Edit: The case of Regina v OM  NSWCCA 109 illustrates how very serious charges can spin out of a minor incident.
My curiosity was piqued by the Elucubrator’s post on Monday about the ability (or not) of law enforcers to trespass while in the course of their investigations.
The facts in Brown v Spectacular Views Pty Ltd & Anor  VSC 197 raise two related questions to me on this issue (which wasn’t central to Macauley J’s judgment, as it turned out): first, to what extent should an absence of legislative authority be taken as the intent of legislators to limit an officer’s authority; and second, to what extent can a legislative absence of authority be taken up by the operation of the common law? Coco v The Queen dealt exclusively with statutory authority. The common law grants public officials authority not otherwise provided in statute, as Nicholson v Avon  1 VR 212 demonstrates.
I wonder whether an occupier’s attempts to eject public officials engaged in legitimate investigative duties might be considered an attempt to pervert the course of justice. In some circumstances it certainly would. Although hindering the police isn’t itself perverting the course of justice, an act which has a tendency to deflect the police from prosecuting a criminal offence or instituting disciplinary proceedings before a judicial tribunal or from adducing evidence of the true facts is an act which tends to pervert the course of justice and, if done with intent to achieve that result, amounts to an attempt to pervert the course of justice: R v Rogerson (1992) 174 CLR 268, Brennan and Toohey JJ at 283 (Mason CJ in agreement).
Attempting to pervert the course of justice is a common law offence which can be made out by a variety of factual circumstances. It’s applied to the making of false statements to police to throw investigators off the scent, threatening witnesses or jurors, making false allegations and concealing evidence. Interfering with a crime-scene seems to fit in that ballpark, too.
An example of just how adaptable the offence is can be found in the extraordinary case of Ishac v R  NSWCCA 107. The applicant was a NSW Probation and Parole officer who supervised offenders serving Community Service Orders (a sentence of unpaid work in the community for a specified number of hours). He was convicted of being an accessory before the fact to attempts to pervert the course of justice after an investigation by the NSW Independent Commission Against Corruption revealed that he assisted people to falsify their timesheets to make it appear as though they had performed their hours.
The applicant argued that the administration of a sentence of a court was not the course of justice, relying upon Einfeld v The Queen (2008) 71 NSWLR 31 and some remarks from another Probation and Parole service case, Tourni  NSWCCA 317. The argument failed (as it also had in Tourni) because although the administration of the order itself might not be the course of justice, the applicant’s efforts were directed at avoiding the offender from being found in breach of his CSO in an impending court proceeding, which would be the course of justice.
McColl JA [at 49]:
In other words, enforcement proceedings had been commenced to revoke the CSO in the Local Court, [the offender on the CSO’s] conduct was intended to circumvent that process and the applicant advised him as to how to achieve that result. It was not conduct which merely occurred during the administration of [the offender’s] sentence. Rather it was calculated to impair the capacity of the Local Court to consider the application for the revocation of [the offender’s] CSO … [the offender’s] conduct, in my view, fell within the meaning of perverting the course of justice in s 312 of the Crimes Act 1900 as explained in the authorities to which I have referred.
Ishac reaffirms that although legal proceedings don’t have to be on foot at the time of the attempt (as stated in R v Rogerson (1992) 174 CLR 268) the course of justice must relate to an actual or potential judicial proceeding.
The related sentence appeal of Khoury v R  NSWCCA 115 shows the seriousness with which such offences are viewed.
In Victoria, Section 320 of the Crimes Act 1958 provides that this offence is punishable to Level 2 imprisonment, a 25 year maximum term of imprisonment. Unlike perjury, the offence is not included in Schedule 2 of the Criminal Procedure Act 2009 and so cannot be heard summarily.
The offence typically attracts stern punishment. Badgery-Parker J stated in Regina v Taouk (1992) 65 A Crim R 387 at 392 that, in the context of an act intended to pervert the course of justice, the fact that the act did not succeed or even was doomed to failure is, “of far less significance than in the case of sentencing for an attempt to commit a substantive crime and the potential seriousness of the consequences is of much greater weight”. Nettle JA attempted a comprehensive review of recent sentences for the offence in R v Buscema  VSC 206. That useful table reads [at 17],
SENTENCES FOR ATTEMPTING TO PERVERT THE COURSE OF JUSTICE
|DPP (Cth) v Fincham||(2008) 75 ATR 545||6 months’ imprisonment|
|DPP v Aydin and Kirsch|| VSCA 87||2 years’ imprisonment|
|DPP v Josefski|| VSCA 265; (2005) 13 VR 85||15 months’ imprisonment|
|R v Aydin|| VSCA 85 (2005) 11 VR 544||15 months’ imprisonment|
|R v Aydin and Flett|| VSCA 87||2 years’ imprisonment and 2½ years’ imprisonment|
|R v Briggs|| VSCA 234; (2000) 117 A Crim R 114||12 months’ imprisonment|
|R v Carey|| VSCA 319||2 years’ imprisonment|
|R v Coombe|| VSCA 94||4 months’ imprisonment|
|R v Davis|| VSCA 276||18 months’ imprisonment|
|R v Dunmall|| VSCA 22||9 months’ imprisonment|
|R v Galea|| VSCA 115||4 years’ imprisonment|
|R v Johns|| VSCA 63||2 years’ imprisonment (reduced from 2½ years)|
|R v Matheas|| VSCA 221||6 months’ imprisonment|
|R v Redmond & Anor|| VSCA 75||3 months’ imprisonment & 4 months’ imprisonment|
|R v Ripper|| VSCA 40||2 years’ imprisonment|
|R v Rodden|| VSCA 24||18 months’ imprisonment|
|R v Rogers|| VSCA 114||15 months’ imprisonment|
|R v Stevens|| VSCA 81||12 months’ imprisonment|
|R v Walsh|| VSCA 98||3 years’ imprisonment|
|R v Yacoub|| VSCA 203||2 years’ imprisonment|
|R v Zaydan & Ors|| VSCA 245||4 years’ imprisonment|
A reference in this Part to perverting the course of justice is a reference to obstructing, preventing, perverting or defeating the course of justice or the administration of the law.
These synonyms provide some clarification of the type of conduct prohibited. It isn’t necessary for the accused to have high-minded notions of justice in order to be guilty. It’s sufficient to make out the offence if the accused intentionally engaged in the acts which, at law, constitute an attempt to pervert the course of justice: Meissner v The Queen (1995) 184 CLR 132 at 144.