Causality and Incentives with Multiple Tortfeasors

For a tortfeasor to be liable for a victim's loss, the tortfeasor's negligence must have caused the loss. In the context of multiple tortfeasors, this is generally taken to mean that but-for the tortfeasors negligence, the loss would not have occurred, given the acts by other tortfeasors. In the law and economics literature on causality, it has been claimed that this but-for test of causality does not jeopardize incentives for optimal precaution, not even when each tortfeasor's negligence is a sufficient cause of the victim's loss. We demonstrate that this claim is not generally true, and that it fails to hold in particular in the case of multiple sufficient causes. We suggest an alternative test of causality which inquires whether the victim's loss would have occurred were it not for the tortfeasor's negligence, if he other tortfeasors had taken due care. We demonstrate that this alternative test is compatible with optimal incentives subject to an unrestrictive condition.