The Legal Principles
The law on causation is clear and usually not in dispute. The plaintiff must prove, on the balance of probabilities, the defendant’s act (or failure to act) caused the injury. The generally applicable test is the “but for” test; the plaintiff must “show that the injury would not have occurred but for the negligence of the defendant.”2
The plaintiff is required to lead sufficient evidence to establish, using a robust and pragmatic approach to the assessment, that the defendant’s negligence was the cause, both in fact and in law, of the injuries sustained.3 The plaintiff must establish that the defendant’s negligence was necessary to bring about the injury (the injury would not have occurred without this negligence).4
The defendant’s wrong need not be the sole cause of the loss, but it must be part of the cause. “But for” causation raises the counterfactual question: what would likely have happened if the defendant had discharged his or her duty? Properly understood, “but for” causation simply means causation in fact.5
One of the issues that often arises with clients seeking to pursue a medical malpractice claim is the possibility of a better outcome. If, for example, expectant management (a ‘wait and see’ approach) led a child to sustain birth injuries and the experts agree the patient should have been actively treated, any parent will tell you they wanted the active treatment, no matter the risks. If the active treatment only offered a 25% chance of avoiding or improving the outcome, they cannot succeed in a medical malpractice claim, a concept that can be difficult to comprehend on an emotional level. The law is summarized by Adair J. in Wiebe:6
- [115] It is not enough for a plaintiff to establish that a medical outcome might have been better had the defendant(s) acted differently. The trier of fact must be convinced by the evidence that the outcome probably would have been more favourable in order to be satisfied of causation on a balance of probabilities. See Seatle et al. v. Purvis et al., 2005 BCSC 1567, at para. 145, aff’d 2007 BCCA 349.
- [116] Moreover, as Beames J. observed in Jackson v. Kelowna General Hospital et al., 2006 BCSC 279, at para. 33, aff’d 2007 BCCA 129:
- [33] The plaintiff cannot meet the onus upon him to prove causation by merely proving the loss of a chance (Cottrelle, supra, at para. 36). Similarly, it is not enough for a plaintiff to prove that the defendants “created a risk scenario within which the plaintiff’s pain, suffering and losses [have] occurred” (Oliver (Public Trustee of) v. Ellison, [1998] B.C.J. No. 589 (S.C.), at paras. 31-33; St-Jean v. Mercier, 2002 SCC 15, [2002] 1 S.C.R. 491 at para. 116).
Examples in the Caselaw
K.S. (Litigation Representative of) v. Willox, is a prime example of the loss of chance being insufficient to ground a claim, despite a known treatment that may have drastically altered the child’s outcome and avoided a catastrophic injury.7 In K.S., the plaintiff was a 15-year-old boy with severe cognitive deficits, limited vision in one eye, hypersensitivity to external stimuli and severe Autism Spectrum Disorder. The lawsuit revolved around the care K.S.’s mother, J.S., received during her pregnancy. J.S. was pregnant for the first time and cared for by Dr. Willox during her pregnancy. She advised him that her own mother had an incompetent cervix, had miscarried at least once and had received cervical cerclage for her pregnancies with J.S. and her siblings. Dr. Willox told J.S. that an incompetent cervix was not genetic. During her pregnancy, J.S. attended hospital and Dr. Willox’s office for a few concerns, including passing a clot, vaginal discharge and spotting.
