whole or in part from the evidence. Had he taken that route, he
would have received submissions from counsel in the absence of
the jury and proceeded as he saw fit. Alternately, he could have
asked for submissions from counsel on a mistrial, again in the
absence of the jury, and ruled accordingly. In the event that
he had to interrupt Dr. Bail’s testimony mid-trial, he would
have had to consider carefully how best to minimize the potential prejudicial effect of the interruption from the respondent’s
 The point is that the trial judge was not powerless and
should have taken action. The dangers of admitting expert
evidence suggest a need for a trial judge to exercise prudence in
excluding the testimony of an expert who lacks impartiality
before those dangers manifest.
 I am mindful that counsel for Ms. Bruff-McArthur did not
seek an instruction regarding Dr. Bail’s evidence. The law is
generally that the failure to object to a civil jury charge is fatal
to a request for a retrial on appeal based on misdirection or
non-direction. However, this rule is subject to the exception that
where the misdirection or non-direction resulted in a substantial
wrong or miscarriage of justice, it may warrant a new trial:
Pietkiewicz v. Sault Ste. Marie District Roman Catholic Separate
School Board (2004), 71 O.R. (3d) 803,  O.J. No. 2811
(C.A.), at paras. 22-28; and Briscoe Estate v. Canadian Premiere
Life Insurance Co. (2012), 113 O.R. (3d) 161,  O.J. No.
5732, 2012 ONCA 854, at paras. 70-71. In my view, the admission of Dr. Bail’s testimony resulted in a miscarriage of justice.
 I would go further and state that, given the importance of
a trial judge’s ongoing gatekeeper role, the absence of an objection or the lack of a request for a specific instruction does not
impair a trial judge’s ability to exercise her residual discretion to
exclude evidence whose probative value is outweighed by its
 The respondent submits that even if this court concludes
that Dr. Bail’s testimony should have been excluded, there is no
basis to order a new trial because he was just one of many witnesses and his testimony likely did not have a significant impact
on the jury’s verdict.
 It is impossible to gauge with any certainty the impact of
Dr. Bail’s testimony. The fact that he was one of only two witnesses to testify for the defence suggests that his testimony may
well have been an important factor in the jury’s analysis of the
case. In any event, a focus on the inability to measure the precise prejudice caused by the testimony misses the point entirely,
which is that there has been a miscarriage of justice in this case.