Causation is a required element in many U.S. civil claims. To establish it, courts apply two primary legal standards: actual cause and proximate cause. A plaintiff must show that the harm would not have occurred but for the defendant’s conduct and that the harm was a foreseeable result of that conduct.
To fully get to know about causation, it is important to understand how these standards function together. This article explains the but-for test, the substantial factor test used in certain jurisdictions, and the role of foreseeability in limiting liability. It also outlines how courts evaluate evidence to determine whether causation has been legally proven.
Legal Standards of Causation According to the Law
Actual Cause
The actual cause is about whether what someone did directly caused the injury. Lawyers use the “but-for” test a lot here. It asks: “But for what this person did, would the injury have happened?”
If the answer is no, then the action probably caused the harm. For example, if someone runs a red light and hits a pedestrian, the pedestrian wouldn’t be hurt but for the car running the red light.
Another way courts decide on causation is the substantial factor test. This is for when more than one thing caused the injury. For example, if two people start a fire which ends up burning down a house, since both fires played an role in the destruction, both parties can be held responsible.
Proximate Cause
Proximate cause is harder to deal with. It’s not just that someone’s action caused the injury. It has to be something an everyday person would understand to be risky.
If the actions of a person did not cause the damage, then the law might say it doesn’t count.
For example, if someone causes a car accident, and while the injured party is waiting for help, they are struck by lightning. Lightning in this case is not directly related and is a random event, for which the driver who caused the accident cannot be held responsible.
Intervening and Superseding Causes
The law also has rules about intervening and superseding causes. An intervening cause happens after the first act.
It only breaks liability if it’s a superseding cause, meaning it’s totally unexpected and independent. If it’s foreseeable, the original person still pays.
Eggshell Plaintiff Rule
Courts also follow the eggshell plaintiff rule. If a person has a preexisting condition or unusual vulnerability, the defendant is still responsible for the full extent of the harm caused. Even if a healthier person would have suffered less damage, the defendant remains liable for all resulting injuries.
Why Does It Matter If There Are Multiple Causes?
Injury cases often involve more than one contributing act. Sometimes two separate actions occur at the same time, and each may be sufficient to cause the harm. In those situations, a defendant can still be held liable if their conduct was a substantial factor in producing the injury.
Other times, harmful acts occur in sequence. A later wrongdoer is not relieved of responsibility simply because an earlier act already caused damage. When multiple acts combine to produce a single injury, courts focus on whether each defendant’s conduct materially contributed to the outcome.
Courts do not apply fixed numerical percentages to determine causation. Instead, the key question is whether the defendant’s conduct was a substantial factor in causing the harm. If it was, liability may follow, even when other causes are also present.
How Do Courts Decide on Causation?
Courts use a balance of probabilities. If they think it’s more likely than not that the person’s negligence caused the injury, they are responsible. This is called proving causation by preponderance of evidence.
Even if the harm might have happened anyway, if the negligent person’s actions contributed substantially, they can be held fully liable.
Key Takeaways
- Causation links what someone did wrong to the person getting hurt.
- Actual cause asks a simple question: would this person have been hurt if the other person hadn’t done that action?
- Proximate cause asks: could someone have seen this kind of harm coming? Was it obvious that it might happen?
- Sometimes other events lead to harm. Those are called intervening or superseding causes. They can change who is responsible.
- The eggshell plaintiff rule means that if someone is hurt, even if they had pre-existing conditions, the person who caused harm still has to pay for all the damage.
