What is Proximate Cause in a Car Accident Case?

Few legal concepts are as poorly understood—by lawyers and non-lawyers alike—as proximate cause. Proximate cause is simply part of a bigger legal concept known as "causation." Causation, in turn, is an essential element of any car accident (or other legal) claim.

So, what does proximate cause do? Imagine causation as a chain that connects an act or event (like careless driving) to an outcome (like a car wreck). Proximate cause is a tool—think of a pair of scissors—that's used to cut the causation chain when it gets too long.

Despite the widespread misunderstanding, proximate cause is a straightforward concept. We'll walk you through the basics. We begin with a general overview of causation in car accident injury claims. From there, we'll zero in on proximate cause and explain how it works.

What Is Causation in a Car Accident Claim?

In the overwhelming majority of car accident cases, the injured person must prove these elements to collect compensation ("damages," in the language of the law):

• the other driver was negligent (careless)
• the injured person suffered an injury, and
• the injury was caused by the other driver's negligence.

Our concern is with the third element, causation. What does it mean to say that one thing (someone's negligence) caused another thing (another person's injury)? To answer that, let's consider some examples.

Three Causation Examples

Example 1: Jeff carelessly ran a stop sign and hit Jane's car, breaking her leg. The cause of Jane's broken leg—Jeff's careless driving—is clear.

Example 2: Jeff picked up a case of food poisoning eating dinner at his favorite fast food restaurant one night. The next morning, he felt very ill but he couldn't skip work. While on his way to the office, Jeff took his eyes off the road to look for a bottle of ibuprofen in his car. He ran a stop sign and collided with Jane's car, breaking her leg.

Example 3: Jeff had to drop his young daughter off at school, but she was running late because she misplaced one of her school books and had to search the house for it. After getting his daughter to school, Jeff's attention was distracted when he called the office to report that he'd be a few minutes late. Jeff ran a stop sign and collided with Jane's car, breaking her leg.

Who Caused the Wreck?

If you were the lawyer representing Jane, who would you tell her to sue in each example? Who caused Jane's injury?

Example 1 is the easy case. Jeff's negligent driving was the immediate, and only, cause of the wreck.

How about Example 2? It makes sense that Jeff, the most obvious cause, would be on the hook. But the wreck probably doesn't happen absent Jeff being served tainted food by the restaurant. Does it make sense to say that the restaurant's negligence also was a cause of the collision?

Example 3 is even more troubling. Had Jeff's daughter not misplaced her book, Jeff would have been on time. He wouldn't have needed to call the office and might well have avoided the accident. Should Jane sue only Jeff? Or should she pursue a claim against Jeff's daughter?

Examples 2 and 3 illustrate why causation can be a challenge. Let's find out how the law tackles this problem.

Causation Equals Actual Cause Plus Proximate Cause

You don't have a viable car accident claim unless you can prove causation. Causation has two elements. You must show that someone else's negligence was both the actual cause of your injury, and the proximate cause of your injury. Absent either one you have no causation, and thus no claim.

Actual Cause

Also known as "but-for" cause, actual cause asks: Would "B" have happened without (but-for) "A"? In our three examples, the collision and Jane's injury don't happen without (but-for) Jeff's distracted driving. In each instance, his carelessness is an actual cause of the collision.

There can be more than one actual cause for an accident or injury. Consider Example 2. Jeff's food poisoning—presumably brought about by the restaurant's negligent food preparation—also was a but-for cause of Jane's injury. After all, but for being ill, Jeff wouldn't have been distracted looking for medicine and he could have seen the stop sign. The restaurant's negligence was another actual cause of the accident that left Jane injured.

The same can be said for Example 3. Had Jeff's daughter not misplaced her book, Jeff would have been on time. He wouldn't have needed to call his office and could have seen the stop sign, avoiding the collision. Jeff's daughter's careless loss of her school book was another actual cause of the wreck.

The Problem With Actual Cause

By now, you might be seeing the problem with actual cause: It always exists. In other words, it's possible to draw a chain of actual, but-for causation between any two events. Consider this simple example. Jeff couldn't have hit Jane had he never been born. Jeff's birth, technically speaking, is a but-for or actual cause of his collision with Jane. So too, there wouldn't have been an accident had Jeff's mother never been born. Her birth is a but-for cause as well.

We can trace this chain of causation as far back as we please, all the way to the formation of the Earth. Without some way to break the causal chain, our system of courts and justice would grind to an unworkable halt. Proximate cause is the tool that breaks the causal chain.

Proximate Cause

Proximate cause looks at the relationship between an actual cause and the outcome in question, and cuts off the causal chain at the point where it gets so long that it doesn't make sense. How does proximate cause know where to cut the causation chain? The rules vary from state to state but in general, states use a couple of tests: The substantial factor test and the foreseeability test.

The substantial factor test. To decide whether an actual cause was also the proximate cause of a car accident, this test asks whether that actual cause was a substantial factor in causing the wreck. Did that cause play a significant role in causing the collision? A substantial factor need not be the sole or even the predominant cause of an outcome, but it must be more than a remote, distant, or trivial cause.

The foreseeability test. This test asks whether a particular result (like a car accident) was a reasonably foreseeable consequence of some actual cause. For instance, it's foreseeable that a driver who's texting while driving might lose track of the road and cause a collision. But at some point, the links in the chain of actual causation become too remote or contingent in time or place to say that they were the proximate cause of an auto accident.

Note, importantly, that both substantial factor and foreseeability aren't "bright-line" tests that produce a clear, indisputable result. Each requires judgment and balancing of the relevant facts and circumstances. Rather than a hard cutoff point, they're more likely to produce a range of possible, and more or less likely, proximate causes.

How Do the Tests Work?

Example 1: Jeff's careless driving is the proximate cause of the accident. His negligence was a substantial factor in causing the wreck. It's also easy to foresee that carelessly running a stop sign might lead to a collision.

Example 2: Was the restaurant's negligent food handling a substantial factor in causing the wreck? Jeff certainly would argue so, but pinning Jane's misfortune on some tainted fast food seems like a reach. Is it foreseeable that a case of food poisoning might lead to distracted driving and a collision? Perhaps, but reasonable minds might just as easily conclude that eating bad food was too remote an occurrence to be the proximate cause of this car accident.

Example 3: While Jeff's daughter's carelessness was an actual cause of the wreck, proximate cause is doubtful at best. The misplaced school book seems to be a remote or trivial cause that was far too contingent to be considered a substantial factor leading to the collision.

If you were on a jury hearing this case, would you find that a lost book might foreseeably cause Jeff to run a stop sign and hurt someone? Does blaming the mishap on a child's negligence under these circumstances make sense? Consider all the intermediate steps between "lost book" and "car accident." Jeff chose to let his daughter look for the book instead of sending her to school without it. That made him late. His tardiness caused him to call the office. While making the call, he became distracted, which caused him to miss the stop sign and hit Jane's car.

Finding that the lost school book proximately caused the accident is simply a bridge too far. Proximate cause will cut off the actual causation chain well before that point.