The criminal law of Australia is generally administered by individual jurisdictions in the Commonwealth of Australia. These jurisdictions include the six states, the Commonwealth, and the self-governing territories. It is in large part a matter for the states, with only a small subset of criminal activities reserved for Commonwealth government to prosecute.
Australian criminal law was originally received from the English common law, which continued to evolve in Australian courts. Although all states also have some legislation on the criminal law, in some states criminal law has been codified whereas in other the bulk of the law is based on the common law. These may be referred to as ‘common law jurisdictions’ and ‘code jurisdictions’.
New South Wales, South Australia and Victoria are common law jurisdictions. These States have Crimes Acts which list the most common offences and fix their penalties, but do not always exhaustively define the elements of the offence eg Crimes Act 1900 (NSW). It is settled law in the common law jurisdictions that only Parliaments, not the courts, can create new offences.
The “code jurisdictions” are the Commonwealth, the Australian Capital Territory, the Northern Territory, Queensland, Tasmania, and Western Australia. In these jurisdictions a statutory code has been introduced to be a comprehensive statement of criminal law, and are interpreted to replace the common law except in cases of ambiguity. Codification in some cases involved a simple enactment of the common law into a statutory instrument. In other cases the changes were greater as the code was based on legislative instruments from other jurisdictions.
Legislation (including the criminal codes) is further refined by the method of judicial precedent and interpretation.
In addition to explicitly titled criminal code legislation there exists in most jurisdictions a further body of legislative or case precedent, the breach of whose conditions may result in criminal proceedings. eg Summary Offences Act 1966 (Vic)
There are currently plans within some states of Australia to reform the criminal law to achieve greater consistency between states, through the Model Criminal Code. At present, New South Wales, Western Australia and the Northern Territory have participated in the law reform, but the remaining states and territories have not yet agreed to participate.
The Commonwealth has its own criminal jurisdiction for offences against federal laws, however, its jurisdiction in criminal matters is more limited than that of the States. Because the Commonwealth is in transition from the common law model to the code model, some Commonwealth offences are located in the Crimes Act 1914 (Cth) and others are in the code enacted by the Criminal Code Act 1995 (Cth), which abolished all common law offences. The Crimes Act will eventually be repealed when the code expands to cover all offences.
In recent decades, the Commonwealth has increasingly encroached on the powers of the states in relation to criminal law. For instance, the Human Rights (Sexual Conduct) Act of 1994 overrode the sodomy laws contained in the criminal code of Tasmania, the first time a Commonwealth law was expressly used to counteract state legislation. In 1996 the Port Arthur massacre led to the introduction of Commonwealth legislation on gun control, and in 2001 jurisdiction over offences relating to corporations was transferred from the states to the Commonwealth.
Criminal offences under New South Wales law are based on the common law and some statutory provisions in the Crimes Act 1900 (NSW).
Most crimes in Victorian jurisdiction are codified in the Crimes Act 1958 (Vic.). There are also a number of common law provisions for criminal conduct within Victoria.
The Criminal Code Act 1899 (Qld)  is the primary instrument for the source of criminal law in Queensland. The Criminal Code Act was largely the product of Sir Samuel Walker Griffith, then Chief Justice of the Supreme Court of Queensland (and formerly Premier).
The Griffith Code borrowed large elements of the Italian Penal Code 1889 (also known as the Zanardelli Code after its primary supporter) which Griffith described as "in many respects the most complete and perfect Penal Code in existence" and which was translated from Italian by Griffith himself. Griffith also took inspiration from the New York Penal Code 1881. The Griffith Code was later adopted, with some changes, in other parts of the Commonwealth of Nations including Nigeria, Papua New Guinea and Nauru.
The Criminal Code of Queensland has naturally been the subject of further legislative revision and also judicial interpretation and precedent. A generally regarded reference for accurate annotated information on the body of case law associated with the Queensland Criminal Code is Carter's Criminal Law of Queensland which is often used by legal scholars and practitioners more heavily than the Code itself.
One key feature of the Criminal Code is the formal absence of the common law element of mens rea. The Criminal Code provides expressly that a mental element of an offence will be expressly provided for in the provision creating the offence. The practical effect of this stipulation is however not great, as most offences create a mental element of some sort, including recklessness or malice or intent. It should be noted however that the common law concept of actus reus is not excluded by the Criminal Code.
Most crimes in South Australia are codified in the Criminal Law Consolidation Act 1935 (SA). There are also a number of common law provisions for criminal conduct in South Australia.
Tasmania's serious criminal offences, like those in Queensland and Western Australia, are set in a single piece of legislation, the Criminal Code Act 1924. This includes serious offences against the person (murder, manslaughter, death by dangerous driving, wounding, rape, sexual assault), against property (computer crimes, stealing, burglary, robbery and the like) and against society (bribery of public officials, treason, etc.).
Like the Queensland and Western Australian legislation, the mental element (or mens rea) is located under section 13 of the Code, requiring that an act or omission be "voluntary and intentional" for a crime to have occurred. The intent of this is to rule out circumstances where a person is not in control of their own actions - for instance, automatism, insanity, and for some offences, intoxication.
There are numerous other laws where criminal offences may be found. These include the Firearms Act (offences relating to ownership or use of firearms or ammunition), the Police Offences Act (less serious criminal acts and breaches of the peace), the Road Safety (Alcohol and Drugs) Act for drink driving, amongst many others.
Western Australia has an almost exhaustive codification of criminal law in a Criminal Code substantially based on the Queensland one.
The Northern Territory has also an almost exhaustive codification of criminal Law in a similar Criminal Code to that of Queensland and Western Australia. In fact, the drafting of the NT Criminal Code Act 1983, reflected aspects of both the QLD and WA Criminal Codes.