Legal Definitions - Unascertainable Cause

Unascertainable Cause refers to a specific legal situation in negligence cases where multiple parties have acted negligently, and a single, indivisible injury has occurred, but it is impossible for the injured party (the plaintiff) to prove which specific negligent act caused their harm. In such circumstances, the legal system shifts the burden of proof from the plaintiff to each of the negligent parties (the defendants). This means each defendant must then prove that their actions *did not* cause the plaintiff's injury. If they cannot provide such proof, they may all be held responsible for the harm.

Here are some examples to illustrate this concept:

• Imagine a small town whose drinking water supply becomes contaminated with a specific industrial chemical, leading to a cluster of severe health issues among residents. Two different factories, Factory A and Factory B, are located upstream and both negligently discharge the exact same chemical into the river that feeds the town's water treatment plant. While it's clear the residents' illnesses are linked to the chemical, forensic analysis cannot definitively determine whether the contamination originated solely from Factory A, solely from Factory B, or a combination of both, as the chemical is identical and the injury (illness) is singular. In this scenario, the residents (plaintiffs) cannot pinpoint which factory's specific negligence caused their individual illnesses. The principle of Unascertainable Cause would apply, shifting the burden to Factory A and Factory B to each prove that their discharge *did not* cause the residents' health problems.

• Consider a hunting accident where two hunters, Mark and Sarah, are both negligently firing their rifles in the same general direction without confirming a clear target. A third person, David, who was walking through the woods, is struck by a single bullet and suffers a serious injury. Forensic examination confirms the bullet came from the type of rifle used by both Mark and Sarah, but due to the simultaneous firing and the nature of the injury, it is impossible to determine which hunter's specific bullet hit David. David has a single injury, but cannot identify which of the two negligent hunters fired the shot. Under Unascertainable Cause, David (the plaintiff) would not need to prove which hunter shot him. Instead, the burden would shift to Mark and Sarah (the defendants) to each prove that their bullet *did not* strike David.

• Picture a large commercial building under construction where several independent contractors are working on different floors. Contractor X's crew on the 8th floor negligently leaves tools unsecured near the edge, and Contractor Y's crew on the 10th floor also negligently leaves tools unsecured. A construction worker on the ground below is severely injured by a falling wrench. The wrench is a common type used by both crews, and due to the height and impact, it's impossible to determine which floor it fell from or which specific crew was responsible for that particular wrench. The injured worker (plaintiff) cannot prove whether Contractor X or Contractor Y was responsible for the specific wrench that caused their injury. Applying Unascertainable Cause, the burden would shift to both Contractor X and Contractor Y to prove that their negligence *did not* cause the worker's injury.