Westerhof also instructs that the opinion given by a participant expert must be based on the witness’ observation of or participation in the events at issue. Here, Dr. Smith testified as to the
problems typical of survivors of childhood sexual abuse — evidence
going to the issue of whether the assaults occurred. His evidence
about survivors as a group was not based on his observation of, or
treatment of, Mr. Imeson, and thus went beyond the proper scope
of any opinion he could provide as a participant expert.
 I conclude that, despite the trial judge’s recognition that
the role of a participant expert is restricted, she permitted Dr.
Smith to exceed his proper role by allowing him to testify about
anything contained in his reports, and in admitting the reports
into evidence, without first carefully examining what opinions
were included in the reports, and the purpose for which it was
proposed that the jury consider such opinions.
 In light of my disposition of this first issue, strictly speaking there is no need to consider the trial judge’s admissibility
analysis under Mohan as it relates to Dr. Smith’s opinion evidence going to the issues of liability and causation. However,
given that I would send this matter back for a retrial, it may be
helpful to discuss the appellant’s Mohan/White Burgess arguments as they relate to that evidence. I note that Westerhof, at
para. 63, recognizes that the court may permit a treating clinician
who complies with rule 53.03 to provide evidence extending
beyond the bounds permitted for opinion evidence of a participant expert, subject to the court’s exercise of its gatekeeping role.
 There is also the matter of Dr. Smith’s evidence about
Mr. Imeson’s mental condition, the treatment that he provided,
Mr. Imeson’s response to treatment and recommended future
treatment. As I have said, I accept that it was appropriate for
Dr. Smith to provide evidence on those points in his capacity as
a participant expert. On appeal, the appellant did not take serious
issue with the admission of that evidence, although he suggested
it may have been unnecessary. As I would send this matter back
for a re-trial, I prefer to leave the question of the admissibility of
that evidence under Mohan/White Burgess for the trial judge on
the re-trial, if the respondent seeks to have Dr. Smith’s evidence
admitted on that point.
(2) The Mohan/White Burgess framework
 The appellant says that Dr. Smith’s evidence failed to meet
the threshold requirements to be admissible under Mohan. In
particular, the appellant argues that Dr. Smith’s expert evidence