— the opinion to be given is based on the witness's observation of or
participation in the events at issue; and
— the witness formed the opinion to be given as part of the ordinary
exercise of his or her skill, knowledge, training and experience
while observing or participating in such events.
 If participant experts proffer opinion evidence extending
beyond these limits, they must comply with rule 53.03 “with
respect to the portion of their opinions extending beyond those
limits”: Westerhof, at para. 63. In acting as a gatekeeper, trial
judges have the important task of ensuring that participant
experts do not exceed their proper role or, if they do, that there is
compliance with rule 53.03.
 As indicated earlier, among other things, in his evidence
— identified the problems typical of survivors of childhood sex-
— testified about the negative impacts that Mr. Imeson’s experi-
ences of childhood abandonment and abuse had on his ability
to regulate emotional responses and his ability to establish
emotionally satisfying relationships, and he provided exam-
— expressed the opinion that it was “entirely possible” that Mr.
Imeson’s first murder occurred when he awoke from a black-
out to discover his victim performing fellatio on him, and
re-experiencing the sense of betrayal and rage he felt toward
his earlier abuser, he acted with disinhibited lethal violence.
 This opinion evidence from Dr. Smith’s reports was
repeated in his oral evidence. This evidence went to the issues of
whether the sexual assaults occurred and whether Mr. Imeson
suffered any harm as a result.
 The difficulty in this case was that there was no expert report
per se, nor were there any clinical notes or records. Dr. Smith’s opinions had to be gleaned from the reports he had prepared based on
the handwritten treatment notes he had destroyed. Mr. Imeson’s
counsel also identified additional opinions that she proposed to elicit
from Dr. Smith that were outside the scope of the reports.
 During the voir dire, Mr. Imeson’s counsel provided a highlighted version of the reports, identifying the “opinions” he appeared
to express. There was, however, no review of the specific opinions, or
of the contents of the reports, during the admissibility voir dire.
 Instead, after ruling that Dr. Smith would be able to testify
about “his observations of, impressions formed regarding and
treatment provided to the plaintiff as set out in the reports