At common law a court may review, correct or alter its judgment any time until its orders have been perfected: Achurch v The Queen (2014) 253 CLR 141 at [17]. The power is inherent in superior courts and implied in statutory courts including inferior courts and may be extended by statutory provisions: Achurch v The Queen at [17].

The slip rule allows for a limited correction of an order after its final entry: Achurch v The Queen at [18]. Under Pt 53, Div 1, r 12 District Court Rules 1973, entry of the sentence on the court file, signed by the judge, constitutes a formal record of the sentence: Rickard v R [2007] NSWCCA 332 at [7].

The Court of Criminal Appeal has a power to set aside or vary an order under r 50C Criminal Appeal Rules within 14 days after the order is entered. The power to correct mistakes falling within the “slip rule” exists independently of r 50C. The rule does not limit the operation of the slip rule: R v Green [2011] NSWCCA 71 at [24], [27].

Section 43 Crimes (Sentencing Procedure) Act 1999 makes provision for a court to reopen proceedings to correct sentencing errors either on its own initiative or on the application of a party to the proceedings. It provides:

Section 43 provides a conditional statutory power to correct a penalty beyond the limits of the inherent and implied powers of the courts and the slip rule: Achurch v The Queen (2014) 253 CLR 141 at [19]. It is to be distinguished from the implied or inherent power to correct accidental “slips” or omissions to ensure that orders reflect the intention of the court: R v Green [2011] NSWCCA 71 at [21], [27].

Section 43 applies to criminal proceedings (including proceedings on appeal) in which a court has: (a) imposed a penalty that is contrary to law, or (b) failed to impose a penalty that is required to be imposed by law: s 43(1). Upon reopening the court may impose a penalty that is in accordance with the law, and if necessary, may amend any relevant conviction or order: s 43(2).

The section only applies to criminal proceedings in which one of two conditions [in ss 43(1)(a) and 43(1)(b)] is fulfilled. For the purposes of s 43(1)(b) what must be contrary to law is the “penalty”. Merely by demonstrating that the court has erred in law or fact does not meet the condition in s 43(1)(a).

The High Court in Achurch v The Queen at [32] set out examples of circumstances in which a penalty may be said to be contrary to law:

The section does not extend to a general re-opening of proceedings. It does not permit sentenced offenders to re-litigate what has already been litigated, or seek a different outcome on new or different evidence: Bungie v R [2015] NSWCCA 9 at [40], [41].

The principle of finality — that resolved controversies are not to be reopened except in a few, narrowly defined circumstances — informs the construction of s 43 Crimes (Sentencing Procedure) Act 1999 and the limit of its purpose: Achurch v The Queen (2014) 253 CLR 141 at [16]. The power cannot be applied to any penalty where the court was influenced by an error of law or fact because such an approach does not fit with the text of s 43, or its limited purpose: Achurch v The Queen at [32], [36].

The principle of finality can only be qualified by clear statutory language. The broad construction given by earlier Court of Criminal Appeal decisions (Erceg v The District Court (NSW) (2003) 143 A Crim R 455, Ho v Director of Public Prosecutions (1995) 37 NSWLR 393, Meakin v Director of Public Prosecutions (2011) 216 A Crim R 128 and R v Finnie (No 2) [2004] NSWCCA 150 at [31]–[32]) “leaves the boundaries between correction and appeal porous and protected only by the exercise of the sentencing court’s discretion”: Achurch v The Queen at [36].

Further, in Taylor v R [2013] NSWCCA 157, it was held s 43 can be utilised to remedy the miscalculation of commencement dates or parole periods: [7]. In Achurch v R (No 2) (2013) 84 NSWLR 328, the court said s 43 can be used where the court has made an “error of computation or the like”: [66]. Computation errors or errors in relation to commencement dates (after the High Court decision of Achurch v The Queen) have to be corrected using the courts inherent or implied power or under the slip rule referred to above.

Section 43 cannot be used by first instance courts to review Muldrock v The Queen (2011) 244 CLR 120 appeals because a penalty is not “contrary to law” within the terms of the section only because it is reached by a process of erroneous legal reasoning or factual error: Achurch v The Queen at [37]. Section 43 cannot be used to alter a driving disqualification period after a s 10A order (under the Crimes (Sentencing Procedure) Act) has been imposed: Davis v Director of Public Prosecutions (NSW) [2011] NSWSC 153 at [43].