Coping with Complex Causation Information in Personal Injury Cases

(2013) 41 Advocates Quarterly 149

30 Pages Posted: 11 May 2013 Last revised: 12 Sep 2014

See all articles by Erik S. Knutsen

Erik S. Knutsen

Queen's University Faculty of Law

Date Written: June 2013


Nowadays, everything is always someone else’s fault. In the fault-based tort system in Canada, that often translates into injury cases exhibiting greater tendencies for presenting with complex information about how an injured victim’s injuries were caused. In many instances, the additional causation information is unwanted, irrelevant and muddies the task of applying causation doctrine to the facts of a particular case. This unwanted information about causation that distracts from the application of causation law to case facts can be thought of as “causal noise.” It needlessly complicates an already complicated process. Injured accident victims often have pre-existing injuries or health conditions that confounds the causal inquiry necessary in order to bring a tort claim under negligence law. Some victims have the misfortune of experiencing multiple, successive accidents over time which affect end result injuries and the healing process. It can often seem impossible to sort out the multiple causal factors – both negligent and non-negligent – that result in an injured victim’s total constellation of symptoms comprising his or her injury. These multiple competing and contributing causal factors can make up causal noise. Their very existence distracts the fact-finder and litigants with complicated legal doctrine and intricate factual scenarios when, in fact, the inquiry is supposed to be one about the effect of the defendant’s at-fault behaviour on the plaintiff. This article attempts to offer some solutions to containing causal noise by simplifying the thinking about causation so as to maintain tort law’s fault-based compensatory goals.

Part I of this article is a causation primer, discussing the present development of causation doctrine in Canadian negligence law. This Part sets the backdrop for the normative discussion to follow. Part II of this article touches on a number of issues germane to personal injury cases including which doctrinal test to use – “but for” or material contribution – and how to compartmentalize the “but for” test into an understandable concept useful in cases exhibiting causal noise. Additionally, the article advocates for trial judges to revitalize the approach of drawing causal inferences in cases involving causal draws, which are cases where the evidence appears equally balanced, but insufficient, for both plaintiff and defendant to prove causation to the requisite degree. Finally, the article sketches a framework for sorting out causal noise in difficult cases involving multiple competing causal factors. The framework is applicable not only in terms of causation but also in terms of assessing a defendant’s responsibility for the extent of a victim’s harm and the responsibility to pay for that harm.

Suggested Citation

Knutsen, Erik S., Coping with Complex Causation Information in Personal Injury Cases (June 2013). (2013) 41 Advocates Quarterly 149, Available at SSRN:

Erik S. Knutsen (Contact Author)

Queen's University Faculty of Law ( email )

Macdonald Hall
128 Union Street
Kingston, Ontario K7L 3N6
613-533-6000 ext. 78360 (Phone)
613-533-6509 (Fax)


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