The prosecution always has to prove, beyond reasonable doubt, that you have committed the offence charged. If there are a number of elements to an offence, then each of these elements must be proved. In most cases, you will be trying to show that the prosecution has failed to prove its case to the required standard (“beyond reasonable doubt”).
But even if the prosecution can prove its case, there are usually "defences" open to you. If you can establish one of these defences, then you will be found not guilty. The burden of establishing a defence is on you; you must prove the defence "on the balance of probabilities".
Defences to charges are often written into the particular legislation creating the offence, such as the Victorian and Commonwealth Crimes Acts. These are called statutory defences. However, there are also some "common law defences" (based on decisions by judges in previous cases) which can apply to many charges. For instance, "self-defence" and "necessity" might be defences not only to the various charges of assault, but also to protest-related charges.
For instance, you might feel that your life and safety, or social well-being, are fundamentally threatened by a particular corporate or political decision. Your actions may have been motivated by a sense of necessity or self-defence.
Defences such as necessity and self-defence can be very hard to establish successfully. Even if a conservative magistrate might not accept your argument, the fact that you raise the formal defence gives you an entitlement to be heard on your matters of concern. As a compromise, the magistrate might well take your defence into account as "mitigation" (reducing your culpability for the "wrongfulness" of the offence), when she or he sentences you!).
The major common law defences that might be used in a variety of charges (unless excluded by statute) include:
- Claim of right
For instance, you can legally defend yourself against actual or threatened violence so long as you don't use excessive force: you can't shoot someone who threatens to evict you, as this would be an excessive response to the threat. On the defence of necessity, magistrates generally decide that threats to the survival of humankind by nuclear war and environmental damage are not a "great and imminent danger"; but you can still run the defence and explain your actions.
Honest and reasonable belief
On the defence of "honest and reasonable belief", you may be able to state that you believed you had a reasonable excuse for being on a certain prohibited area, for instance, in relation to a charge of trespass. For example, you may state, if it is true, that you had received an invitation and permission from the traditional Aboriginal owners of the area to be on that particular land.
Some charges need authorization
Most charges can be brought by anyone. However, charges involving offences against the police can generally only be brought by police.
There are many Commonwealth charges that require permission from a particular official before they can be brought. For example, offences against the Public Order (Protection of Persons and Property) Act 1971 (Cth) may only be instituted with the consent in writing of the Commonwealth DPP or those authorised by him/her (section 23).
This does not prevent the arrest or charging of these offences, but it is a necessary proof for the completion of the prosecution. In the case of Gulf War protests on Defence Department land the charges were dropped when the Commonwealth Department of Public Prosecutions, following representations, declined to give the necessary consent.
Whilst most State laws apply to Commonwealth places (see Commonwealth Places (Application of Laws) Act 1970 (Cth )) specific Commonwealth provisions often displace State laws altogether.
For example, section 25 of the Public Order (Protection of Persons and Property) Act 1971(Cth) excludes the common law in relation to unlawful assembly, rout and riot from all Commonwealth places. It also excludes the operation of the Unlawful Assemblies and Processions Act 1958 (Vic) and State laws of riot.