Causation in Medical Malpractice Cases: A Quarter-Century Review

Ediger v. Johnston (2013)

The SCC decision in Ediger v Johnston²⁸ provides further clarification to medical malpractice plaintiffs, overturning the BCCA decision that relied on the line of authority in Moore. In this birth injury case, the defendant obstetrician attempted to deliver the infant plaintiff using mid-level forceps but failed to inform the mother of the risks of the procedure, and failed to ensure that immediate surgical backup was available in the event that the forceps delivery failed and an emergency c-section was necessary. Ultimately, the forceps attempt failed, and the infant plaintiff was later delivered by emergency c-section. She had suffered an asphyxial event and was diagnosed with spastic quadriplegia and cerebral palsy. The trial judge found that the defendant breached the standard of care and caused the plaintiff’s injuries.

The BCCA overturned the trial decision, finding that the plaintiff could not prove that the defendant actually caused the injury and that the trial judge improperly relied on Snell in order to draw an inference of causation. The SCC reinstated the trial judgement, finding that the trial judge properly followed the approach in Snell. The trier of fact, upon weighing the evidence, may indeed draw an inference of causation if the defendant does not introduce sufficient evidence contrary to the plaintiff’s theory of causation in order to defend their actions.²⁹ In determining whether the defendant has introduced sufficient evidence, the trier of fact should take into account the relative position of each party to adduce evidence.

Conclusion

Today, the governing test for causation is well established as the “but for” test.³⁰ Causation is determined on a balance of probabilities, taking into account and weighing all of the relevant evidence. Causation does not need to be proven with scientific precision, and the courts are expected to adopt a robust and pragmatic approach to the facts with the ability to draw inferences of causation using common sense. Where a claim involves a complex causation analysis, counsel will benefit from a firm understanding of the evolution of the law to prevent opposing counsel from relying on an improper line of reasoning.

1. Snell v. Farrell, 1990 CanLII 70 (SCC), [1990] 2 SCR 311 [ [Snell].
2. McGhee v. National Coal Board, [1973] 1 W.L.R. 1.
3. Snell, supra note 1 at 322.
4. Snell, supra note 1 at 328.
5. Snell, supra note 1 at 328-330.
6. Snell, supra note 1 at 331.
7. Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 SCR 458 [Athey].
8. Ibid at para 41.
9. Ibid at para 17.
10. Snell, supra note 1 at 330-331; Athey, supra note 7 at para 16.
11. Moore v. Castlegar & District Hospital, 1998 CanLII 4906 (BC CA) [Moore].
12. Ibid at para 9.
13. Ibid at para 11.
14. Resurfice Corp. v. Hanke, 2007 SCC 7 (CanLII), [2007]) 1 SCR 333 [Resurfice].
15. Ibid at para 17.
16. Ibid at para 3.
17. Ibid at para 4.
18. Ibid at para 21.
19. Ibid at para 23.
20. Ibid at paras 24-25.
21. Clements v. Clements, 2012 SCC 32 (CanLII), [2012] 2 SCR 181 [Clements].
22. Ediger v. Johnston, 2011 BCCA 253.
23. Clements, supra note 21 at para 3.
24. Clements, supra note 21 at para 8
25. Clements, supra note 21 at para 9.
26. Clements, supra note 21 at para 10.
27. Clements, supra note 21 at paras 38-39.
28. Ediger v. Johnston, 2013 SCC 18 (CanLII), [2013] 2 SCR 98 [Ediger]
29. Ibid at para 36.
30. Ricottone v. Long, 2025 BCSC 1388 at para 141.