I understand your point of you, but clearly if the judge before me understands my mother tongue—even if I come from New Brunswick my mother tongue is French—then regardless of the speed at which I'm speaking, they will have no problem in understanding me. It's the translation that may suffer some distortion or delay.
You say that a lawyer can be asked to speak more slowly but I would just point out that this is also a way to exercise one's rights. They say what they want to say and it comes from the heart. Lawyers are there to ensure that their client, who is a Canadian citizen, gets full justice. This is the final court in the land. I understand that lawyers can be asked to slow down, but this is their way of expressing themselves.
If judges understand both French and English does that not allow lawyers then to express themselves at the speed they wish to? If this is how they exercise the rights of their clients then at least they can do so fully. When citizens hear the ruling, whether it is in their favour or not, at least they will know that they were fully understood. At least they will be able to tell themselves that the proceedings were held in their language and that nobody will have been able to say that they didn't understand what was said fully.