The Court of Appeal for Ontario allowed an appeal in a medical negligence action, ordering a new trial.
The plaintiffs alleged delayed diagnosis of hydrocephalus in their child, leading to brain damage.
The trial jury found no breach of standard of care.
The appellate court found that the defendants' expert witness exceeded his role by opining on the credibility and reliability of the parties, thereby breaching his duty of independence.
The trial judge erred by not specifically instructing the jury to disregard these improper opinions and by failing to exclude them.
Despite the appellants' counsel not objecting at trial, the errors constituted a substantial wrong or miscarriage of justice, tainting the jury's verdict and warranting a new trial.