Undoubted authority of a trial judge to control the proceedings, including the authority to require that witnesses are fairly questioned, and not subject to unfocused, repetitive, ambiguous or irrelevant questions

R. v. Windibank, 2012 ONCA 237 has useful language on the authority of the Court to control questioning of witnesses:

[16]       The appellant acknowledges the undoubted authority of a trial judge to control the proceedings, including the authority to require that witnesses are fairly questioned, and not subject to unfocused, repetitive, ambiguous or irrelevant questions.  In our view, the interventions in this case did not extend beyond the permissible, impede the appellant's right to make full answer and defence, or give rise to a reasonable apprehension of bias.