Medical Expert Evidence Gone Wrong

By Megan Chan

In medical malpractice actions against physicians, a mere error of judgment will not be sufficient to yield damages in tort. Physicians may have differing opinions on treatment. If the error could be made while working within the standards of ordinary care, the error will not constitute negligence. An unfortunate outcome is not the measure of negligence, nor is it the measure of a breach of the standard of care.

However, if an error of judgment could not have been made by a reasonably competent physician with the skill and judgment of the defendant physician, then that error will be negligent.

In medical malpractice actions (which are generally complex matters), judges and juries lack the expertise necessary to assess causation, standard of care, and breach of the standard of care. As such, expert assistance is required and the absence of expert evidence in support of the plaintiff’s medical malpractice claim is fatal.

Factual findings regarding whether a breach of the standard of care occurred are primarily reliant on the credibility and reliability of the expert witnesses retained by the parties.

• Credibility is the witness’ willingness to tell the truth.
• Reliability is the accuracy of the witness’s testimony.
• Accuracy is affected by the witness’s ability to accurately observe, recall, and recount events. A witness who is not credible cannot be reliable, but a credible witness may still be unreliable.

In the recent decision Forget et al. v. Gibb et al., 2026 ONSC 626, the Ontario Superior Court addressed the importance of ensuring that counsel carefully select an expert who is aware of and understands the role of an expert in a medical malpractice trial.

Both the plaintiffs and the defendant retained general surgeons as expert witnesses. Although expert reports are exchanged and form the basis for examinations at trial, the expert’s testimony is what constitutes the evidence at trial (not their reports). 

Experts have a duty to provide the court with fair, objective, and non-partisan opinion evidence, and should not become advocates for the party by whom they are retained. If an expert fails to remain independent, the trial judge should exercise their gatekeeper function and exclude (in whole or in part) the expert’s unacceptable testimony.

A court should weigh the following factors when assessing the evidence of medical expert witnesses:

• The relevance of the training, expertise, and specialty of the witness to the medical issues before the court;
• Any reason for the witness to be less than impartial; and
• Whether that testimony appears credible and persuasive compared and contrasted with the other expert testimony at the trial.

The plaintiffs’ expert, Dr. Bahrami Shahi, had no previous experience providing expert medical evidence in the Superior Court of Justice, but was duly qualified to provide evidence as an expert witness on the basis of his background, education, and experience.

Unfortunately, the court found that Dr. Shahi did not provide evidence in a manner that was acceptable of an independent, unbiased, and objective expert.

Notably, Dr. Shahi stated that he did not consider the evidence provided within the transcripts of the defendant physician’s examination for discovery and believed that what was in the discovery was irrelevant to him. Dr. Shahi stated that he only relied on the relevant operative notes and medical records to form his expert opinion.

Dr. Shahi further consistently ignored the defendant physician’s evidence and favoured the plaintiff’s evidence, when there were differences between the two. This amounted to Dr. Shahi becoming an advocate on behalf of the plaintiff.  

Dr. Shahi also gave opinion evidence based on the outcome of the care, testifying that he knew that the defendant physician did not meet the standard of care because the surgery performed on the plaintiff had failed.

Dr. Shahi admitted that he did not pay much attention to the reliability of the articles he selected to cite in his expert report. He further stated that he “may choose to lie” and that he based his opinion on facts that are “professional”, not “judicial facts”, when asked about the significance of his sworn evidence.

Dr. Shahi demonstrated a misunderstanding of the concept of the standard of care, stating that “the standard of care is not necessarily mandatory”, that the standard of care was dictated by the outcome of the surgery, and that his assessment of the defendant physician’s care was premised on what he would have done personally, rather than what the standard of care required.

The court found that these decisions (among others) of Dr. Shahi constituted a fundamental misunderstanding of his duties and obligations as an expert witness.

Ultimately, the court stated that the circumstances would have permitted the exclusion of the entirety of Dr. Shahi’s evidence. Nevertheless, the court went on to address the alleged breaches of the standard of care throughout the court’s analysis of the defendant’s expert’s (Dr. Lloyd Smith) evidence.

The court found Dr. Smith to be an exceptional witness, noting that he was cautious, conscientious, and balanced in his approach, as well as that he did not assume or presume facts unless he was asked to respond to a hypothetical question. Dr. Smith maintained objectivity and independence. Dr. Smith understood that the outcome of a surgery does not determine the standard of care, and focused his opinion on the actions and methodology employed by the defendant physician in his care provided.  

The contrast between the experience in providing expert medical evidence and preparing expert reports was clear as between Dr. Shahi and Dr. Smith. While Dr. Shahi was providing expert evidence for the first time, Dr. Smith had been qualified by the Superior Court of Justice to provide expert medical evidence on three occasions, and had prepared around 50-60 expert reports in the past.

Given the importance of expert medical evidence in a medical malpractice case, in addition to ensuring that the expert has the appropriate background to be duly qualified on the relevant issues, thorough review of an expert’s background and experience in providing expert evidence is important to ensure that the expert understands their duties to the court.