“Proximate Causation” in California Personal Injury Claims

In tort law or personal injury law, “proximate causation” refers to the primary cause of an injury. In a personal injury lawsuit, you as the plaintiff can establish proximate cause by showing that your injury was sufficiently closely related to the defendant’s conduct that liability should attach.

Proximate cause is necessary to prove that another person was negligent for causing an injury.

Courts often use either a “but for” test or a “substantial factor” test to help determine whether or not a defendant’s conduct was the proximate cause of your injury. Courts also consider whether or not a defendant could have foreseen that their acts could have caused an injury. There is generally no proximate cause if there is no foreseeability.

Note that to establish negligence, you must prove that a defendant was both:

• the proximate cause of your injuries, and
• the actual cause of those injuries.

Actual cause is an easier concept to understand than proximate cause. Actual cause is simply the action that instigated an accident or injury.

Our California personal injury lawyers will highlight the following in this article:

• 1. What is proximate causation in a personal injury case?
  • 1.1. “But for” test
  • 1.2. “Substantial factor” test
• 2. Does the harm have to be foreseeable to create liability?
• 3. What happens when there are multiple causes of an accident?
• 4. What is actual cause?
• 5. What is the law in California?

1. What is proximate causation in a personal injury case?

In the context of personal injury law, a person’s actions are said to “proximately cause” your injury if your actions were a substantial factor in causing the injury.¹

You must show proximate cause in order to establish that a party was negligent in causing an accident. If a party was negligent, then you can sue that party and try to receive compensation for such things as:

• medical expenses,
• lost wages,
• property damage, and
• pain and suffering.

Example: John runs a red light and hits Sarah’s car. Sarah was legally driving and obeyed all traffic laws. Assume that Sarah suffered whiplash in the accident.

Here, John proximately caused the motor vehicle accident and Sarah’s injury. His failure to stop was a substantial factor in causing both the accident and the injury. Sarah could file a personal injury lawsuit against John on a negligence theory in order to receive damages for her whiplash.

Example: John runs a red light. Sarah swerves her car to avoid getting hit. She drives on, fuming because of John’s actions. She’s upset with her pulse racing. Three blocks later she hits a parked car and injures herself in the collision.

Here, while John may be a remote cause of the accident, he did not proximately cause Sarah’s injury. His running of the red light was not a substantial factor, or ultimate causation, in contributing to the injury.

Most jurisdictions use one of two tests to determine whether or not a person proximately caused an injury or accident. These are the:

• “but for” test, and
• “substantial factor” test.

1.1. “But for” test

According to the “but for” test, a court asks whether your injury would have occurred but for the defendant’s conduct, negligent act, or omission.

If the court finds that an injury would not have happened but for the defendant’s liability or negligent act, then there is proximate cause.

Example: Allen is driving the wrong way down the highway. Becky sees Allen and swerves to avoid being hit. She narrowly misses hitting Allen head on, but instead crashes into the guardrail, causing serious neck and back injuries.

Allen’s conduct of driving the wrong way on the highway is the “but for” cause of Becky’s injuries. If he had not been driving towards her, she would not have swerved, and she would not have crashed.

1.2. “Substantial factor” test

Some states use a “substantial factor” test to help determine whether or not a person’s conduct was the proximate cause of your injury.

Under this test, the court asks if the defendant’s acts or omissions were a substantial factor in the cause of the accident or cause of the injury.

If the answer is “yes,” then the defendant’s actions were the proximate cause of the accident/injury.

A substantial factor is one that contributes materially to the occurrence of an injury.

Sometimes an act is considered so disconnected to an accident or injury that a court cannot say that it was a substantial factor in causing that accident or injury.

Example: Ann wakes up 30 minutes late because her alarm clock did not go off because it was defective. Ann drives to work. Laura is driving alongside Ann on the highway but does not check her side view mirror and drives into Ann’s car. Ann loses control and suffers broken bones.

While Ann would have a personal injury claim against Laura, she could not sue the alarm clock company in a defective products lawsuit. The alarm clock’s failure to function properly was not a substantial factor in causing the accident with Laura.

When an act is disconnected to an accident, the law considers it outside the chain of events, or the chain of causation, leading up to the accident.

2. Does the harm have to be foreseeable to create liability?

Foreseeability is an important component of proximate cause.

Most jurisdictions say that a defendant’s acts are not the proximate cause of an accident unless the defendant could have foreseen that their acts or omissions would have resulted in the accident.

In some cases, an unforeseeable or intervening cause results in your injuries. In these cases, the defendant would typically not be liable to you since they reasonably could not have predicted the unlikely superseding cause. Superseding causes usually involve:

• acts of God,
• violations of criminal law by third parties, and
• intentional torts or wrongdoings.

Example: Aaron spills gasoline on the pavement while filling his car. Aaron does this in the midst of a thunderstorm.

A lightning bolt strikes the ground and causes the spilled gasoline to ignite. The fire burns Carol who is walking in the area.

Here, Aaron is not the proximate cause of Carol’s injuries. The lightning bolt is considered an act of God that was an unforeseeable and intervening cause of the injuries.

3. What happens when there are multiple causes of an accident?

If multiple people are responsible for causing an accident, then one of those people cannot avoid liability just because others contributed to the incident.

If a person’s actions were a proximate cause of the accident (in any way), then they will be held responsible for your damages.

When several people (for example, multiple drivers) cause your injuries, they will be held jointly and severally liable for your economic damages. Joint and several liability means that even though two or more people were determined to have caused someone’s injuries, you can collect the entire damage award from any one of them.

4. What is actual cause?

In order to successfully show that another party was negligent for your injuries, you must show that the defendant was both:

• the proximate cause of your injuries, and
• the actual cause of your injuries.

Actual cause is a much easier concept to grasp than proximate cause.

Actual cause is simply the action that instigated the accident. For example, if a car strikes a pedestrian, the driver’s actions constitute the actual cause of the accident.

In determining actual cause, courts generally do not have to analyze substantial factors or foreseeability issues.

“Actual cause” is sometimes referred to as “cause in fact” or “legal cause.”

5. What is the law in California?

California law generally follows the rules and issues discussed above.

If you file a negligence lawsuit against another person, you must prove both proximate and actual cause.

California law generally uses the substantial factor test in determining proximate cause.²

According to state law, a substantial factor in causing a type of harm is a factor that a reasonable person would consider to have contributed to the harm. It must be more than a remote or trivial factor. Further, it does not have to be the only cause of the harm.³

In California, you have to prove the following to successfully establish a defendant’s negligence:

1. the defendant owed you a duty of care,
2. the defendant breached such duty, and
3. the defendant’s negligence was both the proximate and actual cause of the harm to you.⁴

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