14.13 The Australian Constitution does not expressly require that criminal offences include the element of mens rea, nor has it been implied into the Constitution by the High Court.
Principle of legality
14.14 The principle of legality provides some protection to the principle of mens rea. When interpreting a statute, courts will presume that Parliament did not intend to create a strict liability offence, unless this intention was made unambiguously clear.
14.15 In CTM v The Queen, the High Court considered whether the common law defence of honest and reasonable mistake of fact applies to s 66C(3) of the Crimes Act 1900 (NSW), which makes it an offence for a person to have sexual intercourse with another person between the ages of 10 and 16. The majority of the High Court stated:
While the strength of the consideration may vary according to the subject matter of the legislation, when an offence created by Parliament carries serious penal consequences, the courts look to Parliament to spell out in clear terms any intention to make a person criminally responsible for conduct which is based on an honest and reasonable mistake.
14.16 As demonstrated by the majority decision in CTM v The Queen, this represents a high bar. Amendments to the Crimes Act 1900 (NSW) in 2003 removed the express statutory defence under s 77(2)(c) that the person ‘had reasonable cause to believe, and did in fact believe, that the child was of or above the age of 16 years’.
14.17 These amendments were designed ‘to provide equal treatment of sexual offences against males and females’. A majority of the High Court held that the offence in s 66C is not an absolute liability offence (ie, an offence of honest and reasonable mistake is available), despite the repeal of s 77(2), because it does not preclude the ongoing operation of the common law principle that an honest and reasonable mistake generally precludes criminal liability. The Court stated:
The New South Wales Parliament regarded the ‘express defence’ in s 77(2) as no longer appropriate. It was a defence that, in its terms, differentiated between homosexual and heterosexual activity, so it at least had be to be changed if there were to be the desired equalisation. It could not have been left as it was. Yet the problem to which that provision was addressed did not disappear; and the long-standing and well-understood principle which provided an alternative response to the same problem remained potentially applicable in the absence of ‘the clearest and most indisputable evidence [concerning] the meaning of the Act’.
14.18 Article 14(2) of the International Covenant on Civil and Political Rights (ICCPR), which relates to the presumption of innocence, provides protection to the principle of mens rea. However, international instruments cannot be used to ‘override clear and valid provisions of Australian national law’. However, where a statute is ambiguous, courts will generally favour a construction that accords with Australia’s international obligations.
The principle of statutory interpretation now known as the ‘principle of legality’ is discussed more generally in Ch 1.
He Kaw Teh v R (1985) 157 CLR 523, 528 (Gibbs CJ); Sherras v De Rutzen  1 QB 918.
CTM v The Queen (2008) 236 CLR 440,  (Gleeson CJ, Gummow, Crennan and Kiefel JJ). This finding was supported by the other judges: Ibid ,  (Kirby J),  (Hayne J), –.
New South Wales, Legislative Assembly, Parliamentary Debates (7 May 2003), 376.
New South Wales, Legislative Assembly, Parliamentary Debates (21 May 2003), 900.
CTM v The Queen (2008) 236 CLR 440,  (Gleeson CJ, Gummow, Crennan and Kiefel JJ).
Minister for Immigration v B (2004) 219 CLR 365,  (Kirby J).
Minister for Immigration and Ethnic Affairs v Teoh (1995) 183 CLR 273, 287 (Mason CJ and Deane J). The relevance of international law is discussed more generally in Ch 1.