Curtailing cross examination on credibility only rarely

R. v. R.D., 2013 ONCA 343 holds:

[33]       Second, although a trial judge has a responsibility to protect a witness from harassing, repetitive or irrelevant cross-examination, defence counsel's cross-examination of the complainant was none of these things.  The question itself that the trial judge stopped the complainant from answering – "and here in court I gave you another opportunity to tell the truth, and instead you lied again" – was an entirely proper question.  It seems to me a trial judge should be very cautious about limiting cross-examination that goes directly to a witness' credibility.