Dateline: May, 2007, Issue 6

How does the aggregation of plaintiffs influence liability and damage awards?

The advent of the modern mass tort trial has pitted individualized justice against judicial concern for efficiency, leading to the aggregation of cases. Horowitz and Bordens have examined the effect of aggregating plaintiffs on liability decisions and damage awards in mass toxic tort litigation.

In 1988, Horowitz and Bordens reported that the presence of a severely injured plaintiff increases the awards to all of the aggregated plaintiffs. The severely injured plaintiff received a lesser award when aggregated with plaintiffs who had less severe injuries, while the least injured plaintiff received a higher award when aggregated. When judging multiple plaintiffs, jurors tend to lump or blend differentially worthy plaintiffs.

In 2000, Horowitz and Bordens looked at cases involving 1, 2, 4, 6 and 10 plaintiffs. Plaintiffs were less likely to prevail in trials involving 1 or 2 plaintiffs than when aggregated in a 4-, 6-, or 10-plaintiff group. Less comparative fault was assigned to the plaintiffs as the number of plaintiffs aggregated in a trial increased (27% fault in the 10-plaintiff trial versus 60% in the 1 plaintiff trials). Damages peaked for individual plaintiffs in the 4-plaintiff trial: individual plaintiffs received the lowest damages in the 1- and 2-plaintiff trials, higher damages in the 6- and 10-plaintiff trials, and the highest damages in the 4-plaintiff trials.

Liability judgments against the defense are more likely when 4 or more plaintiffs are aggregated, the aggregation of plaintiffs increases damage awards for all but the most severely injured, and the highest return per plaintiff occurs when 4 plaintiffs are aggregated.

Source Horowitz, I. A., & Bordens, K. S. (1988). The effects of outlier presence, plaintiff population size, and aggregation of plaintiffs on simulated civil jury decisions. Law and Human Behavior, 12, pp. 209-229.

Source Horowitz, I. A. (2000). The consolidation of plaintiffs: The effects of number of plaintiffs on jurors' liability decisions, damage awards, and cognitive processing of evidence. Journal of Applied Psychology, 85, pp. 909-918.