James C. McRuer was an Ontario judge, and one of the first judges to rule on the admissibility of the espionage commission’s evidence. In R v. Mazerall, McRuer rejected a motion to have the commission’s ruled inadmissible. He concluded that witnesses who spoke before a royal commission must specifically demand protection under the Canada Evidence Act if they wished to avoid self-incrimination. He argued that the purpose of the statute was to ensure that statements made before a government tribunal or court were truthful; if witnesses failed to request protection, their testimony could be taken as voluntary and true. Ignorance of the law, McRuer pointed out, was not a defence. The Ontario Court of Appeal upheld his decision and concluded that truthfulness was a matter for the jury to decide. This decision was then cited by judges who reached similar conclusions in the trials of Gordon Lunan, Raymond Boyer, and Durnford Smith. In R v. Mazerall, McRuer concluded that he was “not at all clear that this court has, in these proceedings, any jurisdiction to review the conduct of the commission or to decide that a commission acting with apparent lawful jurisdiction has at any time by its conduct deprived itself of jurisdiction.”

Curiously, McRuer would later become an important figure in the civil liberties movement (he would also be appointed chief justice of the Ontario High Court). Among his most prominent achievements was chairing Ontario’s 1963 Royal Commission on Civil Rights, which led to the most significant overhaul of statutes in Ontario’s history (reforms to better protect individual rights in provincial law). The McRuer Commission recommended that a bill of rights be created for Ontario and that the Public Inquiries Act be amended to ensure that witnesses had access to legal counsel when speaking before a government inquiry.