What Is Causation in a Personal Injury Case?

Say you were hurt by someone else's negligence. Maybe a careless driver ran a red light and hit you, breaking your leg. To win your case, you'll have to prove that your injury was caused by the other driver's negligence. The law calls this "causation," and it's an essential part of every personal injury claim.

Most often—as in our example above—causation is obvious. So much so that it's easy to forget causation is even an element of your claim. But don't be lulled into a false sense of security. In the rare case where causation is disputed, it can be a stone-cold claim killer.

If you have a personal injury case, you should have a basic understanding of causation. We begin by explaining what causation is and how it works. From there, we'll have a look at some situations when causation might be a problem in personal injury cases.

What Is Causation and How Does It Work?

Most personal injuries result from someone's negligence, meaning carelessness. On occasion, a person's intentional misconduct—what the law calls an "intentional tort"—leads to personal injuries. In those cases, here are the necessary elements of a personal injury claim or lawsuit:

• someone acted negligently or intentionally
• you were injured, and
• your injury was caused by that person's negligent or intentional misconduct.

Our focus is on causation, the last element. Causation has two elements, both of which must be present: Actual cause and proximate cause.

Actual Cause

Actual cause means that an act or event was a cause-in-fact or a but-for cause of some outcome. In other words, but for some act or event "A," outcome "B" doesn't happen. In the easy causation cases, spotting the actual cause (or causes—there can be more than one) for an accident or injury isn't a problem.

For example, suppose a texting driver lost track of the road, ran a stop sign, and collided with you. Their texting was an actual cause of the collision. But for the other driver being distracted by texts, they could have seen the stop sign and avoided the wreck.

As you were leaving a co-worker's year end holiday party, you slipped and fell on their icy front walk. The co-worker's failure to clear the walk of ice was a but-for or actual cause of your fall.

A negligently designed electrical switch shorted out and started a fire that destroyed your home and left you with severe smoke inhalation injuries. That defective switch was the cause in fact, or actual cause, of the short which led to the fire.

The Problem With Actual Causation

Think of actual causation as a chain that connects someone's negligent or intentional misbehavior to your injury. You don't have a viable personal injury claim without that chain. But there's a catch. The chain has to be just the right length. If it gets too long, it becomes impossible to identify with certainty the legal cause of your injury. To illustrate, let's return to the example of the texting driver who hit you.

Sam gets food poisoning. The night before he hit you, Sam, our texting driver, ate dinner at his favorite local restaurant. Unfortunately, he picked up a case of food poisoning because his dinner was undercooked. When he ran the stop sign and collided with your car, Sam was on his way to his doctor's office to get checked out. He was texting the doctor's office to let them know he was running a few minutes late.

What's the actual cause of the collision now? Clearly, Sam is on the hook because he was behind the wheel. But he wouldn't have been driving but for having eaten bad food the night before. Sam's food poisoning, caused by the restaurant's negligent mishandling of his meal, was another actual cause of the accident that hurt you.

As part of your car accident injury case, should you sue the restaurant that caused Sam's food poisoning?

Sam's daughter lost her school book. Let's complicate matters even more. Sam had to take his young daughter to school on the morning of the accident. He planned to go see his doctor after dropping her off. As fate would have it, Sam's daughter misplaced one of her school books that morning and had to search the house for it, making Sam late for his appointment.

We've just added another link to our actual causation chain. But for Sam's daughter losing her book, Sam would have been on time. Because his daughter made him late, Sam had to text the doctor's office to let them know. Sam's daughter's carelessness is yet a third actual, but-for cause of your injury.

Would you name her as a defendant (a responsible party you're suing) in your car wreck case?

The chain can keep growing forever. By now, you've probably spotted the problem with actual cause: It almost always exists. That is, you can connect almost any event to any other event with an actual causation chain.

For example, Sam's birth was an actual cause of the accident. The wreck doesn't happen but for his being born. Sam's paternal grandparents' marriage is still another but-for cause. Had they not married and had Sam's father, Sam wouldn't have been around to run into you at the intersection.

If you have the time, you can build a chain of actual causation that stretches back 4.5 billion years to the formation of the Earth. Needless to say, that could cause real problems of proof in personal injury (and other) legal cases.

At some point, actual causation becomes too remote or attenuated to be considered the legal cause of an injury. We need some way to sever the actual causation chain before it reaches that point. For that, we turn to our second causation element, known as proximate cause.

Proximate Cause

Proximate cause examines the relationship between an actual cause and its outcome, and cuts the causal chain before actual causes start getting too distant or remote. An actual cause that bears a sufficiently close and direct relation to an outcome can be considered a proximate cause, or legal cause, of that outcome. As with actual cause, there can be more than one proximate cause for an accident or injury.

So, how does proximate cause work? How does it know when an actual cause is so weak or distant that it doesn't survive the cut? The rules vary but in general, states apply one of these tests to decide on proximate cause: The substantial factor test and the foreseeability test.

The substantial factor test. This test asks whether some actual cause was a substantial factor in causing an injury. A substantial factor is one that plays a significant causal role. It doesn't need to be the sole or even the predominant cause of an outcome, but it must be more than a remote, distant, or trivial cause. An actual cause that's a substantial factor in causing some result is a proximate, or legal, cause of that result.

The foreseeability test. The foreseeability test asks whether a particular result was a reasonably foreseeable consequence of some actual cause. 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 foreseeable, and thus the proximate cause of an injury.

To continue with our examples, it's foreseeable that a driver who's texting while driving might lose track of the road and cause a collision. Is it foreseeable that food poisoning or a daughter's lost school book might lead to distracted driving and a collision? Both seem doubtful.

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.

When Might Causation Be in Doubt?

In the typical personal injury case, nearly all the focus will be on the first two elements—negligent or intentional misconduct and injury. Causation is kind of a tag-along element that's taken for granted. When the reason for an injury is clear and undisputed, no one pays causation much attention.

But there are situations when causation will rear its ugly head and be a live issue. Here are a few of the most common.

You Have Preexisting Injuries

Suppose you slip and fall on a wet substance in a grocery store aisle. The fall re-injures or aggravates a low back injury you suffered years ago at work. On these facts, causation is sure to be a big issue—maybe the deciding issue—in your injury claim.

Any time your claim involves a preexisting injury, expect the defendant to argue that whatever injury you now have was caused by the prior event or incident. We might call this the "somebody else did it" defense. The defendant's goal is to deflect as much blame for your symptoms as possible to the preexisting condition, reducing the damages they have to pay.

Several Parties Caused or Contributed to Cause Your Injury

This one shouldn't come as a surprise. When several parties' misconduct combines to cause your injury, you can count on a causation fight. The good news is that in most cases like this, you can be relatively indifferent to how the fight plays out. The defendants will fight among themselves over who has to pay you how much, but in the end you'll still collect all your personal injury damages.

When might this fight matter to you? When one or more of the defendants is:

• immune from liability—meaning shielded from legal responsibility for their own wrongdoing, or
• judgment proof—meaning without insurance or other assets to pay their share of your damages.

The defendants will look to have as much blame as possible assessed against each other, and especially against defendants who are immune or can't pay. Your goal, of course, is the opposite: To have as much fault for your injuries as possible assigned to defendants who have the resources to pay.

(Learn more about intervening and superseding causes for a personal injury.)

Failure to Diagnose or Treat a Condition

When your doctor negligently fails to diagnose or treat some condition, you might argue that the doctor's carelessness caused the condition to get worse or, worse still, caused your chance of recovery or survival to decrease. The doctor's response is likely to be that any delay in diagnosis or treatment didn't matter, because:

• your condition would have progressed and gotten worse regardless of when it was caught or treated, or
• your chances of recovery or survival wouldn't have improved with earlier diagnosis or treatment, because yours was an aggressive or progressive condition.

This might be called the "it would've happened anyway" defense.

Suppose, for instance, that you go to your doctor's office complaining of a persistent cough and chest pain. The doctor diagnoses you with pneumonia and prescribes an antibiotic. Your symptoms seem to improve just a bit, but eventually they return. Four months later you see another doctor, who diagnoses you with advanced lung cancer. Your chances of survival, you're told, are slim.

If you sue the first doctor for negligent failure to diagnose your cancer, the doctor's expert causation witness will testify that:

• your disease still would have been in an advanced state had it been diagnosed months earlier, and
• your chances of surviving that sort of advanced lung cancer were always extremely poor.

Get Help With Your Personal Injury Causation Problem

The fact that causation is rarely an issue doesn't mean you can forget about it. Proof of negligence and an injury, without more, means you lose your case. The defendant isn't likely to announce in advance that they intend to blow your case up for lack of causation. Chances are you won't find out you have causation problems until its too late.

You can bet that insurance company attorneys know causation, how it works, and most importantly, when its thin or absent. Without experienced legal help on your team, you'll quickly be in over your head. Make it a fair fight by hiring legal counsel to represent you.

When you're set to move forward with your case, here's how to find an attorney who's right for you.