If a witness under oath in court gives evidence that reveals they have committed a previously unknown crime or offence, are they automatically charged or is there another process that may or may not be followed before they are charged? They don't have an explicit immunity agreement, they have just revealed evidence that implicates them. The crime or offence doesn't have to be the one before the court.

An example from TV: A man is asked how he was in a position to witness the assault. He says, "I was in my garden at the time ritually slaughtering a goat." He comes from a country where ritually slaughtering goats is done by civilised people and he genuinely doesn't realise that it's illegal in this country. Nobody could anticipate that he would say that in advance and warn him not to. Would he be automatically charged or would it be discretionary?

I am particularly interested in Australian courts.


It's complicated.

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
  • I was more thinking of a scenario where a witness unwittingly incriminates themself, rather than them being aware that they could potentially do so if they're not careful.
    – CJ Dennis
    Feb 3 '16 at 10:24
  • It's the court's job to inform them they could incriminate themselves
    – Dale M
    Feb 3 '16 at 20:15
  • What about when it's unforeseen? I think I need to edit my question to make it lawyer-proof!
    – CJ Dennis
    Feb 4 '16 at 5:41

In the US, they would not be automatically prosecuted. The prosecutor would have to find out about the testimony, decide to prosecute, and go through all the normal processes they otherwise would, but they have an additional piece of evidence. Per the 5th Amendment to the US Constitution, a witness cannot be forced to answer a question that would incriminate them. If the question was objected to on this ground and the objection overruled, the witness' answer would not be admissible against that witness at trial, and the prosecutor would have to prove the case using other evidence.

  • Does that also mean the police wouldn't be allowed to investigate based on that information?
    – gnasher729
    Feb 4 '16 at 20:01
  • To the best of my understanding, the police could investigate based on the information, if they find out about it and care enough that they choose to do so.
    – WBT
    Feb 4 '16 at 20:39

Not sure about Australia, but protection against this is a constitutional right under the Canadian Charter of Rights and Freedoms. Most notably, §13:


  1. A witness who testifies in any proceedings has the right not to have any incriminating evidence so given used to incriminate that witness in any other proceedings, except in a prosecution for perjury or for the giving of contradictory evidence.

Unless you are charged with perjury, which can be summed up by intentionally lying to a court of law, the Crown can not charge you for a crime that you may give rise to, provided that the testimony is yours. It might raise an eyebrow among police services, but that testimony that you provide in someone else's trial cannot be used against you.

  • Interesting. I have heard a magistrate in an Australian court direct a witness not to answer a particular question because it could be admission of a crime or offence. Something like: "I refuse to answer on the grounds that I might incriminate myself."
    – CJ Dennis
    Feb 3 '16 at 2:51
  • @CJDennis I'll definitely try to find something on that. I don't know in the slightest Australian law, but I wouldn't be surprised - having a right would be kind of important in the administration of justice, imo. Even the U.S. has related provisions in their constitution. Do you think you have an idea of where I could find the example that you list?
    – Zizouz212
    Feb 3 '16 at 2:53
  • This page goes into "Privilege in respect of self-incrimination in other proceedings" but it is very long! I haven't read the whole thing but it seems it's more about the legal privilege than what happens if a witness does incriminate themself.
    – CJ Dennis
    Feb 3 '16 at 3:01
  • @CJDennis Thanks! That should be a good starting point. I'll hopefully try and update my answer by tomorrow if I can find something. It's getting late here and I should try to catch some sleep :)
    – Zizouz212
    Feb 3 '16 at 3:05

Let's say in court "I was just leaving the shop with a bar of chocolate that I hadn't paid for, when I saw the defendant taking his gun and shooting two police officers".

I don't think I would be automatically charged with theft, because it just isn't worth it. And while it might have been theft what I did, proving it might be difficult.

  • 1
    What about the other way around. "I was shooting the two guys when I saw the defendant stealing all the money in the register."
    – mikeazo
    Feb 16 '17 at 3:22

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