What is the test for expert testimony in a medical malpractice action?

Expert evidence is essential in medical malpractice actions. It is well established that a plaintiff in a medical malpractice action cannot establish a breach of the standard of care without credible and reliable expert evidence supporting the alleged breach. In Reid v. Livingstone, [2004] O.J. No. 1477, at paragraph 12, Cameron J. expressed the proposition as follows: In order to establish whether the conduct of a person engaged in a technical occupation not within the expertise of the ordinary person, such as a doctor or nurse, met the standard of care required of them…the plaintiff must provide evidence of a person qualified and experienced in the field of the conduct at issue that the defendant’s conduct in the circumstances failed to meet the standard of care the defendant owed to the plaintiff.