C.A. Says “One in Four” Chance of Avoiding Accident Doesn’t Meet Causation Threshold

In a brief but interesting decision handed down today, the Court of Appeal allowed an appeal by a third party who had been found liable at trial. The trial judge had found  had that tortfeasor not been negligent, another tortfeasor’s chances of avoiding an accident would have been increased by a factor of “one in four”. The Court of Appeal held that this did not establish causation, so as to ground a finding of liability.

The case is Lawson v. Sullivan and the action arose from a rear-end collision in which the plaintiff’s vehicle was stopped on a roadway because Hydro Ottawa workers were working on overhead lines. The defendant Sullivan, whose car had struck the plaintiff’s vehicle, brought a third-party claim for contribution or indemnity against Hydro Ottawa, arguing that Hydro had failed to take adequate measures to alert approaching motorists that its operations were disrupting traffic.

The action was tried by Mr. Justice David McWilliam, who found 25% liability on the part of Hydro Ottawa. His decision rested on this finding:

I am satisfied that had Mr. Sullivan’s inattentiveness been jarred by flashing lights ahead, his chances of being able to stop in time would have increased by at least one in four given the speed at which he was driving which was not fast, and that is why I have assessed Hydro’s contributory negligence at 25 percent in all of the circumstances.

On the appeal, both sides conceded that the “but for” test of causation governed. Applying that test, the Court of Appeal ruled that the trial judge’s findings fell short of establishing causation. It noted that a one in four chance of avoiding the unfavourable outcome (here, the rear-end collision) meant that the likelihood of so doing was less than fifty-fifty. As a result, it could not be said that “but for” Hydro’s conduct, the accident would, more likely than not, have been avoided: “[w]ithout causation there can be no liability.”

On this basis, the Court allowed Hydro Ottawa’s appeal and dismissed the third party claim with costs.

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