In Canadian medical malpractice law, the standard of care is almost always proved through expert evidence. The Supreme Court of Canada confirmed this in ter Neuzen v Korn, [1995] 3 SCR 674: medicine is a specialized field, and the question of whether a physician’s conduct fell below the standard of a reasonable practitioner is not, in most cases, a matter on which lay opinion is reliable. Without an expert to articulate the standard and identify the breach, a plaintiff’s case will usually fail.
There is a narrow exception. In ter Neuzen itself, at paragraph 55, the Court held that where the issue can be decided on the ordinary common sense of the trier of fact, expert evidence is not strictly required. The classic Canadian example is Anderson v Chasney, [1949] 4 DLR 71, in which a surgeon left a sponge inside a patient. Lay witnesses could describe what had happened. Common sense, not expert opinion, supplied the conclusion that it was negligent.
Drain v Ziesmann, 2023 MBKB 59 is a recent Manitoba decision that fits within that narrow exception.
The facts
In 2010, Melanie Drain underwent breast reduction surgery performed by Dr. Manfred Ziesmann. As is standard after that procedure, surgical drains were placed to remove fluid accumulating at the operative site.
At a follow-up visit, Dr. Ziesmann attempted to remove a drain from Ms. Drain’s left breast. According to the evidence the trial judge accepted, he pulled on the drain with substantial force, despite Ms. Drain’s increasing distress at the pain it was causing. The drain ultimately broke, leaving a portion retained in the breast tissue. Dr. Ziesmann did not acknowledge to Ms. Drain that the drain may have broken, and he did not arrange follow-up to confirm whether it had.
Ms. Drain sued for the harm caused by the retained drain fragment.
The trial decision
The trial judge in the Manitoba Court of King’s Bench found Dr. Ziesmann liable.
Critically, he did so without the benefit of expert evidence from the plaintiff. The plaintiff’s evidence consisted of her own testimony and that of lay witnesses. The defence called expert evidence, but the trial judge found that no expert evidence was needed for the plaintiff to make out her case.
The judge accepted the lay evidence that Dr. Ziesmann had “yanked on the drain despite [Ms. Drain’s] increasing upset at the force used and pain it was causing her” and that he “had to have realized there was a good possibility that his yanking on the drain caused it to break and yet he downplayed that possibility.”
He also rejected Dr. Ziesmann’s evidence at trial that he specifically remembered looking at the end of the drain and finding no problem with it: “I simply do not accept Dr. Ziesmann’s assertion, years after the fact, without supporting documentation, that he remembered looking at the end of the drain and that there was no problem with it.”
The conclusion the trial judge drew was straightforward. Forcefully pulling on a drain over a patient’s protest, breaking it, and then downplaying the obvious possibility of breakage, was conduct that fell below any reasonable standard. As a matter of common sense, it was negligent, and no expert evidence was needed to make that out.
The doctrinal context
The trial judge’s approach is consistent with the Canadian framework set out in ter Neuzen v Korn. The Court there accepted that the general rule in medical negligence is that expert evidence is required, while leaving room for cases in which the trier of fact can find negligence without it. The exception applies where the conduct is so obviously below any reasonable standard that lay assessment is reliable, “easily understood by the ordinary person.”
Ontario courts apply the same framework. The narrow exception captures cases like a sponge left in a surgical wound (Anderson v Chasney), wrong-site surgery, drug administration errors involving an obvious dosage mistake, and physical conduct that any layperson can evaluate. It does not capture cases that turn on diagnostic reasoning, treatment selection, surgical technique, or any clinical judgment of meaningful complexity. For those, expert evidence remains essential, and the general standard articulated in Crits v Sylvester, [1956] SCR 991 (every medical practitioner must exercise the degree of care and skill expected of a normal, prudent practitioner of the same experience and standing) requires expert articulation in almost every case.
Drain v Ziesmann is a useful illustration of where the line falls. The conduct at issue was physical, observable, and capable of being described by lay witnesses. The harm followed directly. There was no clinical judgment to evaluate, only a series of acts that the trial judge found unreasonable in the circumstances.
Why this case matters
For plaintiffs and their counsel. Drain is a reminder that the no-expert-evidence exception is real but narrow. In a small number of cases (retained surgical objects, wrong-site surgery, frank physical mishandling of the kind seen here) it may be possible to make out a claim on lay evidence alone. In the great majority of cases, expert evidence remains essential, and the early question for prospective claimants is almost always whether reasonable expert opinion will support the case. A claim that depends on the no-expert exception should be tested rigorously before being filed.
For defence counsel. Drain shows that strong post-hoc denials by the defendant physician will not save the day where the contemporaneous evidence (the patient’s account, the lay witnesses, the absence of supporting documentation) tells a different story. Where the conduct alleged is physical and observable, the credibility contest at trial often determines the outcome. Years-later assertions of recollection, unsupported by documentation, are vulnerable.
For patients. Most medical malpractice cases require expert evidence to succeed. That requirement is not arbitrary. It reflects the reality that medicine is a complex field and that what looks like negligence to a non-specialist may, on expert review, fall within the range of reasonable care. Drain is the rare exception, not the rule. If something has gone wrong with your care, the most useful first step is to consult an experienced medical malpractice lawyer who can identify, with the records and the right experts, whether the case is viable.
For more on how medical malpractice cases are built and tried in Ontario, see Suing for Medical Malpractice in Ontario: What You Need to Know. For information specific to surgical injury claims, see the Surgical Errors practice page.
Decision Date: March 23, 2023
Jurisdiction: Court of King’s Bench of Manitoba
Citation: Drain v Ziesmann, 2023 MBKB 59 (CanLII)
