What’s the difference between the common law offence of wilful exposure and the statutory offence of obscene exposure?
The location where the offence might occur is the main difference.
Statutory obscene exposure must occur in or within view of a public place.
Common law wilful exposure can occur anywhere, provided that the exposure was seen by one person and could have been seen by another. (Wilful exposure is in fact a specific species of public nuisance comprising offences outraging public decency. The two-person rule is the ‘public’ element of the offence.)
Amendments to s 53 of the Magistrates’ Court Act1989 back in 2006 allow the Magistrates’ Court to hear and determine certain common law indictable charges. Common law offences that attract Level 5 and 6 punishment became triable summarily. Those punishment levels for common law offences are prescribed by s 320 of the Crimes Act 1958:
- Breach of prison
- Bribery of public official
- Common assault
- Criminal defamation
- False imprisonment
- Misconduct in public office
- Public nuisance
- Unlawful assembly
- Wilful exposure
Edit: Now, Criminal Procedure Act 2009 s 28 provides that common law offences punishable by Level 5 or 6 imprisonment may be determined summarily.
These changes have led to more statutory and common law charges being dealt with together in the Magistrates’ Court. Where once the police informant chose between process in the County Court for common law offences or the Magistrates’ Court for similar summary offences, the summary jurisdiction may now hear both. (Provided the Court deems it appropriate and the accused consents to the jurisdiction for the common law charges.)
There’s no impediment to alleging multiple offences that refer to one alleged act or transaction by the accused: s 51 Interpretation of Legislation Act 1984 . Failure to do so might lead to duplicity: see, for example, R v His Honour Judge Hassett (1994) 76 A Crim R 19.
Some common law offences are so similar to their statutory cousins that there’s little or no forensic advantage if the prosecution proceeds with both types of charge. (Except common law offences have no limitation period for commencing criminal process, because they’re all indictable.) Common assault is an example of offences that are almost the same in common law and statutory form. (See R v Patton, Caldwell and Robinson  1 VR 7, discussing common assault as it applies to an offence of burglary.)
Other times the elements of the offences are quite different. An example of this is wilful exposure contrary to common law. It was added to the list in Crimes Act s 320 recently by s 13 of the Criminal Procedure Legislation Amendment Act 2008.
In contrast, obscene exposure is a statutory offence found at s 19 of the Summary Offences Act 1966. It hasn’t always been there, but was inserted when the Vagrancy Act was repealed in 2005. The re-enacted offence reads:
A person must not wilfully and obscenely expose the genital area of his or her body in, or within the view of, a public place.
Penalty: 2 years imprisonment.
Common law exposure doesn’t require the prosecution to prove the act took place in or within the view of a public place: R v Fonyodi  VR 86. It is sufficient that one person did, in fact, see the act, and that another person of any age was in a position to see it, without the requirement for the observer or potential observers to be in a public place: R v Towe  VLR 381;  ALR 502.