As stated previously, the plaintiff in a tort action bears the burden to prove his or her case. It must be shown that he or she sustained an injury as a result of a tortfeasor’s negligence (see “Causation”). Failure to establish the chain reaction between tort → accident → injury will lead to the dismissal of the claim. Except in special circumstances, the burden will be met when the plaintiff proves, on a balance of probabilities, that ‘but for’ the negligent act, he or she would not have sustained the injury. That legal test is relied upon to establish both the nexus between the negligent act and the accident and the nexus between the accident and the injury.
However, courts of law who sit on these cases are often concerned with more than just past events like who caused the accident and what injuries followed. They also have to assess the loss sustained by the plaintiff and provide compensation in replacement (see “Pecuniary Damages vs Non-Pecuniary Damages”). The damages may extend over a long period of time, before and after the trial; past and future events have their own specificities. As explained in Athey v. Leonati,  3 SCR 458 paras 26-28:
The respondents argued that the trial judge’s assessment of probabilities in causation was similar to the assessment of probabilities routinely undertaken by courts in adjusting damages to reflect contingencies. This argument overlooks the fundamental distinction between the way in which courts deal with alleged past events and the way in which courts deal with potential future or hypothetical events.
Hypothetical events (such as how the plaintiff’s life would have proceeded without the tortious injury) or future events need not be proven on a balance of probabilities. Instead, they are simply given weight according to their relative likelihood […]. For example, if there is a 30 percent chance that the plaintiff’s injuries will worsen, then the damage award may be increased by 30 percent of the anticipated extra damages to reflect that risk. A future or hypothetical possibility will be taken into consideration as long as it is a real and substantial possibility and not mere speculation […].
By contrast, past events must be proven, and once proven they are treated as certainties. In a negligence action, the court must declare whether the defendant was negligent, and that conclusion cannot be couched in terms of probabilities. Likewise, the negligent conduct either was or was not a cause of the injury. The court must decide, on the available evidence, whether the thing alleged has been proven; if it has, it is accepted as a certainty […].
While in one case the thing is established as a fact (i.e. a certainty), in the other it is set as a contingency, a possibility. The approach to each is very different, both from a practical and conceptual point of view.
The New Brunswick Court of Appeal, in Cleary v. McCluskey, 2002 NBCA 45, dealt with the evidentiary burden in respect to both past and future events. The trial judge assessed the nexus between the accident and a condition of fibromyalgia, as well as the nexus between the accident and the decision of a young lawyer to work in an administrative position instead of pursuing a legal career. On both counts, the trial judge could not find the evidentiary basis for a nexus between the accident and the resulting events alleged. These decisions were upheld by the unanimous bench (paras 23-25). The Court then turned to the claim for future losses. It confirmed the ‘actuarial method’ for the calculation of ‘pecuniary general damages’ (paras 26-27), which implies a rational connection between the invoked scenario and the evidence presented. Regarding future loss of earning capacity, the Court repeated that “it must be shown that there is a real and substantial possibility that the injured party will suffer lost earnings or profits” (para 28). Given the prior findings of fibromyalgia and career choice unrelated to the accident, the bench was at a loss to explain any award for future loss of income. Therefore, even though future events are not proven on a balance of probabilities, they must still flow from the negligent act and the accident; where causation is not established in fact, it becomes difficult to maintain a future loss claim in relation to the original tortious act.
Causation was not at play in Vincent v. Abu-Bakare, 2003 NBCA 42; the Court of Appeal was concerned strictly with whether there was a ‘real and substantial possibility’ of a future loss of income. The plaintiff argued that he would not be able to pursue his carpentry and horse training activities after his retirement, and that he would have to retire early because of the accident. However, he failed to call expert evidence to calculate his claim (paras 40 & 65). The unanimous bench repeated its opinion that there is “broad support in Canadian jurisprudence for the view that proof of a real and substantial possibility of lost earnings or profits is, generally, a condition precedent to any award of pecuniary general damages for loss of earning capacity” (para 50; see para 55). It added (paras 57-61):
If pecuniary general damages for loss of earning capacity were untethered to the risk of future lost earnings or profits, their quantum would be wholly arbitrary. In addition to being irregular and unpredictable, awards would not be subject to meaningful appellate review since there would be no parameters for their determination. […] In my view, such a result is unacceptable, having particular regard for the fact that the losses in question are pecuniary in nature.
The common law – certainly in its modern state – seeks to reflect reason. It rightly finds arbitrariness repugnant. Of course, trial judges routinely – and quite properly – make judgment calls to identify which future scenario would most likely have unfolded but for the accident, and which will most likely play itself out in the aftermath of the trial. There is, however, an important difference between a logical choice of scenarios and quantum based on identified data (degree of risk, baseline income, duration of loss, etc.) and the picking of a totally arbitrary global sum out of thin air. […]
It is axiomatic that mere difficulty in quantifying a proven loss cannot stand in the way of fair compensation. That basic principle, however, was never intended to lift from the plaintiff’s shoulders the burden of establishing by admissible evidence, at the very least, a range of rationally defensible quantums for the future pecuniary loss claimed. […] Too often trial judges are being asked by plaintiffs to award damages for inadequately proven future pecuniary losses. The solution does not lie in making an arbitrary award, whether free-standing or dissolved in the non-pecuniary general damages. The principled approach is to award only nominal pecuniary general damages, the claimant having failed to prove his or her loss.
The quantum of pecuniary general damages for loss of earning capacity must fall within a range of present values of future pecuniary loss that is rationally connected to the evidence. […] The trial judge’s identification of a range will invariably withstand appellate scrutiny if it is susceptible to some logical analysis. The trial judge’s choice of a particular quantum within the range mentioned above should, in all but the most exceptional cases, be treated as an unimpeachable judgment call. In carrying out the often-difficult task of quantifying damages – whether in tort or contract law – courts occasionally have no alternative but to resort to guesstimates or approximations. That process will not be faulted so long as it is both necessary and susceptible to logical analysis.
The court must apply a two-step process in the calculation of pecuniary general damages for loss of earning capacity. First, the court must make an estimate of the chances that a loss of earnings or profits will occur. If the possibility of such a loss is speculative or negligible, the court need go no further; the claim has not been proven. If the possibility is real and substantial, the court must reflect the chances of that loss occurring in the amount of damages that it awards. […] What the court quantifies is the present value, as of trial, of the risk of future lost earnings or profits. If, for example, the court were to settle upon a 25% chance that the working plaintiff will be forced to retire two years before the planned date, the pecuniary general damages for loss of earning capacity would be the present value of 25% of any consequential losses.
The same principle evidently applies to general pecuniary damages for loss of valuable services and costs of care: Wallace v. Thibodeau, 2008 NBCA 78 para 33. In Vincent, supra, the Court of Appeal could find evidence to support only an award of nominal damages, at least as far as early retirement, carpentry and horse training were concerned (paras 67 & 75).
The quantum of future losses also depend on what is known as contingencies, which can be either positive or negative. As explained in Wallace, supra paras 39-41:
Contingencies are factors that may influence the quantum of damages. Those operating to reduce quantum are referred to as “negative” contingencies. Negative contingencies may be general or specific.
General contingencies, whether negative or positive, are “as a matter of human experience […] likely to be the common future of all of us” […]. The traditional view […] is that they may be considered by the assessing court in the absence of expert evidence regarding their likely occurrence and impact on the quantum of damages. General negative contingencies include the risk of disability common to all […]. In his oft-referenced textbook, Personal Injury Damages in Canada, 2nd ed. […], Professor Cooper-Stephenson concludes […] that on balance a 5% reduction for this general risk would be appropriate. I respectfully agree.
Specific contingencies are influential factors that are personal to the individual claimant. Unlike general contingencies, they require proof, and the burden of proof rests on the party seeking to benefit from their application.
The same can be said of positive contingencies, like possible advancement and promotion in employment, prolonged life, etc. Each will influence the quantum of damages accordingly.
Lawyers tackling issues of past and future events must therefore be mindful of the distinction in the applicable tests. Although the proof of future events may appear somewhat easier, it does not relieve the plaintiff from presenting sufficient compelling evidence to support his or her claim.