Westerhof v. Gee Estate, 2015 ONCA

Rule 53.03 applies to situations in which experts are being retained by a party for purposes of the litigation. The Rule does not apply to a participant expert.

A participant expert

  1. has special expertise and is giving an opinion based on the witness’ observation of or participation in the events at issue; and
  2. formed the opinion as part of the ordinary exercise of the witness’s skill, knowledge, training and expertise while observing or participating in the events.

 A treating physician is an example of a participant expert. That physician has formed an opinion of the issue not because the physician was asked by a party to testify, but because the physician had already documented the opinion in notes or summaries while treating a party.

The Rule also does not apply to the opinion of a non-party expert. A non-party expert forms an opinion based on personal observations or examinations relating to the subject matter of the litigation, but for purposes other than the litigation. A physician retained by an insurer not involved in the litigation (e.g. a statutory accident benefits insurer) is an example of a non-party expert