Witnesses take the stand at trials to provide whatever information they have that relate to the offence/lawsuit. They do this to help the judge (or the jury) determine the facts of the case. This information is called testimony. Witness testimony is a common type of evidence used at both civil and criminal trials.
You may be asked in writing by the plaintiff’s lawyer (the Crown in criminal cases) or the defendant’s lawyer to attend court to provide testimony. In most cases, the court may actually send you an official court document: a Summons to Witness. If you receive a summons and repeatedly avoid attending court, the court may issue a warrant for your arrest for you to be brought into court. If you can’t attend court as a witness, make sure to call the court and advise them of this.
When you are asked to take the stand, you are also asked to take an oath to provide the truth only. Lying on the stand is a crime. It’s called perjury and comes with significant jail time.
On the stand, you may provide information about the things you know or have witnessed. Both sides of the trial will ask you questions. You can ask for clarification if you don’t understand a question.
Generally speaking, you can’t provide information on what someone else told you. This is called hearsay and is, in most cases, not admissible in court except in limited situations. The reason why you can’t reproduce what you heard from someone else is because that person is often not in court to verify the truth of it.
In a criminal trial, you have a right not to take the stand. In other words, you have a choice of whether you want to be a witness at your own trial. You have this choice because the Crown may ask you difficult questions on the stand that may damage your case. If you’re unsure of whether to take the stand or not, talk to your lawyer.
Going to court as witness or victim at a criminal trial
Canada Evidence Act