A criminal trial is an adversarial process. First, a prosecutor, on behalf of the government (i.e., the ‘Crown’) has to call evidence by getting witnesses, victims, officers, and, if applicable, experts to testify. These witnesses may then tell the judge or jury what happened. If there is any material evidence, such as video footage, photographs, or other items, an officer will typically testify to produce that evidence in court for the judge or jury.
After the prosecutor has called all their evidence, you and your defence lawyer have the option of calling evidence by getting your own witnesses to testify. If you are the person charged, you may also testify but you are not required to do so.
Whenever any witness testifies, there will be direct examination, followed by cross-examination, and then followed by re-examination. In direct examination, the person calling the witness (either the prosecutor or your criminal defence lawyer) will ask open-ended questions about the case. In cross-examination, the other lawyer will have an opportunity to ask leading questions (meaning, yes-or-no questions). In re-examination, the first lawyer gets to ask a few follow up questions about anything that arose in cross-examination and wasn’t addressed in direct-examination.