When will a judge exercise his or her discretion with respect to costs in a personal injury case?

The Court of Appeal, in Moore v. Dhillon, supra, dealt with the power of a judge to exercise his or her discretion with respect to costs where there is a potential for injustice as follows at p. 74: While the s. 3 prima facie rule may work well in cases where liability is divided between defendants only, and where there are cross-claims between plaintiff and defendant, there is potential for injustice when the prima facie rule is applied without exercise of discretion in cases, such as this, where division of fault is as between a successful personal injury plaintiff and a defendant who has suffered no injury or damage, or who has already been fully compensated for any injury or damage suffered.