In medical malpractice cases, the plaintiff must prove causation on a balance of probabilities. Where the defendant’s negligence creates the very causal uncertainty that makes the question difficult to answer, the law allows a trial judge to draw an inference of causation against the defendant. The leading case is Snell v Farrell, [1990] 2 SCR 311, reaffirmed and clarified in Benhaim v St-Germain, 2016 SCC 48. The inference is not automatic. It is discretionary. The trial judge weighs all the evidence and decides whether the inference is appropriate on the facts.
Hanson-Tasker v Ewart, 2023 BCCA 463, is the leading recent illustration of what happens when a defendant has marshaled substantial competing expert evidence and the trial judge declines to draw the Snell inference. The case involves a pre-term newborn who suffered permanent brain damage from kernicterus. The trial judge found the family physicians had breached the standard of care by failing to monitor her bilirubin levels in the days after discharge from hospital. The same trial judge found that the breach did not cause the brain injury. The British Columbia Court of Appeal affirmed.
The case is doctrinally important for three reasons. It is a clear application of the Snell/Benhaim framework in a complex medical case. It shows the discretionary limits of the adverse inference. And it confirms the deferential standard of appellate review applicable to the trial judge’s discretionary causation analysis.
The clinical context: newborn jaundice and kernicterus
Most healthy newborns develop some degree of jaundice in the first week of life. The mechanism is straightforward: babies have an elevated rate of red blood cell turnover and immature livers that have not yet developed the full capacity to process bilirubin (the yellow pigment produced when red blood cells break down). Bilirubin accumulates in the bloodstream and becomes visible in the skin and eyes. This physiologic jaundice affects approximately half of term babies and is somewhat more common in pre-term newborns. It typically peaks and resolves within the first week or two.
In rare cases, bilirubin levels rise high enough to cross the blood-brain barrier and damage the developing brain. This is called acute bilirubin encephalopathy. The symptoms include lethargy, refusal to feed, high-pitched crying, severe back arching, seizures, and apnea. If the bilirubin neurotoxicity is not promptly reversed, the brain damage can become permanent — a condition called kernicterus. Kernicterus produces lifelong cognitive and motor impairment.
The standard of care for newborn jaundice involves clinical assessment, bilirubin testing where appropriate, and follow-up monitoring of at-risk infants. Pre-term babies are at higher risk. So are babies who appear visibly jaundiced shortly after birth. The first-line treatment for hyperbilirubinemia is phototherapy. In more severe cases, exchange transfusion is required.
The substantive case
Kyrcee Hanson-Tasker was born slightly pre-term on July 29, 1996. She was discharged from hospital two days later. Her bilirubin was measured before discharge and was not at a level requiring phototherapy.
She was seen by Dr. Brian Ewart, a family physician, on August 1 — the day after discharge and three days after birth. Dr. Ewart noted Kyrcee was “icteric” (jaundiced). No follow-up appointment was scheduled to monitor her condition. No follow-up bilirubin test was ordered.
The trial judge found that, given Kyrcee’s elevated risk profile for hyperbilirubinemia (pre-term birth) and her evident jaundice on examination at approximately 38 hours of life, the family physicians had breached the standard of care by failing to monitor her in the days following discharge to assess the need for a follow-up bilirubin test.
Kyrcee’s bilirubin was not tested again until her re-admission to hospital on August 6, when she was in distress and displaying classic symptoms of acute bilirubin encephalopathy. Her bilirubin was severely elevated. She developed kernicterus. Despite prompt medical intervention on re-admission, the brain damage could neither be avoided nor reversed.
The two competing causation theories
Because Kyrcee was not tested between August 1 and August 5, her bilirubin levels during those days were unknown. The etiology of her severe hyperbilirubinemia could not be definitively determined. The causation issue at trial was therefore framed as a contest between two competing expert theories about what had happened during the unobserved period.
The plaintiff’s theory (Dr. Kaplan). The plaintiff’s expert posited a pathologically abnormal, progressive, and essentially linear increase in bilirubin levels from birth to re-admission. On this theory, the bilirubin rise was the same underlying process throughout the eight days. Had the family physicians ordered follow-up testing as the standard of care required, the rising bilirubin would have been caught, treatment (phototherapy or exchange transfusion) would have been instituted, and the kernicterus would have been prevented.
The defence theory (Drs. Boulton and Van Aerde). The defence experts posited a “biphasic” trajectory. On their view, the bilirubin rise in the first several days was a normal physiological process that peaked and plateaued. Then, approximately 24 hours before re-admission, a massive and unpredictable “acute oxidative hemolytic event” occurred. The hemolytic event caused rapid red blood cell destruction, acute anemia, and severely elevated bilirubin levels. On this theory, even if follow-up testing had been done on August 1, the bilirubin would have been within an acceptable range; the catastrophic rise occurred only in the final 24 hours and was unrelated to the family physicians’ failure to monitor.
The trial judge accepted the defence theory. The reasoning rested on two key considerations:
- The absence of symptoms before August 6. On the plaintiff’s linear theory, Kyrcee would have been displaying the prodrome of toxic hyperbilirubinemia (lethargy, feeding refusal, high-pitched crying, abnormal tone) well before August 6. Apart from increasing jaundice, no such symptoms were reported until that morning. The trial judge described this as “a glaring hole in the theory of the plaintiff’s case.”
- The hemoglobin evidence. The trial judge accepted the defence experts’ evidence that the sharp drop in Kyrcee’s hemoglobin between 11:15 a.m. and 8:54 p.m. on August 6 was objective evidence of an acute hemolytic event, which could not have occurred over the more prolonged period posited by the plaintiff’s linear progression theory.
On the trial judge’s analysis, the cause of Kyrcee’s brain injury was an acute oxidative hemolytic event of independent origin, not a progressive rise in bilirubin that monitoring would have caught. Even with follow-up testing on August 1, the outcome would have been the same.
The appeal
The plaintiff appealed on two grounds.
Ground 1: failure to apply the Snell adverse inference. The plaintiff argued that the trial judge erred in failing to consider whether to draw an inference of causation against the defendants in circumstances where the causal uncertainty (the unknown bilirubin levels between August 1 and August 5) was itself attributable to the defendants’ negligence. The defendants’ breach (failure to order follow-up testing) had produced the very information gap that made causation difficult to prove.
Ground 2: misapprehension of evidence. The plaintiff argued that the trial judge had misapprehended material evidence, including the evidence of Kyrcee’s worsening jaundice in the days before re-admission, the distinction between hyperbilirubinemia (the condition requiring treatment) and kernicterus (the resulting injury), and the expert evidence on bilirubin trajectory and detectable hemolysis.
The Snell/Benhaim framework
The doctrinal foundation of the first ground of appeal is the framework articulated in Snell v Farrell and reaffirmed in Benhaim v St-Germain.
In Snell, the Supreme Court of Canada addressed the difficulty plaintiffs face in proving causation where the science is uncertain and the defendant’s negligence has obscured what would have happened with appropriate care. The Court held that a trial judge may, in appropriate circumstances, draw an inference of causation against a defendant whose negligence has produced the causal uncertainty. The inference is part of a “robust and pragmatic” approach to common-sense reasoning about evidence. It is not mandatory. It can be displaced where the defendant adduces evidence that contradicts the inference.
In Benhaim, the Court reaffirmed and clarified Snell. The Court held that the trial judge’s decision to draw or not draw the inference is a discretionary call reviewed deferentially. The trial judge does not commit a legal error by failing to expressly mention Snell where the framework was implicitly engaged. The presence of substantial expert evidence on causation can displace the inference.
The framework has three operative features. First, the inference is available where the defendant’s negligence creates causal uncertainty. Second, the inference is discretionary, not mandatory. Third, the inference can be displaced where the defendant marshals substantial competing evidence.
The Court of Appeal’s analysis
The Court of Appeal rejected both grounds.
On the Snell ground, the Court held that the trial judge was aware of the availability of the adverse inference and had implicitly exercised his discretion not to draw it on the facts. The case was distinguishable from earlier BC authority (the Court referenced Ghiassi and similar cases) precisely because of the “substantial body of expert evidence called by both parties on the issue of causation.” Where competing expert evidence allows the trial judge to make positive factual findings about what occurred (here, that the brain injury was caused by an independent acute hemolytic event), the Snell inference is not the operative framework.
On the misapprehension ground, the Court of Appeal rejected the argument that the trial judge had ignored the evidence of worsening jaundice. The trial judge had considered jaundice but had placed significant weight on the absence of other symptoms that would have been expected on the plaintiff’s linear theory. He was entitled to assess the totality of the expected symptoms rather than treating progressive jaundice as dispositive. That assessment was within his discretion as the trier of fact.
The appeal was dismissed.
The doctrinal lessons
The case stands for several propositions.
Snell is not automatic. A plaintiff who has shown standard-of-care breach and some evidence of causation is not entitled to a Snell inference as of right. The inference is discretionary, and the trial judge weighs all the evidence — including the defendant’s contrary expert evidence — in deciding whether to draw it.
Substantial competing expert evidence displaces the inference. Where the defendant marshals substantial expert evidence proposing an alternative theory of causation, and the trial judge accepts that evidence, the Snell inference will generally not apply. The inference is most likely to operate in cases where the defendant has not addressed the causation question or where the defendant’s evidence is weak.
The trial judge’s discretion is reviewed deferentially. The decision to draw or not draw the Snell inference is reviewed on a deferential standard. The appellate court will not substitute its judgment for that of the trial judge on what is essentially a factual exercise.
Implicit reasoning is sufficient. The trial judge does not have to expressly cite Snell or expressly explain why the inference is not being drawn. Where the analysis demonstrates that the trial judge engaged with the causation question and accepted positive findings displacing the inference, the absence of an explicit Snell discussion is not error.
Causation in birth injury cases often turns on the natural history of the disease. The defence theory in Hanson-Tasker turned on the natural history of bilirubin metabolism in the newborn — specifically, the difference between physiologic hyperbilirubinemia and an acute hemolytic event. In any birth injury causation case, the natural history of the underlying condition is the foundation of the analysis. Plaintiff counsel and defence counsel need experts who can speak to the natural history persuasively.
Parallels with other cluster cases
Hanson-Tasker fits within the broader pattern of cases where the plaintiff proves a breach of the standard of care but loses on causation. The closest parallels in the rewritten case-comment cluster are:
Knight v Lawson (Notable Case). A case I tried at the Ontario Superior Court of Justice. The standard of care was breached in the management of a ureteric injury during gynecologic surgery, but causation could not be established. The doctrinal point is the same as Hanson-Tasker: breach alone is not enough; the breach must be shown to have caused the harm.
Tripp v Ross (Manitoba). A case where the colonoscopy negligence was admitted but the cancer was already metastatic at the relevant time. The causation defeat operated on the natural history of the underlying disease, not on a Snell analysis.
Willick v Willard (Court of Appeal for Ontario). A delayed splenic rupture case affirmed on appeal. The COA upheld the trial judge’s factual findings on standard of care, noting the deferential standard of review.
The four cases together — Hanson-Tasker, Knight, Tripp, Willick — illustrate the realistic distribution of outcomes when causation is the contested issue in malpractice litigation. Hanson-Tasker adds the Snell dimension; Tripp adds the natural history dimension; Knight and Willick add the deferential standard of review dimension.
The birth injury cluster
Hanson-Tasker is the sixth case in the rewritten birth injury sub-cluster:
- Woods v Jackiewicz: a Notable Case I conducted producing an $11.5 million jury verdict in a cerebral palsy case
- KY v Bahler: failure to refer a high-risk twin pregnancy
- Rathan v Scheufler: brachial plexus injury caused by excessive force in delivery
- Gilmore v Love: a BC birth injury case involving newborn skull fractures and real-time informed consent during labour
- Lal v Anderson: a BC procedural decision on a jury motion in a complex birth injury case
- Hanson-Tasker v Ewart (this case): a BC appellate decision on causation in a kernicterus case
The cluster now spans substantive birth injury, procedural birth injury, and causation birth injury. The four substantive cases (Woods, KY v Bahler, Rathan, Gilmore) demonstrate the substantive standard-of-care framework. Lal v Anderson and Hanson-Tasker add the procedural and causation dimensions.
The BC sub-cluster
Hanson-Tasker is the fifth BC case in the cross-province sub-cluster:
The BC cases are cross-province material that applies to Ontario practice because the underlying legal frameworks are substantively similar. Hanson-Tasker is particularly portable because the Snell framework is national.
Why this case matters
For plaintiff counsel. Snell is not a shortcut. Where the defence has the resources to call substantial competing expert evidence (as the CMPA-defended cases generally do), the plaintiff cannot rely on the adverse inference to fill causation gaps. The case must be built on expert evidence that affirmatively proves causation, not on a procedural inference. Hanson-Tasker is a useful reminder of where the Snell doctrine actually operates: in cases where the defence has not effectively addressed the causation question. In well-defended cases, Snell is rarely the decisive feature.
For defence counsel. The case is a useful precedent on the limits of Snell. A defence that marshals substantial expert evidence — proposing a specific alternative theory of causation, accounting for the available clinical evidence, and giving the trial judge a viable factual finding to make — generally displaces the adverse inference. The investment in expert evidence is the foundation of this defence.
For prospective clients in birth injury cases. Newborn brain injury cases are among the most complex in malpractice litigation. They typically involve multiple potential causes (intrapartum events, perinatal events, post-natal events, congenital conditions) and require expert evidence from neonatology, pediatric neurology, obstetrics, and sometimes other specialties. A finding of standard-of-care breach does not produce automatic recovery. The medicine has to show that the breach caused the injury. Where the cause was an unrelated event that the negligence did not affect, recovery may not be available.
For more on birth injury malpractice in Ontario, see Birth Injury Lawyer in Toronto. For the broader framework of malpractice claims in Ontario, see Suing for Medical Malpractice in Ontario: What You Need to Know.
Decision Date: December 8, 2023
Jurisdiction: Court of Appeal for British Columbia
Citation: Hanson-Tasker v Ewart, 2023 BCCA 463 (CanLII)
Key authorities: Snell v Farrell, [1990] 2 SCR 311; Benhaim v St-Germain, 2016 SCC 48
Hanson-Tasker v Ewart: The Limits of the Snell Adverse Inference
A pre-term newborn with kernicterus lost her causation case despite a finding that her family physicians had breached the standard of care. The Snell adverse inference did not save the claim.
In medical malpractice cases, the plaintiff must prove causation on a balance of probabilities. Where the defendant’s negligence creates the very causal uncertainty that makes the question difficult to answer, the law allows a trial judge to draw an inference of causation against the defendant. The leading case is Snell v Farrell, [1990] 2 SCR 311, reaffirmed and clarified in Benhaim v St-Germain, 2016 SCC 48. The inference is not automatic. It is discretionary. The trial judge weighs all the evidence and decides whether the inference is appropriate on the facts.
Hanson-Tasker v Ewart, 2023 BCCA 463, is the leading recent illustration of what happens when a defendant has marshaled substantial competing expert evidence and the trial judge declines to draw the Snell inference. The case involves a pre-term newborn who suffered permanent brain damage from kernicterus. The trial judge found the family physicians had breached the standard of care by failing to monitor her bilirubin levels in the days after discharge from hospital. The same trial judge found that the breach did not cause the brain injury. The British Columbia Court of Appeal affirmed.
The case is doctrinally important for three reasons. It is a clear application of the Snell/Benhaim framework in a complex medical case. It shows the discretionary limits of the adverse inference. And it confirms the deferential standard of appellate review applicable to the trial judge’s discretionary causation analysis.
The clinical context: newborn jaundice and kernicterus
Most healthy newborns develop some degree of jaundice in the first week of life. The mechanism is straightforward: babies have an elevated rate of red blood cell turnover and immature livers that have not yet developed the full capacity to process bilirubin (the yellow pigment produced when red blood cells break down). Bilirubin accumulates in the bloodstream and becomes visible in the skin and eyes. This physiologic jaundice affects approximately half of term babies and is somewhat more common in pre-term newborns. It typically peaks and resolves within the first week or two.
In rare cases, bilirubin levels rise high enough to cross the blood-brain barrier and damage the developing brain. This is called acute bilirubin encephalopathy. The symptoms include lethargy, refusal to feed, high-pitched crying, severe back arching, seizures, and apnea. If the bilirubin neurotoxicity is not promptly reversed, the brain damage can become permanent — a condition called kernicterus. Kernicterus produces lifelong cognitive and motor impairment.
The standard of care for newborn jaundice involves clinical assessment, bilirubin testing where appropriate, and follow-up monitoring of at-risk infants. Pre-term babies are at higher risk. So are babies who appear visibly jaundiced shortly after birth. The first-line treatment for hyperbilirubinemia is phototherapy. In more severe cases, exchange transfusion is required.
The substantive case
Kyrcee Hanson-Tasker was born slightly pre-term on July 29, 1996. She was discharged from hospital two days later. Her bilirubin was measured before discharge and was not at a level requiring phototherapy.
She was seen by Dr. Brian Ewart, a family physician, on August 1 — the day after discharge and three days after birth. Dr. Ewart noted Kyrcee was “icteric” (jaundiced). No follow-up appointment was scheduled to monitor her condition. No follow-up bilirubin test was ordered.
The trial judge found that, given Kyrcee’s elevated risk profile for hyperbilirubinemia (pre-term birth) and her evident jaundice on examination at approximately 38 hours of life, the family physicians had breached the standard of care by failing to monitor her in the days following discharge to assess the need for a follow-up bilirubin test.
Kyrcee’s bilirubin was not tested again until her re-admission to hospital on August 6, when she was in distress and displaying classic symptoms of acute bilirubin encephalopathy. Her bilirubin was severely elevated. She developed kernicterus. Despite prompt medical intervention on re-admission, the brain damage could neither be avoided nor reversed.
The two competing causation theories
Because Kyrcee was not tested between August 1 and August 5, her bilirubin levels during those days were unknown. The etiology of her severe hyperbilirubinemia could not be definitively determined. The causation issue at trial was therefore framed as a contest between two competing expert theories about what had happened during the unobserved period.
The plaintiff’s theory (Dr. Kaplan). The plaintiff’s expert posited a pathologically abnormal, progressive, and essentially linear increase in bilirubin levels from birth to re-admission. On this theory, the bilirubin rise was the same underlying process throughout the eight days. Had the family physicians ordered follow-up testing as the standard of care required, the rising bilirubin would have been caught, treatment (phototherapy or exchange transfusion) would have been instituted, and the kernicterus would have been prevented.
The defence theory (Drs. Boulton and Van Aerde). The defence experts posited a “biphasic” trajectory. On their view, the bilirubin rise in the first several days was a normal physiological process that peaked and plateaued. Then, approximately 24 hours before re-admission, a massive and unpredictable “acute oxidative hemolytic event” occurred. The hemolytic event caused rapid red blood cell destruction, acute anemia, and severely elevated bilirubin levels. On this theory, even if follow-up testing had been done on August 1, the bilirubin would have been within an acceptable range; the catastrophic rise occurred only in the final 24 hours and was unrelated to the family physicians’ failure to monitor.
The trial judge accepted the defence theory. The reasoning rested on two key considerations:
On the trial judge’s analysis, the cause of Kyrcee’s brain injury was an acute oxidative hemolytic event of independent origin, not a progressive rise in bilirubin that monitoring would have caught. Even with follow-up testing on August 1, the outcome would have been the same.
The appeal
The plaintiff appealed on two grounds.
Ground 1: failure to apply the Snell adverse inference. The plaintiff argued that the trial judge erred in failing to consider whether to draw an inference of causation against the defendants in circumstances where the causal uncertainty (the unknown bilirubin levels between August 1 and August 5) was itself attributable to the defendants’ negligence. The defendants’ breach (failure to order follow-up testing) had produced the very information gap that made causation difficult to prove.
Ground 2: misapprehension of evidence. The plaintiff argued that the trial judge had misapprehended material evidence, including the evidence of Kyrcee’s worsening jaundice in the days before re-admission, the distinction between hyperbilirubinemia (the condition requiring treatment) and kernicterus (the resulting injury), and the expert evidence on bilirubin trajectory and detectable hemolysis.
The Snell/Benhaim framework
The doctrinal foundation of the first ground of appeal is the framework articulated in Snell v Farrell and reaffirmed in Benhaim v St-Germain.
In Snell, the Supreme Court of Canada addressed the difficulty plaintiffs face in proving causation where the science is uncertain and the defendant’s negligence has obscured what would have happened with appropriate care. The Court held that a trial judge may, in appropriate circumstances, draw an inference of causation against a defendant whose negligence has produced the causal uncertainty. The inference is part of a “robust and pragmatic” approach to common-sense reasoning about evidence. It is not mandatory. It can be displaced where the defendant adduces evidence that contradicts the inference.
In Benhaim, the Court reaffirmed and clarified Snell. The Court held that the trial judge’s decision to draw or not draw the inference is a discretionary call reviewed deferentially. The trial judge does not commit a legal error by failing to expressly mention Snell where the framework was implicitly engaged. The presence of substantial expert evidence on causation can displace the inference.
The framework has three operative features. First, the inference is available where the defendant’s negligence creates causal uncertainty. Second, the inference is discretionary, not mandatory. Third, the inference can be displaced where the defendant marshals substantial competing evidence.
The Court of Appeal’s analysis
The Court of Appeal rejected both grounds.
On the Snell ground, the Court held that the trial judge was aware of the availability of the adverse inference and had implicitly exercised his discretion not to draw it on the facts. The case was distinguishable from earlier BC authority (the Court referenced Ghiassi and similar cases) precisely because of the “substantial body of expert evidence called by both parties on the issue of causation.” Where competing expert evidence allows the trial judge to make positive factual findings about what occurred (here, that the brain injury was caused by an independent acute hemolytic event), the Snell inference is not the operative framework.
On the misapprehension ground, the Court of Appeal rejected the argument that the trial judge had ignored the evidence of worsening jaundice. The trial judge had considered jaundice but had placed significant weight on the absence of other symptoms that would have been expected on the plaintiff’s linear theory. He was entitled to assess the totality of the expected symptoms rather than treating progressive jaundice as dispositive. That assessment was within his discretion as the trier of fact.
The appeal was dismissed.
The doctrinal lessons
The case stands for several propositions.
Snell is not automatic. A plaintiff who has shown standard-of-care breach and some evidence of causation is not entitled to a Snell inference as of right. The inference is discretionary, and the trial judge weighs all the evidence — including the defendant’s contrary expert evidence — in deciding whether to draw it.
Substantial competing expert evidence displaces the inference. Where the defendant marshals substantial expert evidence proposing an alternative theory of causation, and the trial judge accepts that evidence, the Snell inference will generally not apply. The inference is most likely to operate in cases where the defendant has not addressed the causation question or where the defendant’s evidence is weak.
The trial judge’s discretion is reviewed deferentially. The decision to draw or not draw the Snell inference is reviewed on a deferential standard. The appellate court will not substitute its judgment for that of the trial judge on what is essentially a factual exercise.
Implicit reasoning is sufficient. The trial judge does not have to expressly cite Snell or expressly explain why the inference is not being drawn. Where the analysis demonstrates that the trial judge engaged with the causation question and accepted positive findings displacing the inference, the absence of an explicit Snell discussion is not error.
Causation in birth injury cases often turns on the natural history of the disease. The defence theory in Hanson-Tasker turned on the natural history of bilirubin metabolism in the newborn — specifically, the difference between physiologic hyperbilirubinemia and an acute hemolytic event. In any birth injury causation case, the natural history of the underlying condition is the foundation of the analysis. Plaintiff counsel and defence counsel need experts who can speak to the natural history persuasively.
Parallels with other cluster cases
Hanson-Tasker fits within the broader pattern of cases where the plaintiff proves a breach of the standard of care but loses on causation. The closest parallels in the rewritten case-comment cluster are:
Knight v Lawson (Notable Case). A case I tried at the Ontario Superior Court of Justice. The standard of care was breached in the management of a ureteric injury during gynecologic surgery, but causation could not be established. The doctrinal point is the same as Hanson-Tasker: breach alone is not enough; the breach must be shown to have caused the harm.
Tripp v Ross (Manitoba). A case where the colonoscopy negligence was admitted but the cancer was already metastatic at the relevant time. The causation defeat operated on the natural history of the underlying disease, not on a Snell analysis.
Willick v Willard (Court of Appeal for Ontario). A delayed splenic rupture case affirmed on appeal. The COA upheld the trial judge’s factual findings on standard of care, noting the deferential standard of review.
The four cases together — Hanson-Tasker, Knight, Tripp, Willick — illustrate the realistic distribution of outcomes when causation is the contested issue in malpractice litigation. Hanson-Tasker adds the Snell dimension; Tripp adds the natural history dimension; Knight and Willick add the deferential standard of review dimension.
The birth injury cluster
Hanson-Tasker is the sixth case in the rewritten birth injury sub-cluster:
The cluster now spans substantive birth injury, procedural birth injury, and causation birth injury. The four substantive cases (Woods, KY v Bahler, Rathan, Gilmore) demonstrate the substantive standard-of-care framework. Lal v Anderson and Hanson-Tasker add the procedural and causation dimensions.
The BC sub-cluster
Hanson-Tasker is the fifth BC case in the cross-province sub-cluster:
The BC cases are cross-province material that applies to Ontario practice because the underlying legal frameworks are substantively similar. Hanson-Tasker is particularly portable because the Snell framework is national.
Why this case matters
For plaintiff counsel. Snell is not a shortcut. Where the defence has the resources to call substantial competing expert evidence (as the CMPA-defended cases generally do), the plaintiff cannot rely on the adverse inference to fill causation gaps. The case must be built on expert evidence that affirmatively proves causation, not on a procedural inference. Hanson-Tasker is a useful reminder of where the Snell doctrine actually operates: in cases where the defence has not effectively addressed the causation question. In well-defended cases, Snell is rarely the decisive feature.
For defence counsel. The case is a useful precedent on the limits of Snell. A defence that marshals substantial expert evidence — proposing a specific alternative theory of causation, accounting for the available clinical evidence, and giving the trial judge a viable factual finding to make — generally displaces the adverse inference. The investment in expert evidence is the foundation of this defence.
For prospective clients in birth injury cases. Newborn brain injury cases are among the most complex in malpractice litigation. They typically involve multiple potential causes (intrapartum events, perinatal events, post-natal events, congenital conditions) and require expert evidence from neonatology, pediatric neurology, obstetrics, and sometimes other specialties. A finding of standard-of-care breach does not produce automatic recovery. The medicine has to show that the breach caused the injury. Where the cause was an unrelated event that the negligence did not affect, recovery may not be available.
For more on birth injury malpractice in Ontario, see Birth Injury Lawyer in Toronto. For the broader framework of malpractice claims in Ontario, see Suing for Medical Malpractice in Ontario: What You Need to Know.
Decision Date: December 8, 2023
Jurisdiction: Court of Appeal for British Columbia
Citation: Hanson-Tasker v Ewart, 2023 BCCA 463 (CanLII)
Key authorities: Snell v Farrell, [1990] 2 SCR 311; Benhaim v St-Germain, 2016 SCC 48
Paul Cahill
Partner, Davidson Cahill Morrison LLP | LSO Certified Specialist in Civil Litigation
Paul represents victims of medical malpractice across Ontario, with trial experience including a $11.5M jury verdict in a birth injury case. He is recognized in Best Lawyers in Canada and serves as trial counsel to other lawyers on complex medical negligence matters.
About PaulMore on medical malpractice in Ontario.
Other articles by Paul exploring the conditions, decisions, and systems behind preventable medical harm.
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