Legal damages for losses of chances

Traditionally, damages for torts have been awarded on an all-or-nothing basis. In malpractice suits, however, a growing number of courts are holding doctors liable for negligent acts that reduces a patient's chance of survival, even if the patient's chances for recovery have already been less than 50%. For lack of a general principle, a disparate variety of loss of chance rules seems in use. To provide some more systematic guidance, the present paper proposes to look directly at the interaction between the injurer's act and a random move of nature that captures the uncertainty. For any given move of nature, damages are still awarded on an all-or-nothing basis. If however, for lack of observability, moves of nature cannot sufficiently be distinguished, averages of correct damages over observable events are taken. While the scheme aims at compensatory goals of tort law, as a by-product, it also generates efficient precaution incentives provided that due care standards obey the Hand Formula.