criminal-law evidence rules-of-court self-incrimination
If a court witness self-implicates are they automatically charged?
<p>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.</p>

<p>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?</p>

<p>I am particularly interested in Australian courts.</p>

<p>In the US, they would <em>not</em> 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. </p>

<p>It's <a href="http://www.judcom.nsw.gov.au/publications/benchbks/criminal/privilege_against_self-incrimination.html" rel="nofollow">complicated</a>.</p>

<p>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. </p>

<p>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.</p>

<p>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."</p>

<p>So, now that you know your rights you can:</p>

<ul>
<li>Choose to answer without objection</li>
<li>Object, in which case the judge will decide if you have reasonable grounds

<ul>
<li>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?</li>
<li>If the judge decides you do have reasonable grounds, and the offence is under NSW, ACT or Commonwealth law (only):

<ul>
<li>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.</li>
<li>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.</li>
</ul></li>
<li>If the judge decides you do have reasonable grounds, and the offence is under a jurisdiction other than NSW, ACT or Commonwealth law:

<ul>
<li>you may choose to answer and, if you do, the testimony can be used against you</li>
</ul></li>
</ul></li>
</ul>

<p>No. In the common law world, conviction of a criminal offence can only occur after a judicial process which starts with a charge laid by the prosecution. The decision to lay a charge is never automatic and involves the exercise of <a href="https://en.wikipedia.org/wiki/Prosecutorial_discretion" rel="nofollow noreferrer">prosecutorial discretion</a>.</p>
<p>The other answers have explained the privilege against <a href="https://en.wikipedia.org/wiki/Self-incrimination" rel="nofollow noreferrer">self-incrimination</a>. While this is an important privilege, it is not uncommon for witnesses to waive it and give incriminating evidence. For example, an accomplice may give evidence against a co-accused in the hope of receiving a lighter sentence, even if that evidence is not important enough for the authorities to induce it with an <a href="https://en.wikipedia.org/wiki/Legal_immunity" rel="nofollow noreferrer">immunity from prosecution</a>. Or a defendant facing serious charges might explain apparently inculpatory evidence by admitting responsibility for a less serious offence which has not been charged and is not available as an <a href="https://en.wikipedia.org/wiki/Lesser_included_offense" rel="nofollow noreferrer">alternative verdict</a>. As suggested in the question, the admission might also be incidental and not understood by the witness to be incriminating.</p>
<p>If the authorities choose to prosecute the witness, what the witness said in the previous court proceedings is an <a href="https://en.wikipedia.org/wiki/Declaration_against_interest" rel="nofollow noreferrer">admission against interest</a>. It is admissible in the same way as a voluntary confession outside the courtroom. Although the fact that it was made on oath may mean that it carries more weight, it is not conclusive. The witness might choose to give different evidence in their defence – “I was lying then, but I’m telling the truth now.”</p>
<p>The exercise of prosecutorial discretion depends on the overall strength of the case against the witness, including the evidence of their previous admission. It would also depend on the seriousness of the admitted offence and any applicable statute of limitations. A less serious or historical offence is unlikely to be of interest to the parties in court and may never come to the attention of the prosecuting authorities. More serious offences are likely to be referred to the police for further investigation and prosecution.</p>

<p>Not sure about Australia, but protection against this is a constitutional right under the <em>Canadian Charter of Rights and Freedoms</em>. Most notably, §13:</p>
<blockquote>
<p>Self-crimination</p>
<ol start="13">
<li>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.</li>
</ol>
</blockquote>
<p>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.</p>
