Legal Definitions - intervening force

An intervening force refers to an independent event or action that occurs *after* an initial wrongful act or negligence by one party, but *before* the resulting harm or injury to another party. This force contributes to the final outcome and can sometimes be significant enough to break the chain of causation, potentially relieving the original wrongdoer of liability for the ultimate harm.

Here are some examples to illustrate this concept:

• Example 1: Highway Collision

  Imagine a scenario where a truck driver negligently leaves their broken-down vehicle partially blocking a lane on a dimly lit highway without setting out proper warning flares or cones. An hour later, a second driver, who is speeding and distracted by their phone, swerves and collides with the disabled truck, causing severe injuries to themselves. The truck driver's initial negligence created a dangerous situation. However, the second driver's speeding and distracted driving constitute an intervening force. A court would need to determine if the second driver's actions were so reckless and unforeseeable that they broke the causal link between the truck driver's initial negligence and the resulting injuries, potentially reducing or eliminating the truck driver's liability.

• Example 2: Construction Site Accident

  A construction company leaves a deep excavation uncovered and inadequately marked overnight, which is a negligent act. During the night, a group of vandals deliberately removes the few warning signs and barricades that *were* present around the trench, making it even more hazardous. A pedestrian, unaware of the danger, then falls into the trench and sustains serious injuries. The actions of the vandals in removing the safety measures represent an intervening force. While the construction company was negligent in leaving the trench exposed, the vandals' intentional act significantly worsened the hazard and directly contributed to the pedestrian's fall. The legal question would be whether the vandalism was a foreseeable consequence of the company's initial negligence, or if it was an independent, superseding act that broke the chain of causation.

• Example 3: Defective Product and Misuse

  A manufacturer produces a batch of electric kettles with a subtle wiring defect that makes them prone to short-circuiting under specific conditions. A consumer purchases one of these defective kettles. While using it, they ignore clear instructions to only fill the kettle to the "max fill" line and instead overfill it significantly, then place it on an uneven surface where it tips slightly. The kettle then short-circuits and causes a small fire due to the combination of the defect and the consumer's misuse. The consumer's actions of overfilling and improperly placing the kettle, despite instructions, represent an intervening force. Although the kettle had an initial manufacturing defect (the manufacturer's negligence), the consumer's subsequent, improper use directly contributed to the short-circuit and fire. A court would analyze whether the consumer's misuse was so extreme or unforeseeable that it superseded the manufacturer's initial defect as the primary cause of the damage.