Wilson v Swanson: Error in Judgment vs. Negligence and the Surgeon’s Intraoperative Decision

Medicine is practised in real time, with imperfect information, under the pressure of consequences that cannot be delayed. A surgeon opening a patient’s abdomen and looking at a lesion that may or may not be cancer cannot pause the moment, order further tests, and wait for a clearer picture. They must make a decision. They must make it now. And they must make it without any knowledge of whether, years later, a court will agree with them.

Canadian law has long recognized this reality, and Wilson v Swanson is the Supreme Court of Canada decision where that recognition received its most durable legal form. The case arose from a stomach operation in British Columbia in 1951. A skilled surgeon, Dr. Roger Wilson, believed the lesion he had exposed was malignant based on the clinical evidence before him, including a rapid pathological test reporting probable cancer. He operated accordingly, removing more tissue than would have been necessary for a benign growth. The lesion turned out to be benign. The patient, Swan Swanson, sued.

The Supreme Court of Canada found no negligence. But the significance of Wilson v Swanson lies far beyond its outcome for these particular parties. In allowing Dr. Wilson’s appeal and restoring the trial dismissal, Justice Rand articulated a principle that has been cited in virtually every Canadian medical malpractice case involving diagnostic or treatment decisions ever since: an error in judgment, made honestly and intelligently in the exercise of professional skill, is not the same thing as negligence. A physician who exercises reasonable care and does not arrive at the right answer has not necessarily failed in their legal duty. A physician who abandons reasonable care in making their decision has.

Understanding this distinction (where the line is drawn, how it is applied, and what its limits are) is essential to anyone navigating medical malpractice law in Canada.

The Legal Landscape: Why the Error in Judgment Distinction Exists

The Problem With Judging Medicine in Hindsight

The first and most fundamental reason Canadian law distinguishes between errors in judgment and negligence is the inherent danger of hindsight bias: the powerful human tendency to believe, after learning how events unfolded, that the outcome was foreseeable and therefore preventable.

Hindsight bias operates insidiously in legal proceedings. When a judge is told that a surgeon treated a lesion as malignant and it turned out to be benign, the knowledge of the outcome changes how the original clinical picture is perceived. Evidence that appeared genuinely ambiguous at the time of treatment looks, in retrospect, like evidence that pointed clearly in one direction. The surgeon who faced a genuinely difficult intraoperative differential looks, after the fact, like someone who should have known better.

If medical malpractice law permitted liability wherever a physician’s judgment turned out to be wrong, it would effectively transform medical practice into a guarantee of correct outcomes. No such guarantee is possible. Medicine involves uncertainty at every level: uncertainty in symptoms, uncertainty in the sensitivity and specificity of diagnostic tests, and uncertainty in the natural history of disease processes. A legal standard that equated bad outcomes with negligence would not improve medicine; it would drive physicians toward defensive practices that avoided necessary interventions.

The error in judgment doctrine exists to prevent this. It holds that the measure of a physician’s conduct is the quality of their decision-making process, assessed against the clinical circumstances as they existed at the time of the decision, not the correctness of the outcome assessed in the light of what was later discovered.

The Standard Against Which Decisions Are Measured

The governing standard of care in Canadian medical malpractice law requires a physician to exercise the skill, knowledge, and judgment of a reasonably competent practitioner in the same specialty and circumstances. Specialists are held to the standard of competent specialists in their field. The standard does not require perfection; it requires competence.

Within this framework, the error in judgment principle operates as a specific application to clinical decision-making under uncertainty. It asks: in making this decision (this diagnosis, this treatment choice, this intraoperative call), did the physician apply the skill, knowledge, and care of a reasonably competent practitioner? If yes, the fact that the decision turned out to be wrong does not establish negligence. The distinction is not between right decisions and wrong decisions. It is between decisions made with reasonable competence and decisions made without it.

The Case: Wilson v Swanson

Who the Parties Were

The case is named Wilson v Swanson, where Dr. Roger Wilson was the highly skilled surgeon and defendant-appellant, and Swan Swanson was the patient and plaintiff-respondent. The claim against Dr. Wilson was not that he had lacked technical skill in performing the operation. The claim was that he had made the wrong decision about what kind of operation to perform. That distinction, between technical execution and clinical judgment, is at the heart of what the case decided.

Swan Swanson’s Medical History and Presentation

Swan Swanson was sixty-seven years old at the time of the operation in April 1951. He had suffered from periodic indigestion for many years. His surgical history was relevant: in 1926 he had undergone a laparotomy, which ultimately resulted in the removal of his appendix. The following year, severe abdominal pains were relieved by another laparotomy and the severance of adhesions. Through the 1940s he suffered recurring episodes of indigestion accompanied by epigastric fullness and hunger pains. A prolonged buttermilk diet in 1947 had resolved the symptoms temporarily, but they returned in January 1951 with an ominous change: the pain now had a burning character, and between December 1950 and March 1951 Swanson had lost between fifteen and twenty pounds.

On March 26, 1951, Swanson was admitted to Galt Hospital in Lethbridge, Alberta, complaining of pains in the epigastrium (the upper central portion of the abdomen) along with fever and weakness. Dr. Johnson examined him and arranged a gastrointestinal series of X-ray plates. These revealed a filling defect on the lower third of the rear wall of the stomach. In the clinical context, the finding pointed toward gastric cancer. The provisional diagnosis was malignancy. The clinic was preparing Swanson for a laparotomy and gastric resection when he decided, for reasons unrelated to his medical care, to return to British Columbia and seek treatment there. The hospital provided him with his X-ray films.

From Lethbridge to Vancouver: Two Independent Cancer Diagnoses

In Vancouver, Swanson presented to the British Columbia Cancer Clinic associated with the Vancouver General Hospital. The clinic’s physicians conducted their own examination, reviewed the Lethbridge X-ray films, and reached the same conclusion: the provisional diagnosis was gastric cancer. Swanson was also examined that same day by Dr. Wilson himself, in the presence of the clinic’s Dr. Crawford. Having reviewed his own physical examination of the patient, the Lethbridge X-rays, Dr. Johnson’s letter, and Dr. Crawford’s examination findings, Dr. Wilson diagnosed probable cancer of the stomach and recommended an exploratory operation and removal of the growth if it proved operable. An intern who examined Swanson on admission to the Vancouver General Hospital also diagnosed probable stomach cancer.

Before Dr. Wilson even entered the operating theatre, three separate groups of qualified clinicians (in Lethbridge, at the BC Cancer Clinic, and at Vancouver General) had independently reached the same clinical conclusion: this was most likely cancer.

The Intraoperative Decision and the Frozen Section

The operation took place at the Vancouver General Hospital on April 23 or 24, 1951. When Dr. Wilson opened the abdomen and exposed the stomach, he found numerous adhesions fixing the stomach to the liver, the transverse colon, and the pancreas. On the posterior aspect of the stomach he felt a firm annular lesion adhering to the pancreas. The stomach was mobilized and opened. A large ulcer on the posterior wall was disclosed, involving the depth of the pancreas. Crucially, there was no gross visual evidence of malignancy.

Faced with this uncertainty, Dr. Wilson took a section of the ulcer and sent for Dr. Fidler, the hospital’s chief pathologist, whose eminence as a pathologist was unchallenged by all parties. Dr. Fidler came to the operating room and subjected the tissue to what is known as a frozen section test, a rapid pathological examination that can be completed in fifteen to twenty minutes, though it cannot provide a conclusive result. A conclusive determination would require the paraffin wax method, which could not be completed in less than twenty-four hours. Dr. Fidler’s frozen section reported that malignancy was probably present, of a type known as linitis plastica.

Dr. Wilson now faced a genuine dilemma with significant consequences on both sides. If he accepted the probable malignancy finding and proceeded with the radical resection, he would remove tissue that did not need to be removed if the lesion proved benign, but he would maximise the prospect of completely eradicating a cancer if it existed. If he paused, closed the abdomen, waited twenty-four hours or more for the conclusive paraffin test, and reopened in a second operation if malignancy was confirmed, he would spare unnecessary tissue if the lesion was benign, but expose Swanson to the risks of two major operations rather than one, and, if the lesion was truly malignant, risk allowing the cancer to progress during the interval.

Dr. Wilson chose to proceed. He removed the entire spleen, approximately four-fifths of the stomach, and between two-thirds and three-quarters of the pancreas: the procedure appropriate for confirmed malignancy. At the suggestion of Dr. Fidler, who examined the removed stomach and reiterated his opinion that the lesion was probably malignant, a further two inches of stomach beyond what Dr. Wilson had initially thought necessary was also removed.

The final paraffin wax test, completed after the operation, established that the lesion was not malignant. It was a benign ulcer. The more extensive surgery had been unnecessary.

The Aftermath

Swanson experienced post-operative complications but ultimately recovered and was discharged from hospital on May 31, 1951. As a result of the removal of a portion of the pancreas, he developed mild diabetes. He sued Dr. Wilson for negligence. The trial was held approximately four years later, in March 1955. Swan Swanson died before the appeal to the Supreme Court of Canada was heard.

The Journey Through the Courts

The Trial: British Columbia Supreme Court Dismisses the Action

The British Columbia Supreme Court at trial dismissed Swanson’s action. The trial judge found that Dr. Wilson had exercised reasonable clinical judgment in treating the lesion as malignant. The independent provisional diagnoses made by three separate groups of clinicians before surgery were significant: Dr. Wilson was not acting idiosyncratically. He was acting consistently with a clinical consensus built from multiple independent assessments of the same clinical picture. The trial judge found not only that Swanson had failed to establish a prima facie case of negligence but that there had been no negligence at all.

The Court of Appeal: Reversal

The British Columbia Court of Appeal, in reasons delivered by Coady J.A., reversed the trial judgment and found Dr. Wilson negligent. The Court of Appeal gave significant weight to the evidence of Dr. Kemp, who testified as an expert witness for Swanson. Dr. Kemp stated that, had Swanson been his patient, he would have conducted certain additional pre-operative tests before making a clinical diagnosis (including a test of the gastric juices, a blood count, fresh X-rays, and a radiologist’s report) that in his view would have assisted in determining the character of the lesion. The Court of Appeal concluded that the failure to conduct these tests represented a departure from the appropriate standard of care.

Dr. Wilson appealed to the Supreme Court of Canada.

The Supreme Court of Canada: Restoration of the Trial Judgment

The Supreme Court allowed the appeal three to two. Rand J. wrote the majority, joined by Nolan J. Abbott J. concurred. Kerwin CJ and Locke J. dissented, each agreeing with the Court of Appeal’s conclusion. The majority restored the trial judge’s dismissal and found no negligence.

Justice Rand’s Judgment: The Foundational Articulation

The Expert Evidence Problem

Justice Rand, one of the most distinguished jurists in the history of the Supreme Court of Canada, began his analysis with a careful and pointed assessment of Dr. Kemp’s evidence. Kemp was a general practitioner in Vancouver who had worked as a certified anaesthetist at the Vancouver General Hospital from 1920 to 1938. He had subsequently worked for the Workmen’s Compensation Board and then entered general practice. He had never practised as a surgeon, was not a pathologist, and stated in cross-examination that he had never suggested he was an authority on gastric disorders.

Rand J. examined each of the pre-operative tests Dr. Kemp said he would have ordered (fluoroscopic assessment, gastroscopic examination, hydrochloric acid content of the stomach, lactic acid testing, occult blood measurement, blood count) and found that none of them would have provided useful information about the character of the lesion. The hydrochloric acid test, far from being a reliable indicator of malignancy, was present in early carcinoma in 50 percent of cases and its presence or absence was acknowledged to yield no dependable assistance. The blood count, done two days after surgery, showed 81 percent haemoglobin, not a significant anaemia. The other tests were equally unreliable for distinguishing malignant from benign growths.

Rand J.’s overall assessment of Dr. Kemp’s evidence was direct: “I can only describe the opinions which it embodies as a collection of elementary views on the diagnosis of cancer by one who is a virtual stranger to the exercise of such a medical and surgical judgment.” Dr. Kemp nowhere suggested that surgeons of Dr. Wilson’s rank would, in the same circumstances, have followed the course he outlined, or that any considerable number of competent surgeons would not have done what Dr. Wilson did.

By contrast, Dr. Palmer, a witness accepted by Dr. Kemp himself as of outstanding competency, gave evidence that focused the question in its real dimensions. The alternatives facing Dr. Wilson were to postpone the radical excision and run the risk of post-operative complications from a second operation (which actually followed in any event) and the serious possibility of aggravating a malignancy, or to act on his and Dr. Fidler’s best judgment. Dr. Palmer’s view was that the difference between the impairment caused by the admittedly necessary resection and the fuller resection carried out could be disregarded where there was good cause, and such cause existed in avoiding action that might have had fatal results for Swanson.

The Central Principle

Having assessed the expert evidence, Rand J. articulated the governing legal standard. A surgeon, by his ordinary engagement with a patient, undertakes that he possesses and will faithfully exercise “the skill, knowledge and judgment of the generality or average of the special group or class of technicians to which he belongs.” The question is not whether the outcome was correct. In a situation of genuine uncertainty, the question is whether the decision reflected the honest exercise of that professional intelligence.

At pages 811 to 813 of the report, Rand J. stated what has become the governing principle of the doctrine in Canadian malpractice law:

“An error in judgment has long been distinguished from an act of unskilfulness or carelessness or due to lack of knowledge. Although universally-accepted procedures must be observed, they furnish little or no assistance in resolving such a predicament as faced the surgeon here. In such a situation a decision must be made without delay based on limited known and unknown factors; and the honest and intelligent exercise of judgment has long been recognized as satisfying the professional obligation.”

And on the test itself:

“[W]hat standard does the law require of him in meeting it?… The test can be no more than this: was the decision the result of the exercise of the surgical intelligence professed? Or was what was done such that, disregarding it may be the exceptional case or individual, in all the circumstances, at least the preponderant opinion of the group would have been against it? If a substantial opinion confirms it, there is no breach or failure.”

Applied to Dr. Wilson’s decision, the answer was that his conduct did not fall outside the range of what a competent surgeon would have done. No attempt had been made to show that the completed operation was not within those limits. Dr. Palmer had expressly approved it. Dr. Fidler, standing at the highest level of pathologists, had both guided the decision and confirmed it. The suggestion by Dr. Kemp of what he personally would have done reflected nothing more than his own preference: it did not establish that Dr. Wilson’s approach fell below the standard of a reasonably competent surgeon in the same specialty.

Justice Abbott’s Concurrence

Justice Abbott concurred in the result, delivering separate reasons that expressly articulated the specialist standard of care which was then being settled in the companion case of Sylvester v Crits. He stated that the medical practitioner “must possess and use that reasonable degree of learning and skill ordinarily possessed by practitioners in similar communities in similar cases” and that “it is the duty of a specialist such as appellant, who holds himself out as possessing special skill and knowledge, to have and exercise the degree of skill of an average specialist in his field.” Applying this standard, Abbott J. was satisfied that in making the difficult intraoperative decision, Dr. Wilson exercised his best judgment in what he considered to be the best interest of his patient.

The Dissent: Kerwin CJ and Locke J.

Kerwin CJ and Locke J. each dissented, each agreeing with the BC Court of Appeal that the surgeon had been negligent. Kerwin CJ stated that his dissent was for the reasons given by Coady J.A. in the Court of Appeal. Locke J. similarly agreed with the Court of Appeal’s analysis. The existence of a genuine and reasoned dissent by two members of the Court, including the Chief Justice, illustrates that the facts of Wilson v Swanson were not trivially one-sided. The 3-2 majority makes the principles it established more significant: they resolved a genuinely contested question, not an easy case.

The Principle the Case Establishes: Three Dimensions

Dimension One: The Quality of the Process, Not the Correctness of the Outcome

The most fundamental aspect of the error in judgment doctrine is its focus on the quality of the clinical decision-making process rather than the correctness of the outcome. A physician is not a guarantor of results. Medicine does not offer certainty; it offers informed judgment. The law recognizes this by measuring a physician’s conduct against the process they employed (the skill, knowledge, and care they brought to their decision) rather than against the result that decision produced.

This means a physician who follows a reasonable diagnostic or treatment pathway may not be found negligent even when the pathway leads to a wrong answer, provided the pathway reflected the exercise of requisite competence. Conversely, a physician who follows an unreasonable pathway and happens to reach a correct answer has still been negligent: the standard is violated by the process, not absolved by the outcome.

Dimension Two: The Prospective, Not Retrospective, Assessment

The standard of care in medical malpractice must be assessed prospectively (from the perspective of what a reasonable physician would have known and done at the time of the treatment decision) not retrospectively, with the benefit of information that became available only later.

This principle was confirmed by the Supreme Court of Canada in Lapointe v Hôpital Le Gardeur, [1992] 1 SCR 351, where Justice L’Heureux-Dubé, writing for the Court, cited Wilson v Swanson as foundational authority and warned directly against the use of hindsight in medical malpractice assessment. The standard of care must be assessed in the context of the facts as they were known, or ought reasonably to have been known, at the time of treatment. A decision that was reasonable on the information available to the physician at the time is not made unreasonable by the subsequent emergence of information pointing in a different direction.

In Wilson v Swanson, this prospective assessment was central to the majority’s reasoning. Looking at the case as it appeared during surgery (three independent clinical assessments had reached the same provisional cancer diagnosis, Dr. Fidler’s frozen section reported probable malignancy, and the intraoperative appearance was genuinely ambiguous), Dr. Wilson’s decision was made on the basis of information that reasonably supported it. The fact that pathology later demonstrated the lesion was benign did not rewrite the clinical picture as it existed when the decision had to be made.

Dimension Three: The Range of Reasonable Practice

The standard of care in medicine is not a single point but a range. In many clinical situations, multiple approaches are recognized as reasonable by competent practitioners. A physician who chooses one medically defensible approach among several is exercising clinical judgment within the range of acceptable practice, even if another competent physician would have chosen differently.

This is what Justice Rand was addressing when he observed that evidence showing a physician did not use the same measures another physician would have used tends to prove errors of judgment, which do not create liability, as much as it tends to prove negligence. Expert evidence of a different preference does not establish that the preference not taken was required. Only when a physician’s approach falls outside the range of what any reasonable practitioner would endorse, when it reflects a departure from, rather than a variation within, the standard of care, does evidence of different practice become evidence of negligence.

The Line Between Error and Negligence: Where It Sits

What Takes a Decision Outside the Protection of the Doctrine

The error in judgment doctrine has a firm boundary. It does not protect decisions made through unskillfulness, carelessness, or lack of knowledge. A clinical decision becomes negligent, rather than merely mistaken in judgment, when:

• It is made without the knowledge a competent practitioner would have brought to it. A gap in foundational clinical knowledge that the standard of care required the physician to have is negligence, not a judgment error.
• It is made without the care a competent practitioner would have exercised. Failing to review available test results, dismissing critical information without consideration, or failing to recognize warning signs that the standard of care requires recognition of: these are failures of care, not exercises of judgment.
• It selects an option that no competent practitioner would have chosen on the available evidence. There is a range of defensible clinical choices in most situations. A decision entirely outside that range is negligence, not a judgment call.
• It follows an established clinical protocol that is itself demonstrably unsafe. As the SCC later confirmed in Ter Neuzen v Korn [1995] 3 SCR 674, common practice is not always a defence where that practice is demonstrably unsafe in ways that ought to be apparent to any careful practitioner.

The Contextual Specificity of the Operating Theatre

The error in judgment doctrine carries particular force in precisely the kind of situation Dr. Wilson faced: an intraoperative decision under real-time conditions, where the clinical picture presented a genuinely ambiguous differential diagnosis, where a rapid but non-conclusive pathological test had reported probable malignancy, and where the consequences of failing to treat a malignancy aggressively were potentially fatal. The surgeon who must choose, in the operating theatre, between an immediate radical resection based on a “probable” malignancy report and a less extensive procedure followed by a 24-hour wait for a conclusive test is not in the same epistemic position as someone reviewing a completed file in an outpatient setting.

The time-pressure and information-constraint of the intraoperative environment are themselves part of the “circumstances” against which the reasonableness of the decision is measured. Wilson v Swanson established that courts must assess the decision in its actual environment (including its pressures, constraints, and the genuine uncertainty present at the moment of decision) rather than in the idealized environment that hindsight creates.

The Common Practice Consideration

Where a physician’s approach reflects what a substantial body of competent practitioners in the same specialty would have done in the same situation, this is powerful evidence that the decision was within the range of reasonable judgment. In Wilson v Swanson, the convergence of three independent clinical assessments on the same provisional cancer diagnosis before surgery was, in effect, evidence that proceeding on that diagnosis was within common clinical practice. Dr. Wilson was not departing from professional consensus; he was acting consistently with it. And Dr. Palmer, whose outstanding competency was accepted even by Swanson’s own expert, expressly approved the course of action Dr. Wilson had followed.

Wilson v Swanson in the Modern Malpractice Landscape

The Doctrine’s Continued Authority

Justice Rand’s formulation, that “an error of judgment has long been distinguished from an act of unskilfulness or carelessness or due to lack of knowledge” and that “the honest and intelligent exercise of judgment has long been recognized as satisfying the professional obligation,” appears consistently in Canadian judgments, expert reports, and submissions across every area of medical malpractice law for nearly seven decades.

Its reinforcement in Lapointe v Hôpital Le Gardeur in 1992 explicitly connected the doctrine to hindsight bias and confirmed that prospective assessment of the standard of care is not merely a feature of the error in judgment defence but a foundational requirement of malpractice analysis generally. A court that evaluates a physician’s conduct as though they had access to information not available at the time of treatment has applied the wrong standard, regardless of which party that error benefits.

How the Doctrine Operates in Practice

The error in judgment defence is most powerfully available where:

• The decision was made in a situation of genuine clinical uncertainty, where the evidence available at the time reasonably supported more than one diagnostic or treatment conclusion
• The physician’s decision was consistent with what a significant body of competent practitioners in the same specialty would have done in the same situation
• The physician applied appropriate clinical reasoning to the available information
• The plaintiff’s expert evidence establishes only that another physician would have made a different decision, not that what was done fell outside the range of defensible practice
• The outcome that makes the decision look wrong in retrospect was not predictable with certainty at the time

Conversely, the doctrine provides little protection where:

• The clinical picture was not genuinely ambiguous and a reasonably competent physician would have recognized the correct diagnosis or treatment on the available information
• The physician failed to gather information they were required to gather before deciding
• The decision departed from established clinical protocols applicable to the situation
• No competent practitioner in the same specialty would have made the same decision on the same facts
• The decision was not a matter of clinical judgment at all but of basic care and attention any reasonably careful practitioner would have provided

Diagnostic Failure Cases: Where the Doctrine Is Most Tested

The error in judgment doctrine is most frequently and intensely litigated in diagnostic failure cases, the category of malpractice claims where a physician failed to diagnose a condition that was later found. These cases have an inherent hindsight problem: after diagnosis, the clinical signs that were present earlier often appear, in retrospect, to have pointed clearly toward the diagnosis that was missed. Wilson v Swanson is a direct counter to this tendency.

A cancer not diagnosed because the physician failed to order any investigation of a clear warning sign is a different case from a cancer not diagnosed because multiple competent practitioners assessed a genuinely ambiguous clinical picture and reached the same wrong conclusion. In the first, the error in judgment doctrine does not protect the physician: the failure to investigate was a departure from the standard of care, not an exercise of judgment within it. In the second, the doctrine applies directly: the physicians involved made honest and competent assessments that the information available to them supported, and the fact that the information proved insufficient to reveal the truth does not make those assessments negligent.

Distinguishing between these two scenarios in litigation requires expert evidence, not on whether the diagnosis was ultimately wrong, but on whether the process of clinical reasoning that led to it reflected the level of skill and care a competent practitioner in the same specialty would have applied.

The Relationship with Informed Consent

The error in judgment doctrine addresses the physician’s liability for the clinical decision itself. The informed consent framework, established in Hopp v Lepp, 1980 CanLII 14 (SCC) and Reibl v Hughes, 1980 CanLII 23 (SCC), addresses the patient’s right to participate in making that decision. These are distinct but complementary legal inquiries. A physician who makes a clinical decision within the range of reasonable judgment has satisfied the standard of care for the decision, but may still be liable for a consent failure if they made that decision without disclosing the material risks of the available options to the patient.

Wilson v Swanson predates the modern informed consent framework by a quarter century, and consent was not directly in issue in the case. But the two bodies of doctrine jointly define the full scope of a physician’s legal obligations: to exercise honest and competent judgment in making clinical decisions, and to ensure patients have the information they need to participate meaningfully in decisions about their own care.

Conclusion: The Dignity of Honest Clinical Judgment Under the Law

Wilson v Swanson is, at its core, a decision about what the law can reasonably demand of those who practise medicine. It acknowledges that physicians operate in the domain of biological complexity and human uncertainty, and that demanding correct outcomes rather than careful processes would not improve medicine; it would make honest practice impossible.

Justice Rand’s formulation, that the honest and intelligent exercise of judgment satisfies the professional obligation, is an expression of this acknowledgment with legal precision. It does not excuse negligent physicians. It does not protect carelessness, unskillfulness, or lack of knowledge. It protects the physician who looks at a genuinely ambiguous clinical picture, applies the best knowledge and judgment available, acts on the best information at hand (including a respected pathologist’s report of probable malignancy) and arrives at a conclusion that proves wrong. This physician has done what medicine requires of them.

Nearly seventy years after Justice Rand wrote these principles, Canadian courts continue to cite them because the clinical realities that motivated them have not changed. Medicine remains uncertain. Clinical decisions remain necessary. And the need to assess those decisions fairly, prospectively, in their actual context, without the distorting lens of known outcomes, remains as important as it was when Dr. Wilson stood at an operating table in Vancouver and made the best call he could.

Quick Reference: Wilson v Swanson and the Error in Judgment Doctrine

Citation and Court

• Wilson v Swanson, 1956 CanLII 1 (SCC), [1956] SCR 804
• CanLII: https://canlii.ca/t/1nlkb | Decided: October 1956
• Supreme Court of Canada | Present: Kerwin CJ and Rand, Locke, Abbott and Nolan JJ.
• Majority: Rand J. (Rand and Nolan JJ.) | Concurring: Abbott J. | Dissenting: Kerwin CJ and Locke J.
• On appeal from: Court of Appeal for British Columbia
• Outcome: Surgeon’s appeal allowed 3-2; trial dismissal restored; no negligence

The Parties

• Defendant-Appellant: Dr. Roger Wilson, highly skilled surgeon
• Plaintiff-Respondent: Swan Swanson, 67 years old at time of operation, patient; died before the SCC appeal was heard

Key Facts

• Swan Swanson presented in 1951 with stomach complaints; three independent groups of clinicians (in Lethbridge, at the BC Cancer Clinic, and at Vancouver General Hospital) independently diagnosed probable gastric cancer before surgery
• During surgery, Dr. Wilson found no gross visual evidence of malignancy; he sent for Dr. Fidler, the hospital’s chief pathologist, who performed a frozen section test (15-20 minutes, non-conclusive)
• Dr. Fidler reported malignancy was “probably present”; a conclusive paraffin wax test would have required 24 hours
• Dr. Wilson proceeded with a radical resection: entire spleen, approximately four-fifths of the stomach, and two-thirds to three-quarters of the pancreas
• The post-operative conclusive test showed the lesion was benign; Swanson developed mild diabetes from removal of the pancreatic portion
• Trial dismissed the action; Court of Appeal reversed; SCC restored the dismissal

The Governing Principle (Rand J.)

• “An error in judgment has long been distinguished from an act of unskilfulness or carelessness or due to lack of knowledge… the honest and intelligent exercise of judgment has long been recognized as satisfying the professional obligation.”
• The test: was the decision the result of the exercise of the surgical intelligence professed? Or was it such that, in all the circumstances, at least the preponderant opinion of the group would have been against it?
• Evidence that another physician would have done something differently proves only a difference in professional judgment; it does not, without more, prove negligence
• A physician who exercises reasonable skill and care in making a clinical decision is not negligent simply because the decision turns out to be wrong

What the Doctrine Protects

• Clinical decisions made honestly and competently in situations of genuine uncertainty
• Decisions within the range of what competent practitioners in the same specialty would have done on the available information
• Intraoperative and real-time decisions made under clinical time pressure, including decisions influenced by a rapid but non-conclusive pathological test reporting probable pathology
• Diagnostic conclusions that reflect the reasonable interpretation of available evidence, even when that evidence proves insufficient to reveal the correct answer

What the Doctrine Does Not Protect

• Decisions made through unskillfulness, carelessness, or lack of required knowledge
• Decisions that no competent practitioner in the same specialty would have endorsed on the same evidence
• Failures to gather information the standard of care required before deciding
• Departures from established clinical protocols applicable to the situation
• Decisions assessed retrospectively in the distorting light of known outcomes rather than prospectively in the clinical context at the time

Key Subsequent and Related Authority

• Lapointe v Hôpital Le Gardeur, [1992] 1 SCR 351. L’Heureux-Dubé J.; cited Wilson v Swanson as foundational; confirmed standard of care must be assessed prospectively, not with hindsight; courts must guard against assessing physician conduct in light of subsequently known outcomes
• Ter Neuzen v Korn, [1995] 3 SCR 674. This confirmed that following common medical practice is not always a defence where the practice itself is demonstrably unsafe in ways a careful practitioner ought to recognize
• Hopp v Lepp, 1980 CanLII 14 (SCC), [1980] 2 SCR 192 https://canlii.ca/t/1mjv6. This establishes the informed consent framework that operates alongside the error in judgment doctrine
• Reibl v Hughes, 1980 CanLII 23 (SCC), [1980] 2 SCR 880. This sets out the patient-centred disclosure standard and modified objective causation test