Legal Definitions - independent intervening cause

An independent intervening cause refers to a new, separate, and unforeseeable event that occurs after an initial wrongful act and breaks the direct link, or "chain of causation," between that initial act and the ultimate harm suffered. For an event to be considered an independent intervening cause, it must be so powerful and unrelated to the original act that it essentially becomes the sole cause of the final injury, relieving the original wrongdoer of liability for that specific harm.

Here are some examples to illustrate this concept:

• Scenario: Negligent Driving and a Natural Disaster

  Imagine a driver, Sarah, negligently runs a stop sign and collides with another car, driven by Mark. Mark suffers a broken arm, which is a direct result of Sarah's negligence. While Mark is being transported to the hospital in an ambulance, an unprecedented and sudden earthquake strikes, causing a bridge to collapse. The ambulance, caught on the collapsing bridge, is severely damaged, and Mark sustains a severe spinal injury, completely unrelated to his broken arm.

  Explanation: Sarah's negligent driving is the initial wrongful act that caused Mark's broken arm. However, the sudden and unforeseeable earthquake is an independent intervening cause. It is a new, separate event that was not a foreseeable consequence of Sarah running a stop sign. While Sarah would be liable for Mark's broken arm, the earthquake would likely break the chain of causation for the spinal injury, meaning Sarah would not be held responsible for the harm caused by the earthquake.

• Scenario: Unsecured Construction Site and Vandalism

  A construction company, BuildCo, negligently leaves a construction site unsecured overnight, failing to lock gates or secure valuable equipment. This initial negligence creates a risk of theft or minor damage. However, during the night, a group of vandals, completely unrelated to BuildCo's negligence, breaks into the site and intentionally detonates explosives, causing catastrophic damage to the partially built structure and an adjacent property.

  Explanation: BuildCo's negligence in securing the site created a general risk. However, the deliberate act of vandalism involving explosives is an independent intervening cause. It is a new, separate, and extreme act that was not a foreseeable consequence of merely leaving a site unsecured. While BuildCo might be liable for any foreseeable theft or minor damage due to their negligence, the intentional and extreme act of detonating explosives would likely break the chain of causation, relieving BuildCo of liability for the catastrophic damage caused by the vandals.

• Scenario: Medical Malpractice and a Freak Accident

  A surgeon, Dr. Lee, negligently performs an operation, leaving a patient, Emily, with a treatable but serious infection. This infection requires Emily to remain hospitalized for an extended period. While recovering in her hospital room, a rare and unpredictable electrical surge causes a faulty ceiling light fixture to fall directly onto Emily's head, resulting in a severe concussion and permanent neurological damage, completely unrelated to her infection or the initial surgery.

  Explanation: Dr. Lee's negligence caused Emily's infection. However, the unexpected electrical surge and falling light fixture constitute an independent intervening cause. This event was a new, separate, and unforeseeable accident that was not a consequence of Dr. Lee's surgical error. Dr. Lee would be held responsible for the harm caused by the infection, but the falling light fixture would likely break the chain of causation for the concussion and neurological damage, as it was an independent event.