In NSW, Part 3.10 Div 2 of the Evidence Act 1995 grants a privilege against self-incrimination on the ground that the evidence may tend to prove that the witness has committed an offence against, or arising under, an Australian law or a law of a foreign country, or is liable to a civil penalty.
Note that the privilege does not apply to protect you against civil claims by a third-party: you can't claim the privilege to protect yourself from being sued; it only serves to protect you from criminal charges or civil penalties by the state.
Where it appears to the court that a question may lead to self-incrimination the judge should recuse the jury and advise you of your rights. If they don't do this then the testimony is inadmissible, however, if the court couldn't foresee the incrimination the testimony is admissible e.g. Q: "Where were you on August 12, 2014?" A: "I was murdering my wife."
So, now that you know your rights you can:
- Choose to answer without objection
- Object, in which case the judge will decide if you have reasonable grounds
- If the judge decides you don't not have reasonable grounds, you have to answer the question; the testimony can be used against you. Obviously, if you can't show reasonable grounds then it can't be too incriminating, can it?
- If the judge decides you do have reasonable grounds, and the offence is under NSW, ACT or Commonwealth law (only):
- you can choose to answer it willingly and you will get a certificate which protects you from that testimony or any evidence directly or indirectly arising from it.
- if the judge believes it is in the interests of justice that you answer, you can be forced to and you get the same certificate but if your evidence is false they will throw the book at you.
- If the judge decides you do have reasonable grounds, and the offence is under a jurisdiction other than NSW, ACT or Commonwealth law:
- you may choose to answer and, if you do, the testimony can be used against you