Learning Outcomes
After reading this article, you will be able to identify and apply the rules of causation in tort law for MBE purposes. You will distinguish between factual causation ("but for" and substantial factor tests), proximate cause, and the treatment of multiple or indeterminate causes. You will also recognize common exam pitfalls and confidently answer MBE questions involving causation.
MBE Syllabus
For MBE, you are required to understand the principles governing causation in tort law. This includes both factual and legal causation, as well as how causation is handled in cases with multiple defendants or indeterminate causes. You should be able to:
- Apply the "but for" test and substantial factor test for factual causation.
- Analyze proximate (legal) cause, including foreseeability and intervening/superseding causes.
- Address causation issues in cases involving multiple or indeterminate defendants.
- Recognize the "eggshell plaintiff" rule and its effect on damages.
- Identify when causation is not established and common exam traps.
Test Your Knowledge
Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.
-
Which of the following best describes the "but for" test in tort causation?
- The defendant's act must be the only cause of the harm.
- The harm would not have occurred but for the defendant's act.
- The defendant's act must be the direct cause of the harm.
- The defendant's act must be the most important cause of the harm.
-
In a case with two fires, each sufficient to destroy a house, both started by different defendants, what test is most appropriate to establish causation?
- But for test
- Substantial factor test
- Proximate cause test
- Foreseeability test
-
Which of the following is most likely a superseding cause that breaks the chain of proximate causation?
- Negligent medical treatment after the initial injury
- A foreseeable rescue attempt
- An unforeseeable criminal act by a third party
- The plaintiff's own contributory negligence
-
Under the "eggshell plaintiff" rule, a defendant:
- Is liable only for foreseeable injuries
- Is liable for all injuries, even if the extent is unforeseeable
- Is not liable if the plaintiff had a pre-existing condition
- Is liable only for physical injuries
Introduction
Causation is a core requirement in tort law. To recover for negligence or other torts, a plaintiff must prove that the defendant's conduct caused the harm. Causation has two distinct elements: factual causation (did the defendant's act actually cause the harm?) and proximate (legal) causation (is the harm closely enough related to the defendant's act to justify liability?). The MBE tests both elements, often in scenarios involving multiple causes or intervening acts.
Factual Causation: The "But For" and Substantial Factor Tests
The first step is to determine whether the defendant's conduct was a factual cause of the plaintiff's harm.
But For Test:
Ask: Would the harm have occurred but for the defendant's act? If the answer is no, factual causation is established.
Key Term: But For Test A test for factual causation asking whether the harm would have occurred in the absence of the defendant's conduct.
In cases with multiple sufficient causes (e.g., two fires, each able to destroy a house), the "but for" test may not work. Instead, courts use the substantial factor test.
Key Term: Substantial Factor Test A test for factual causation used when multiple acts combine to cause harm, holding a defendant liable if their conduct was a substantial factor in bringing about the harm.
Proximate (Legal) Cause: Foreseeability and Intervening Causes
Even if factual causation is present, the defendant is only liable if the harm is a proximate result of their conduct. The key question is whether the type of harm was a foreseeable result of the defendant's act.
Key Term: Proximate Cause The legal limitation on liability, requiring that the harm be a foreseeable result of the defendant's conduct.
Intervening and Superseding Causes
Sometimes, another event occurs after the defendant's act and contributes to the harm. If the intervening event is foreseeable, the defendant remains liable. If it is unforeseeable and extraordinary (e.g., a criminal act by a third party), it may be a superseding cause that breaks the chain of causation.
Key Term: Superseding Cause An unforeseeable intervening event that breaks the chain of proximate causation, relieving the defendant of liability for subsequent harm.
Multiple and Indeterminate Causes
When more than one defendant may have caused the harm, and it is unclear whose act was responsible, courts may shift the burden of proof to the defendants (alternative causes approach) or hold all responsible if each was a substantial factor (substantial factor test).
Key Term: Alternative Causes Approach A method where, if multiple defendants acted negligently but only one caused the harm, the burden shifts to each defendant to prove they were not the cause.
The Eggshell Plaintiff Rule
A defendant takes the plaintiff as they find them. If the plaintiff has a pre-existing vulnerability, the defendant is liable for the full extent of the harm, even if it is greater than a typical person would suffer.
Key Term: Eggshell Plaintiff Rule The principle that a defendant is liable for all harm caused, even if the extent of injury is unforeseeable due to the plaintiff's pre-existing condition.
Worked Example 1.1
A driver negligently runs a red light and hits a pedestrian. The pedestrian suffers a broken leg, and due to a rare bone disease, the injury leads to permanent disability. Is the driver liable for the full extent of the harm?
Answer: Yes. Under the eggshell plaintiff rule, the driver is liable for all consequences, even if the extent of the injury was unforeseeable.
Worked Example 1.2
Two factories negligently start separate fires. Each fire alone would have destroyed a nearby house. The fires merge and the house is destroyed. Can both factories be held liable?
Answer: Yes. The substantial factor test applies. Each factory's conduct was a substantial factor in causing the harm, so both are liable.
Worked Example 1.3
A defendant injures a plaintiff, who is then given negligent medical treatment, making the injury worse. Is the defendant liable for the aggravated harm?
Answer: Yes. Negligent medical treatment is a foreseeable intervening cause, so the original defendant remains liable for the full harm.
Exam Warning
On the MBE, do not confuse factual causation with proximate cause. Even if the defendant's act was a factual cause, liability may be cut off if the harm was not foreseeable or if a superseding cause intervened.
Revision Tip
When analyzing causation, always ask: (1) Would the harm have occurred but for the defendant's act? (2) Was the harm a foreseeable result, or was there a superseding cause?
Key Point Checklist
This article has covered the following key knowledge points:
- Causation in tort law requires both factual and proximate cause.
- The "but for" test is used for factual causation; the substantial factor test applies in multiple sufficient cause cases.
- Proximate cause limits liability to foreseeable harms; unforeseeable superseding causes break the chain.
- The alternative causes approach shifts the burden to defendants in indeterminate cause cases.
- The eggshell plaintiff rule makes defendants liable for all harm, even if the extent is unforeseeable.
- Negligent rescue or medical treatment is usually a foreseeable intervening cause; criminal acts by third parties are often superseding causes.
Key Terms and Concepts
- But For Test
- Substantial Factor Test
- Proximate Cause
- Superseding Cause
- Alternative Causes Approach
- Eggshell Plaintiff Rule
