevented the police officer from properly investigating the suspected offence.

In the High Court, ICAC is arguing that the broader meaning adopted by Chief Justice Bathurst is correct.

The legal arguments

Like so many legal problems, the case’s resolution will turn on the interpretation of the specific statute. Judges employ many techniques to determine statutory meaning.

Judges start with the ordinary and “natural” meaning of the words themselves. But the ordinary meaning often involves a degree of ambiguity: words can mean more than one thing. The primary rule for resolving ambiguity is that a meaning consistent with the purpose of the statute should be preferred.

ICAC argues that the Chief Justice’s wider interpretation is correct because it is consistent with the ordinary meaning of the words in section 8(2). ICAC argues that the majority in the Court of Appeal improperly added a “gloss” to the NSW parliament’s language by reading into the definition an additional requirement that the conduct leads a public official to exercise their functions improperly.

ICAC also argues that a broad interpretation of corrupt conduct is consistent with the act’s overarching purpose: that parliament intended to bring a wide range of activities within ICAC’s investigative purview.

However, Cunneen argues that the approach of the majority in the Court of Appeal was consistent with the purpose of the act, and other provisions in the act. Section 2A states that the act is directed at the investigation of corruption involving or affecting public authorities and officials. The narrower interpretation of corrupt conduct is argued to be consistent with this purpose by limiting it to conduct that could lead a public official to act corruptly or improperly.

Further, Cunneen argues that the narrower definition is consistent with another rule of statutory interpretation, known as the “principle of legality”. This rule requires parliament to be “irresistibly clear” when it intends to legislate contrary to fundamental rights and principles.

During an ICAC investigation, many fundamental rights and principles are overridden. These include the right to silence and the privilege against self-incrimination. According to the principle of legality, if parliament wanted to increase ICAC’s investigatory jurisdiction through a broad definition of corrupt conduct, it had to be irresistibly clear in its language. Cunneen argues that it wasn’t.

The potential impact on other ICAC investigations

The High Court has not necessarily decided to hear ICAC’s appeal. It has agreed to hear an application for special leave to appeal on Wednesday, at the same time it hears arguments in the full appeal.

ICAC claims that the High Court should determine the full appeal because of the large consequences attached to the Court of Appeal’s decision, not just in Cunneen’s case. It claims a number of its concluded and ongoing investigations – including its high-profile investigations into Australian Water Holdings, political donations and Eddie Obeid – might be impacted if the narrow interpretation is correct.

The effect of Cunneen’s case on these investigations is not explained in detail and is not immediately clear. At least in its more high-profile investigations, much of the conduct falls squarely in ICAC’s jurisdiction regardless of whether a wide or narrow definition of corrupt conduct is applied.

The impact of the decision on other states and Cunneen

Every Australian state now has some form of a standing anti-corruption commission. Each state has an act setting out that body’s investigative jurisdiction.

The definition of corruption in these acts varies considerably. The statutes in Queensland and Victoria have broadly similar definitions of corrupt conduct to that in NSW. But they are not so similar that the case is likely to have much relevance to the investigative jurisdiction of the Queensland and Victorian bodies.

In both states, the definition makes clear that the conduct must adversely affect the honest or otherwise proper performance of a public official’s functions or powers.

For Cunneen, her son and his girlfriend, if the High Court agrees with the Court of Appeal and takes a narrow view of corrupt conduct, their saga doesn’t necessarily end there. Nothing in this case means that their alleged conduct is not a criminal offence, or that police might not be able to investigate it.

The case will decide a narrow question: can ICAC investigate their conduct?

What should ICAC be investigating?

Regardless of what happens in the High Court, it is open to the NSW parliament to amend the act. Parliament could make it clear that ICAC’s investigatory power extends to conduct that may limit or prevent public officials from the proper exercise of their functions, regardless of whether it would have made them exercise those powers in a corrupt or improper way.

Parliament could also amend the act to clarify that ICAC’s function is to investigate official and serious corrupt conduct only, leaving conduct such as that allegedly engaged in by Cunneen to the police for investigation.

Ultimately, the question of what conduct ICAC should investigate is one for the NSW parliament.

Gabrielle Appleby is an Associate Professor in Law at UNSW.

This opinion piece was first published in The Conversation.