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VOL. 77 PART 2 MARCH 2019
Instead, what was referred to in that decision as “hypothetical” or “future”
events will be taken into consideration so long as they are a “real and substantial
possibility” and not “mere speculation”.6 They are then given weight
according to their relative likelihood, having regard to all the contingencies.
Athey could be taken as suggesting that hypothetical or future events
include those that lie in the future at the time of the accident but lie in the
past at the time of trial. However, the court made no mention of a standard
of proof for “past hypothetical events”. It said only that past events, such as
whether the defendant’s conduct was negligent and if so whether that negligent
conduct was a cause of the injury, must be proven on a balance of
probabilities, and once proven on this standard, are to be treated as certainties.
7 The court did not address the fact that a past hypothetical alternative
course of conduct may be offered to establish that the defendant’s conduct
was negligent, nor did it discuss the fact that post-accident, pre-trial hypothetical
events may be relevant to assessing pre-trial loss and damage.
The Athey approach to hypothetical or future events has been referred to
as a proportional-causation exception to the usual all-or-nothing approach
to causation, an exception justified by difficulties of proof.8 It may be
viewed, like other modifications noted below, as a means of mitigating the
burden lying on a plaintiff in matters of causation.
In Grewal, the B.C. Court of Appeal acknowledged that for the purpose of
assessing damages, past hypothetical events are not to be determined on a
balance of probabilities, as it had twice previously held in 2015.9 For the purpose
of assessing damages, as opposed to establishing liability, hypotheses
regarding both past and future events need only be established as “real and
substantial possibilities” to be given recognition, subject to contingencies
and in proportion to the likelihood they would have occurred or will occur
However, not all past hypothetical events are treated this way. Hypotheses
regarding potential alternative courses of past events for liability purposes
must be established on a balance of probabilities.
In Sabourin Estate v. Watterodt Estate,10 it was argued that an aircraft collision
would have been avoided had the airport radio operator given further
warning to an approaching pilot of the proximity of a second aircraft, one
whose pilot had already announced his presence on the same channel. The
majority upheld the trial judge’s decision, declining to impose liability on
the radio operator because the hypothesis offered had not been established
on a balance of probabilities. It rejected the contrary view, taken by Lambert
J.A. in dissent, as “speculative” and accepted the trial judge’s conclusion
as supported by the evidence. Justice Lambert observed that all