Can a judge be compelled to testify regarding their deliberative deliberations?

Deliberative secrecy privilege of is well established: a judge cannot be compelled to testify regarding his or her decision-making process. The courts have granted similar protection to members of administrative tribunals. Even if deliberative secrecy is not the same for administrative tribunals as for courts of law, secrecy remains the rule and can be lifted only when the party wishing to do so can present valid reasons for believing that the process followed did not comply with the rules of natural justice. Tremblay v. Quebec (Commission des affaires sociales), 1992 CanLII 1135 (SCC), [1992] 1 S.C.R. 952, p. 965.