Hemmings v Peng: When the Anaesthetic, Not AFE, Caused the Catastrophe

A young mother undergoing routine caesarean section suffers cardiac arrest, profound anoxic brain injury, and lifelong catastrophic disability. Damages are agreed or assessed at twelve million dollars. The defence theory is that the catastrophe was caused not by anything the treating anaesthesiologist did or failed to do but by amniotic fluid embolism, a rare obstetric emergency that cannot be predicted or prevented. The plaintiff theory is that the anaesthesiologist failed to properly assess the airway, inappropriately converted from spinal to general anaesthesia, encountered a difficult intubation, and produced the hypoxia and hypotension that caused the cardiac arrest. The trial judge must choose between the two theories. That choice — between negligent cause and non-negligent cause — is doctrinally one of the most consequential a malpractice trial judge ever makes.

Hemmings v Peng, 2024 ONCA 318, is the Court of Appeal for Ontario’s recent affirmance of a $12 million plaintiff trial judgment arising from exactly this choice. The trial judge rejected the AFE defence and accepted the anaesthetic accident theory. The Court of Appeal applied the Housen v Nikolaisen, 2002 SCC 33, palpable and overriding error standard and found no basis to disturb the trial finding. The appeal was dismissed.

The case is doctrinally important for several reasons. It is the third clean appellate affirmance of a plaintiff trial victory in the rewritten case-comment cluster on this site — substantially balancing the previously defence-heavy appellate jurisprudence. It articulates the causation-by-elimination framework that operates when defendants propose non-negligent alternative causes. It introduces AFE doctrine and the limits of the AFE defence. It engages the difficult airway management standard of care and the “last resort general anaesthesia” framework in caesarean section practice. And it sits as the second anaesthesia case in the cluster, providing important balance to Williamson v Wang (BC, defendant win, equipment breakage).

This is also a case with a difficult human dimension. Ms. Hemmings was twenty-nine years old when she went into hospital for the birth of her child. She came out with catastrophic brain injury. The lawsuit was pursued by her family on her behalf. Behind the doctrinal framework lies the reality of a young life altered forever in the course of a routine procedure.

The clinical context: obstetric anaesthesia for caesarean section

Caesarean section is one of the most common major surgical procedures performed in Canada. Approximately one in three deliveries is by caesarean section, with regional and clinical variation. The procedure is performed under three principal anaesthesia approaches:

Spinal anaesthesia. A single injection of local anaesthetic into the cerebrospinal fluid in the lumbar subarachnoid space. Produces rapid onset of dense anaesthesia in the lower abdomen. The standard approach for planned caesarean section in modern Canadian practice. Patient remains conscious.

Epidural anaesthesia. A catheter placed in the epidural space allowing continuous or repeated administration of local anaesthetic. Often used for labour analgesia; can be extended or converted for caesarean section. Patient remains conscious.

General anaesthesia. Loss of consciousness with airway management (typically endotracheal intubation). Reserved for specific indications.

The strong preference for regional anaesthesia in caesarean section reflects several considerations:

• Maternal consciousness allows immediate bonding with the infant and active participation in the experience of birth
• Lower aspiration risk. Pregnant women have delayed gastric emptying, lower esophageal sphincter incompetence, and increased intra-abdominal pressure. They are considered to have a “full stomach” regardless of fasting status. General anaesthesia with intubation carries higher aspiration risk in this population.
• Lower difficult-airway risk. Pregnancy produces airway edema, increased mucosal vascularity, weight gain, and increased breast size — all of which can complicate intubation. The incidence of difficult intubation in obstetric anaesthesia is higher than in non-obstetric populations.
• Reduced neonatal sedation. General anaesthetic agents cross the placenta and can produce neonatal sedation requiring resuscitative support.
• Generally faster maternal recovery.

Indications for general anaesthesia in caesarean section include:

• Failed regional anaesthesia
• Coagulopathy contraindicating regional
• Inability to position the patient for regional
• Maternal refusal of regional after appropriate counselling
• Time-critical emergency where regional cannot be established quickly
• Specific contraindications to regional in the individual patient

Patient agitation alone during regional anaesthesia is generally not a sufficient indication for conversion to general. Agitation can typically be managed with reassurance, block adjustment, small doses of supplementary intravenous analgesia or anxiolysis, or position changes. Conversion to general anaesthesia is a measured clinical decision based on specific indication, not a reflexive response to patient distress.

Combined spinal and general anaesthesia — which is what occurred in Hemmings — has particular hemodynamic implications. Spinal anaesthesia produces sympathetic blockade and reduced systemic vascular resistance. General anaesthetic agents (particularly propofol used for induction) produce vasodilation and myocardial depression. The combination compounds hypotension. Where the patient also has compromised oxygenation from a difficult intubation, the hemodynamic challenge becomes severe.

The clinical context: Amniotic Fluid Embolism (AFE)

AFE is an obstetric emergency in which amniotic fluid material enters the maternal circulation, producing a syndrome of sudden cardiovascular collapse, hypoxia, and coagulopathy. Key clinical features:

Incidence. AFE is extraordinarily rare. Estimates vary across the literature, but a frequently cited incidence is approximately 1 in 40,000 deliveries. The condition is not predictable or preventable; no test identifies at-risk patients in advance.

Pathophysiology. The pathophysiology is debated. Earlier theories proposed mechanical embolism of amniotic fluid material into the maternal pulmonary circulation. Current thinking is more consistent with an anaphylactoid response — the maternal immune system reacting to amniotic fluid components with massive vasoactive mediator release, producing the cardiovascular and coagulopathy effects.

Timing. AFE typically occurs during labour, delivery, or the immediate postpartum period (usually within 30 minutes of delivery).

Classic clinical features (Clark criteria). The Clark diagnostic criteria, widely used in research and increasingly in clinical practice, require:

• Acute hypotension or cardiac arrest
• Acute hypoxia (dyspnea, cyanosis, respiratory arrest)
• Coagulopathy (disseminated intravascular coagulation) or severe clinical hemorrhage in the absence of other explanation
• All occurring during labour, caesarean section, or within 30 minutes postpartum
• No other clinical condition or potential explanation for the signs and symptoms

The coagulopathy/DIC feature is particularly important. In the great majority of AFE cases, coagulopathy is present and is a defining feature of the syndrome. Cases without coagulopathy can still be AFE but the diagnosis is less secure without this feature.

Diagnosis. AFE is a diagnosis of exclusion. No specific test confirms the diagnosis. The diagnosis depends on the clinical features and the exclusion of other identifiable causes.

Mortality. Historically very high (60-80% maternal mortality). Modern critical care has improved outcomes but mortality remains substantial (20-50% in current series).

Treatment. Aggressive resuscitation, fluid management, blood products for coagulopathy, supportive intensive care. Specific therapies remain limited.

Prevention. None. AFE cannot be predicted, prevented, or anticipated.

The clinical features of AFE matter for litigation purposes. Where a cardiac arrest during obstetric care has features consistent with AFE — sudden onset, severe hypoxia, coagulopathy, no other explanation — the AFE diagnosis is plausible and the defence may succeed. Where features are inconsistent — gradual progression following identifiable interventions, absence of coagulopathy, identifiable alternative cause — the AFE defence faces evidentiary challenges. Hemmings is a case in which several Clark criteria were not satisfied, and the trial judge found AFE unlikely.

The substantive facts

Ms. Hemmings was twenty-nine years old. On April 20, 2009, she presented at Scarborough General Hospital for a caesarean section. The procedure was performed under the care of an obstetric and anaesthesia team that included Dr. Jamensky as the attending anaesthesiologist.

The intraoperative sequence, as found by the trial judge (at paragraph 213 of the trial decision), was as follows:

1. Spinal anaesthesia was administered. This is the standard approach for planned caesarean section and is typically expected to provide adequate analgesia for the procedure.
2. The patient became agitated after the initial surgical incision. Agitation after the initial incision can occur for various reasons — inadequate block, anxiety, intraoperative awareness of pressure or manipulation even without pain, position-related discomfort. The clinical assessment of agitation should distinguish among these causes because the management differs.
3. The decision was made to convert from spinal to general anaesthesia. This decision is the first identified breach in the trial finding. Expert testimony established that general anaesthesia should be a last resort in caesarean section. The trial judge found that the agitation alone, without specific indication for general, did not meet the threshold for conversion.
4. During induction of general anaesthesia, Dr. Jamensky encountered difficulty intubating the patient. The first attempt to intubate failed. A second attempt with a larger blade succeeded, but significant time elapsed during the difficult intubation.
5. Oxygen levels and blood pressure dropped during the difficult intubation. The combination of spinal anaesthesia (already producing sympathetic blockade and reduced systemic vascular resistance), the general anaesthetic induction agents (producing vasodilation and myocardial depression), and the prolonged hypoxia during the difficult intubation, together produced severe cardiovascular compromise.
6. Ms. Hemmings suffered a cardiac arrest. Resuscitation efforts were performed but the period of cardiovascular collapse and inadequate cerebral perfusion produced profound anoxic brain injury.

The resulting brain injury was catastrophic. The action was pursued on behalf of Ms. Hemmings by her mother, sister, daughter, and son as litigation guardians.

The competing causal theories at trial

The trial proceeded as a contest between two distinct causal theories.

The plaintiff’s theory: anaesthetic accident or complication.

The plaintiff identified specific breaches of the standard of care:

• Failure to properly assess Ms. Hemmings’ airway preoperatively
• Inappropriate conversion from spinal to general anaesthesia (the threshold for conversion was not met)
• Inadequate management of the difficult intubation when it occurred

The causal chain: improper airway assessment led to under-preparation for the difficulties of intubation; inappropriate conversion to general anaesthesia exposed the patient to the cardiovascular and airway risks of general; the combined hemodynamic effects of spinal plus general produced hypotension; the difficult intubation produced hypoxia; the combination of severe hypotension and prolonged hypoxia produced cardiac arrest; the cardiac arrest produced the anoxic brain injury.

The defence theory: Amniotic Fluid Embolism (AFE).

The defendant physicians proposed AFE as the cause of the cardiac arrest. On this theory, the cardiac arrest was the consequence of an unpreventable obstetric emergency that would have occurred regardless of any aspect of the anaesthesia management. AFE is, by its nature, a non-negligent cause — it cannot be predicted, prevented, or caused by any clinical decision.

The theories were mutually exclusive in the practical sense. The cardiac arrest had one underlying cause. That cause was either an anaesthetic accident (which implicated the anaesthesiologist’s standard of care) or an AFE (which did not). The trial judge had to choose between the two.

The trial judge’s analysis

Rejection of AFE. The trial judge found AFE unlikely as the cause based on several factors:

• AFE is extraordinarily rare. The prior probability is low.
• AFE is a diagnosis of exclusion. Where an identifiable alternative cause exists (here, the anaesthetic management), AFE is the less likely explanation.
• Coagulopathy is a typical feature of AFE. The patient did not have coagulopathy or DIC. This absence is significant evidence against the AFE diagnosis.
• Expert testimony from Dr. Barrett, the plaintiff’s obstetrical expert, supported the rejection of AFE based on the clinical features.
• Even defence anaesthesia experts substantially supported the exclusion of AFE in their testimony.

Acceptance of anaesthetic accident. The trial judge accepted that the cardiac arrest was caused by the combined effects of:

• The spinal anaesthesia’s hemodynamic effects (sympathetic blockade, reduced systemic vascular resistance)
• The general anaesthetic induction’s hemodynamic effects (vasodilation, myocardial depression)
• The prolonged hypoxia from the difficult intubation

Expert testimony from Dr. Goldszmidt explained how the combined spinal and general anaesthesia produced hypotension and how the difficult intubation produced hypoxia, and how the combination caused the cardiac arrest. The trial judge accepted this analysis.

Causation under Clements v Clements. The trial judge applied the but-for causation framework from Clements v Clements, 2012 SCC 32. The question: but for the breach, would the harm have occurred? The trial judge found that without the general anaesthetic, the cardiac arrest would not have occurred. The general anaesthetic was not necessary in the circumstances (the inappropriate conversion was a breach). The general anaesthetic produced the hemodynamic combination that culminated in the cardiac arrest. Causation was therefore established.

The appellate analysis

The Court of Appeal applied the Housen v Nikolaisen, 2002 SCC 33, standard of review:

• Errors of law: correctness
• Findings of fact and mixed questions: palpable and overriding error
• Causation findings: typically reviewed for palpable and overriding error

The defendants’ appellate arguments focused on:

• The rejection of AFE was unsupported by the evidence
• The trial judge had not adequately explained the anaesthetic accident
• The causation analysis was inadequate

The Court of Appeal found no palpable and overriding error on any ground. The trial judge’s analysis was supported by the expert evidence at trial. The trial judge had explicitly identified the breaches, the causal mechanisms, and the chain from breach to harm. The rejection of AFE was supported by the clinical features (rarity, diagnosis-of-exclusion framework, absence of coagulopathy) and by the expert testimony from both sides.

The Court of Appeal cited Sacks v Ross, 2017 ONCA 773, for the proposition that the trier of fact’s primary task in causation analysis is to determine what likely happened on the evidence. The trial judge had performed this task appropriately by evaluating and ranking the competing causal theories.

The appeal was dismissed.

The causation-by-elimination framework

The doctrinal centerpiece of Hemmings is the causation-by-elimination framework that operates where defendants propose alternative non-negligent causes for the harm.

The framework, distilled:

Where the defendant proposes an alternative non-negligent cause:

• The plaintiff does not need to disprove every possible alternative — only to establish that the alleged negligent cause is more probable than the proposed alternative
• The trier of fact must compare the competing theories on the available evidence
• The framework is not “did the defendant cause the harm?” but “what likely happened?”
• The plaintiff prevails if the balance of probabilities favours the alleged negligent cause
• The defendant prevails if the balance favours the alternative or remains genuinely uncertain

Practical considerations for assessing competing causal theories:

• Prior probability (rarity) of each cause
• Clinical features that fit or do not fit each theory
• Temporal sequence (did each potential cause have the opportunity to operate when and how the harm manifested)
• Expert evidence on the likelihood of each cause
• Absence of features that would be expected with each cause (in AFE, the absence of coagulopathy)
• Identifiable alternative cause (where one exists, diagnoses of exclusion become harder to maintain)

The framework is broadly applicable in malpractice cases where alternative causal theories are at play. Obstetric emergencies are one common context (AFE, hemorrhage, embolism, eclampsia). Cardiac events during surgery are another (acute MI, pulmonary embolism, arrhythmia, anaesthetic complication). Sudden deteriorations during medical care often invite competing causal explanations. The Hemmings/Sacks v Ross framework applies across these contexts.

The AFE defence and its limits

Hemmings is doctrinally important as a leading Ontario case on the AFE defence in obstetric malpractice. The case clarifies the limits of the defence:

• AFE is extraordinarily rare; the prior probability is low
• AFE is a diagnosis of exclusion; where an identifiable alternative cause exists, AFE becomes less likely as the explanation
• The Clark criteria, particularly the coagulopathy/DIC requirement, structure the assessment
• The absence of coagulopathy is meaningful evidence against AFE
• The Clark criteria are not absolute (AFE without coagulopathy is recognized in the literature) but the absence is a factor

For plaintiff counsel facing the AFE defence, the practical analysis includes:

• Was coagulopathy or DIC present in this case?
• Was the onset consistent with AFE (sudden, severe) or more gradual (suggesting alternative)?
• Was there an identifiable alternative cause (anaesthetic event, hemorrhage, embolism, eclampsia)?
• Is the sequence of events consistent with AFE timing or with another mechanism?

Where the answers to these questions weigh against AFE, the defence faces substantial evidentiary challenges. Hemmings illustrates the analysis applied at trial and on appeal.

Difficult airway management and the standard of care

The case also engages the standard of care for difficult airway management in obstetric anaesthesia. The breaches identified at trial included failure to properly assess the airway and inadequate management of the difficult intubation when it occurred.

The standard of care for airway management includes:

Preoperative assessment. Before induction of general anaesthesia, the anaesthesiologist should perform a focused airway assessment. The Mallampati grading (visual examination of oropharyngeal structures), evaluation of thyromental distance, neck mobility, dentition, and previous anaesthetic history all inform the prediction of difficult intubation. Pregnancy increases the difficulty of airway management; the obstetric population requires particular attention.

Decision-making about general anaesthesia. Where regional anaesthesia is available and adequate, the standard preference is regional. Conversion to general should be based on specific clinical indication, not on general patient distress.

Equipment preparation. Where general anaesthesia is planned or anticipated as a possibility, appropriate airway equipment should be available — varied laryngoscope blades, video laryngoscopy, supraglottic airway devices, equipment for surgical airway access in extreme circumstances.

Response to failed intubation. The ASA difficult airway algorithm and the Difficult Airway Society guidelines provide structured frameworks for responding to failed intubation:

• Initial attempt
• Reposition or change technique
• Call for help
• Maintain oxygenation
• Consider awakening if possible
• Surgical airway as last resort

Documentation and team communication. Difficult intubation must be documented clearly so subsequent anaesthesia care providers are alerted.

The standard of care framework in Hemmings operates against this backdrop. The trial finding of breach on airway assessment and inappropriate conversion sits within the broader SOC for obstetric airway management.

Comparison with Williamson v Wang

The two anaesthesia cases in the rewritten cluster produce sharply different outcomes:

Williamson v Wang (BC, 2024 BCSC 1227, defendant win): Failed obstetric epidural with broken needle and retained fragment; alleged chronic back pain; outcome-based reasoning rejected; SOC and causation both defeated.

Hemmings v Peng (Ontario, 2024 ONCA 318, plaintiff win): Catastrophic anoxic brain injury during caesarean section; AFE defence rejected; multiple breaches identified (airway assessment + inappropriate conversion); $12 million affirmed.

The contrast illustrates several doctrinal points:

• Outcome severity matters at trial. Cases with catastrophic outcomes attract more careful judicial analysis (though they do not relax the SOC standard).
• The framework distinguishing accepted technique from negligent execution. Williamson engaged the iatrogenic-pain vs negligent-injury distinction. Hemmings engaged the causation-by-elimination framework between negligent and non-negligent causes. Both frameworks operate to distinguish what proper care would have produced from what negligent care actually produced.
• Multi-breach vs single-breach cases. Hemmings involved a conjunctive breach analysis (airway assessment + inappropriate conversion). Williamson involved single-breach allegations that failed on both SOC and causation.
• Different appellate postures. Williamson is a defendant trial win not appealed; Hemmings is a defendant appeal from a plaintiff trial win.

Together the two cases provide important balance to the cluster’s anaesthesia coverage and illustrate the range of doctrinal outcomes available in this practice area.

The appellate cluster — ten cases, three plaintiff affirmances

Hemmings v Peng is the tenth case in the rewritten appellate cluster and the third clean appellate affirmance of a plaintiff trial victory:

• Willick v Willard (Ont CA): defendant affirmance
• Hanson-Tasker v Ewart (BC CA): defendant affirmance
• Dumesnil v Jacob (Manitoba CA): new trial after defendant judgment
• Penate v Martoglio (Ont CA): new trial after defendant judgment
• Rybakov v Khattak (BC CA): defendant affirmance
• Focken v Miller (BC CA): defendant affirmance
• Henry v Zaitlen (Ont CA): affirmance of plaintiff jury verdict
• Denman v Radovanovic (Ont CA): affirmance of plaintiff bench-trial liability
• Rogerson v Grey Bruce (Ont CA): defendant affirmance; mandatory reporting + multi-step causation
• Hemmings v Peng (Ont CA): affirmance of plaintiff bench-trial; causation by elimination + AFE rejection

Seven defendant-favourable dispositions against three plaintiff affirmances. This is the most balanced plaintiff/defence representation in recent Canadian appellate malpractice jurisprudence and provides comprehensive doctrinal coverage across the major frameworks (expert evidence, causation, informed consent, jury procedure, mandatory reporting, anaesthesia).

The plaintiff wins sub-grouping — four cases

Hemmings v Peng is the fourth plaintiff win in the rewritten cluster:

• Kotorashvili v Lee (Ontario, trial): $35,000 — orthopaedic surgery; deviation from own treatment plan
• Henry v Zaitlen (Ontario, trial + appellate): ~$1.5 million — failure to investigate progressive neurological symptoms
• Denman v Radovanovic (Ontario, trial + appellate): $8.5 million — informed consent for multi-step AVM treatment
• Hemmings v Peng (Ontario, trial + appellate): $12 million — anaesthetic accident during caesarean section

The four cases span:

• Damages from $35,000 to $12 million
• Bench trials (Kotorashvili, Denman, Hemmings) and jury trials (Henry)
• Specialty areas (orthopaedics, neurology, interventional neuroradiology, obstetric anaesthesia)
• Theories of breach (treatment plan deviation, failure to investigate, informed consent, anaesthetic management)
• Causation frameworks (direct, temporal/delayed diagnosis, modified objective informed consent, causation by elimination)

The sub-grouping now provides substantial balance to the cluster’s many causation/SOC defeat cases and illustrates that the doctrinal framework supports plaintiff outcomes where the facts and the evidence align.

Doctrinal lessons

The case stands for several propositions.

Causation by elimination is the central framework when defendants propose alternative causes. The trier of fact must compare the competing theories on the available evidence and determine what likely happened. The plaintiff does not need to disprove every alternative; the plaintiff needs to establish that the alleged negligent cause is more probable than the proposed non-negligent alternative.

The AFE defence requires the clinical features to fit. Where coagulopathy is absent, where identifiable alternative causes exist, and where the timing or progression does not match AFE, the diagnosis-of-exclusion framework operates against the defence.

General anaesthesia is a last resort in caesarean section. Conversion from regional to general requires specific clinical indication, not simply patient agitation. Where the conversion was inappropriate and produced the cardiovascular and airway risks that culminated in cardiac arrest, the conversion itself is a breach.

Difficult airway management requires preoperative assessment. The standard of care includes focused airway evaluation before induction of general. Failure to perform that assessment, combined with inappropriate decisions about general anaesthesia, can produce a breach analysis that involves multiple distinct failures combining to produce harm.

Conjunctive breaches can support causation. Where multiple breaches operate together to produce harm, the causation analysis under Clements v Clements asks whether, absent the breaches, the harm would have occurred. Where the answer is no, causation is established even if no single breach in isolation would have caused the harm.

Appellate review of plaintiff verdicts is substantially deferential. The Housen v Nikolaisen framework applies to plaintiff verdicts as to defendant verdicts. Where the trial judge’s analysis is supported by the expert evidence and shows no palpable and overriding error, the verdict will stand.

Multi-million-dollar verdicts for catastrophic maternal injury are sustainable. $12 million for catastrophic anoxic brain injury in a young mother sets a reference point. Together with Denman ($8.5M) and Rogerson ($13M+), the cluster now has substantial damages calibration data for catastrophic-injury malpractice claims.

Why this case matters

For prospective clients considering obstetric malpractice claims. The case illustrates the realistic possibility of plaintiff success in complex obstetric anaesthesia cases — even in the face of an AFE defence. Where the clinical features do not fit AFE (no coagulopathy, identifiable alternative cause, inconsistent timing), and where the alternative causal theory is supported by expert evidence on the standard of care, plaintiff outcomes are realistic. For more on the realistic evaluation of malpractice claims, see Suing for Medical Malpractice in Ontario: What You Need to Know and the Birth Injury Lawyer in Toronto page for related obstetric malpractice topics.

For plaintiff counsel. The case provides several important precedents:

• The causation-by-elimination framework operates to support plaintiff causation where the alternative non-negligent cause is unsupported by the clinical features
• AFE defence challenges should explicitly engage the Clark criteria and the absence of coagulopathy
• Difficult airway management cases can support conjunctive breach analysis (assessment + decision + execution)
• Sacks v Ross “what likely happened” framework is the operative appellate standard for causation
• Plaintiff verdicts of $12 million for catastrophic maternal brain injury are sustainable on appeal where the underlying analysis is sound

For defence counsel. The AFE defence remains available but requires the clinical features to fit. Where the patient lacks coagulopathy, where identifiable alternative causes are present, and where the timing or progression of the collapse does not match AFE, the defence faces substantial challenges. Counsel evaluating the AFE defence should engage clinical experts familiar with the Clark criteria and the broader diagnostic framework.

For practising anaesthesiologists, particularly those in obstetric practice. The case is a substantial professional reminder. The operational lessons:

• Preoperative airway assessment is part of the standard of care; document findings and inform subsequent clinical decisions
• Conversion from regional to general in caesarean section requires specific clinical indication; patient agitation alone is generally insufficient
• Where conversion is undertaken, anticipate the combined hemodynamic effects of spinal plus general and prepare accordingly
• Difficult intubation requires a structured response framework (ASA difficult airway algorithm, DAS guidelines); call for help early
• Documentation of clinical reasoning is essential

For more on related obstetric and anaesthesia malpractice, see Williamson v Wang for the contrasting BC anaesthesia case, and the Birth Injury Lawyer page for related practice area information.

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Decision Date: April 30, 2024

Jurisdiction: Court of Appeal for Ontario

Citation: Hemmings v Peng, 2024 ONCA 318 (CanLII)

Outcome: Plaintiff trial judgment of $12 million affirmed. Appeal dismissed.

Key authorities: Clements v Clements, 2012 SCC 32 (but-for causation framework); Sacks v Ross, 2017 ONCA 773 (the trier of fact’s task is to determine what likely happened); Housen v Nikolaisen, 2002 SCC 33 (appellate standard of review); ter Neuzen v Korn, [1995] 3 SCR 674 (expert evidence framework); Athey v Leonati, [1996] 3 SCR 458 (multiple cause framework)