What is the Bourque and Thiessen approaches to determining whether a plaintiff was injured as a result of the collision between two defendants?

Both approaches under consideration ensure that the plaintiff is fully compensated for her injuries in circumstances such as those here. The Bourque approach attributes to each of the defendants his or her share of the responsibility in accordance with the trial judge's assessment of causation based on the knowledge available at trial. The exception, stated in Bourque, is where the condition created by the earlier incident is quiet and non-symptomatic, in which circumstances the case is treated as one of thin skull. The disadvantage of the Bourque approach arises because the cumulative effect only becomes evident after a subsequent accident. In the event that the action arising out of the earlier accident has been settled or tried, there is a risk that if the third defendant takes only his share of the responsibility the plaintiff will be under compensated. The Long v. Thiessen approach, on the other hand, ensures full compensation, but ignores the reality of the situation, known at the time of trial, which is unfair, in this case, to the final defendant.