What is the test for determining the quantum of damages for negligence?

Once causation in fact and law has been established, the analysis shifts to the rules of damages which determine the quantum of the defendant’s liability. The fundamental principle in assessing tort damages is that the quantum should be that which is required to place the plaintiff in his or her original position, i.e. the position he or she would have been in absent the defendant’s negligence: Athey, at para. 32. The defendant need not put the plaintiff in a better position than his or her original position and should not compensate the plaintiff for any damages he or she would have suffered anyway: Blackwater v. Plint, 2005 SCC 58, at para. 78. The analysis requires a determination of the plaintiff’s position after the negligence and an assessment of what the plaintiff’s original position would have been, and it is the difference between these positions that represents the quantum of the defendant’s liability: Athey, at para. 32.