Règle correspondante
Practice Relating to Rule 100. Fair Trial Guarantees
Section H. Assistance of an interpreter
Canada’s LOAC Manual (1999) provides that accused persons in occupied territory must “be aided by an interpreter, both during preliminary investigation and during the hearing in court”. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 12-7, § 58.
Canada’s LOAC Manual (2001) states in its chapter on rights and duties of occupying powers:
Unless they voluntarily waive such assistance, accused persons must be aided by an interpreter, both during preliminary investigation and during the hearing in court. They have the right at any time to object to the interpreter and to ask for a replacement. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 1232.4.
In 2013, in the Mungwarere case, Canada’s Ontario Superior Court of Justice acquitted Mr. Mungwarere of charges of genocide and crimes against humanity in Rwanda in 1994. The Court stated:
12. The accused chose for the trial to be held in French. His mother tongue is Kinyarwanda, the official language of Rwanda. Nevertheless, he perfectly understands and speaks French, as many of his fellow countrymen who have completed their secondary education. The accused subsequently accepted for the trial to be held bilingually in order to allow for some parts of it to take place in English. This change was largely needed to allow one of his attorneys, which preferred the use of the English language while pleading, to do it in English. Throughout the proceeding, all use of English was simultaneously translated to French by certified translators.
13. On the other hand, the vast majority of testimonies were given in Kinyarwanda. This required the hiring of interpreters who could translate and communicate the questions to the witnesses in Kinyarwanda and translate their answers to French …
15. All parties soon realized that it was hard to translate in a satisfactory way from Kinyarwanda to French and from French to Kinyarwanda. Soon after the beginning of the trial, I put in place a system of verification which was approved by all parties. If the accused, the interpreter chosen by the Crown or even one of the official interpreters had a doubt on the validity of the interpretation given by the official interpreter in office at the time, he had to communicate it immediately to the court. The testimony would have been suspended at that moment and a consultation would have followed between the different interpreters and the accused until everybody would have agreed on the right interpretation. This system worked very well. As the trial went on, such interventions became less frequent, surely because the interpreters became more and more familiar with the particular expressions used by the witnesses. 
Canada, Ontario Superior Court of Justice, Mungwarere case, Reasons for Judgment, 5 July 2013, §§ 12–13 and 15.
In 2004, in its fifth periodic report to the Human Rights Committee, Canada reported:
In R. v. Beaulac, the Supreme Court set out a new principle of interpretation of language rights … The Court noted the positive nature of language rights, establishing a link with the notion favoured in the area of international law that the freedom to choose is meaningless in the absence of a duty of the State to take positive steps to implement language guarantees. In the same case, the Supreme Court of Canada ruled that the language-of-trial provisions of the Criminal Code (the right of any accused to have a trial before a judge, a jury and a prosecutor who speak the official language (English or French) of the accused, the right of the accused to have a judgment written in his official language, and the right of the accused, witnesses and the accused’s counsel to be assisted by an interpreter) create an absolute right, provided a request is made within the time allowed. The Court confirmed that such language rights are completely distinct from trial fairness and, as such, are not contingent upon the ability of the person making the request for interpretation services to understand the proceedings in the other official language. 
Canada, Fifth periodic report to the Human Rights Committee, UN Doc. CCPR/C/CAN/2004/5, 18 November 2004, § 177.