16.2 Proximate Cause & Intervening Forces

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1 Introduction & FYLSE Examination Guide

1.1 FYLSE Exam Structure, Passing Standard & Administration 1.2 Study Method, Pacing & MBE-Style Technique

2 Contracts: Mutual Assent, Capacity & Contract Formation

2.1 The Offer & Objective Theory of Assent 2.2 Termination & Irrevocability of Offers 2.3 Acceptance & the Mailbox Rule 2.4 Mirror Image Rule & UCC 2-207 Battle of the Forms 2.5 Mistake in Contract Formation 2.6 Fraud, Duress, Undue Influence & Illegality 2.7 Capacity to Contract

3 Contracts: Consideration, Estoppel & Implied Obligations

3.1 Consideration & the Bargained-For Exchange 3.2 Past & Moral Consideration, Pre-Existing Duty & Modification 3.3 Promissory Estoppel & Detrimental Reliance 3.4 Implied-in-Fact Contracts & Quasi-Contract 3.5 Implied Covenant of Good Faith, Fair Dealing & Indefinite Terms

4 Contracts: Third-Party Beneficiaries, Assignment & Delegation

4.1 Third-Party Beneficiary Contracts 4.2 Assignment of Rights 4.3 Delegation of Duties

5 Contracts: Statute of Frauds, Parol Evidence & Interpretation

5.1 Statute of Frauds: Contracts Within the Statute 5.2 Satisfying the Statute: Writing, Signature & Exceptions 5.3 The Parol Evidence Rule 5.4 Contract Interpretation & Canons of Construction

6 Contracts: Performance, Conditions, UCC Warranties & Breach

6.1 Conditions: Express, Constructive & Excuse 6.2 Substantial Performance vs. Perfect Tender 6.3 Cure, Rejection, Revocation & Installment Contracts 6.4 UCC Article 2 Warranties & Risk of Loss 6.5 Anticipatory Repudiation & Insecurity

7 Contracts: Remedies, Discharge & Changed Circumstances

7.1 Expectation Damages & Their Limitations 7.2 Reliance, Restitution & Liquidated Damages 7.3 Specific Performance & Injunctive Relief 7.4 UCC Article 2 Buyer's and Seller's Remedies 7.5 Impossibility, Impracticability & Frustration of Purpose 7.6 Discharge by Agreement: Rescission, Novation & Accord and Satisfaction

8 Criminal Law: Principles of Criminal Liability & Mens Rea

8.1 Actus Reus, Voluntary Acts & Omissions 8.2 Criminal Causation & Intervening Causes 8.3 Common Law & Model Penal Code Mens Rea 8.4 Mistake of Fact, Mistake of Law & Concurrence

9 Criminal Law: Inchoate Offenses & Accomplice Liability

9.1 Criminal Attempt & Impossibility 9.2 Solicitation & the Merger Doctrine 9.3 Conspiracy & Merger Doctrine 9.4 Accomplice Liability: Actus Reus & Mens Rea 9.5 Scope of Accomplice Liability, Withdrawal & Parties to Crime

10 Criminal Law: Homicide & Crimes Against the Person

10.1 Common Law Murder & Malice Aforethought 10.2 Degrees of Murder, Premeditation & Deliberation 10.3 The Felony Murder Rule & Its Limitations 10.4 Voluntary & Involuntary Manslaughter 10.5 Non-Homicide Crimes Against the Person

11 Criminal Law: Property Crimes, Theft & Habitation

11.1 Common Law Larceny 11.2 Embezzlement & False Pretenses 11.3 Robbery & Extortion 11.4 Receiving Stolen Property 11.5 Burglary 11.6 Arson

12 Criminal Law: Defenses: Capacity, Justification & Excuse

12.1 Insanity: The Four Legal Tests 12.2 Intoxication, Diminished Capacity & Infancy 12.3 Self-Defense & Defense of Others 12.4 Defense of Property, Habitation & Law Enforcement Privileges 12.5 Duress & Necessity 12.6 Entrapment & Mistake as an Excuse

13 Torts: Intentional Torts to Persons & Property

13.1 Intent, Motive & Incapacity in Intentional Torts 13.2 Transferred Intent 13.3 Battery & Assault 13.4 False Imprisonment 13.5 Trespass to Land 13.6 Trespass to Chattels & Conversion

14 Torts: Privileges & Defenses to Intentional Torts

14.1 Consent: Express, Implied & Capacity 14.2 Exceeding & Vitiating Consent 14.3 Self-Defense & Defense of Others (Tort) 14.4 Defense of Property & Recapture of Chattels 14.5 Public & Private Necessity 14.6 The Shopkeeper's Privilege

15 Torts: Negligence — Duty of Care & Breach

15.1 Duty of Care & the Foreseeable Plaintiff 15.2 Affirmative Duties to Act & Special Relationships 15.3 Standard of Care: The Reasonable Person & Children 15.4 Professional Negligence, Informed Consent & Negligence Per Se 15.5 Land Possessor Liability & Premises Duties 15.6 Breach of Duty & Res Ipsa Loquitur

16 Torts: Causation, Defenses, Multiple Tortfeasors, Wrongful Death & Damages

16.1 Cause in Fact & Multiple Actors 16.2 Proximate Cause & Intervening Forces 16.3 Contributory, Comparative Negligence & Assumption of Risk 16.4 Joint and Several Liability, Contribution & Indemnity 16.5 Vicarious Liability & Non-Delegable Duties 16.6 Wrongful Death & Survival Actions 16.7 Statute of Limitations & Claim Accrual 16.8 Tort Damages: Compensatory, Nominal, Punitive & Mitigation

17 Torts: Strict Liability & Products Liability

17.1 Strict Liability for Animals 17.2 Abnormally Dangerous Activities & Scope of Risk 17.3 Strict Products Liability & Defect Categories 17.4 Products Liability Under Negligence, Warranty & Misrepresentation 17.5 Defenses to Products Liability

18 Torts: Emotional Distress, Defamation, Privacy & Economic Torts

18.1 Intentional Infliction of Emotional Distress 18.2 Negligent Infliction of Emotional Distress 18.3 Common Law Defamation: Elements, Libel & Slander 18.4 Constitutional Limits, Privileges & Defenses to Defamation 18.5 Invasion of Privacy 18.6 Nuisance & Economic Torts

16.2 Proximate Cause & Intervening Forces

Key Takeaways Explain This Topic AI

Proximate cause limits liability to harms within the scope of the foreseeable risk created by the defendant's negligence.

Under the eggshell-skull rule the defendant takes the plaintiff as found and is liable for the full extent of harm even where a pre-existing condition made it far greater than foreseeable.

A dependent intervening force is a normal response to the situation the defendant created, such as rescue, medical negligence, or subsequent disease, and does not break the causal chain.

An independent intervening force is unrelated to the defendant's conduct and supersedes only if it was unforeseeable.

Criminal acts and intentional torts of third parties are generally superseding unless the defendant's negligence created the very risk of that conduct, and unforeseeable acts of God are the other classic superseding cause.

Last updated: September 2026

• Proximate Cause & Intervening Forces
• 1. Proximate Cause: The Scope of Foreseeable Risk

Proximate cause (legal cause) evaluates whether the physical harm suffered by the plaintiff was a reasonably foreseeable result of the defendant's negligent breach. Defendant's Negligent Breach

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• ├── Foreseeable Type of Harm (Within Scope of Created Risk) ──▶ Proximate Cause Satisfied
• └── Highly Unforeseeable / Bizarre Type of Harm ──▶ No Proximate Cause (Wagon Mound)
• The Wagon Mound Rule: Foreseeability of the Harm

In the landmark decision Overseas Tankship (U.K.) Ltd. v. Morts Dock & Engineering Co., Ltd. ( The Wagon Mound No. 1 , 1961), the Privy Council repudiated the archaic direct-consequences rule of In re Polemis (which held a defendant liable for all direct physical results, however bizarre). Under the modern rule adopted across American jurisdictions:

The Rule of Law: An actor is liable only for harm that is within the scope of the foreseeable risks generated by the actor's negligent conduct.

Application in Wagon Mound: A ship negligently discharged furnace bunkering oil into Sydney Harbour. The oil drifted across the bay and coated the plaintiff's timber wharf. Two days later, molten metal dropped from welding operations onto floating cotton waste, igniting the oil and burning down the wharf. Scientific experts agreed that bunkering oil on water was not reasonably foreseeable to ignite. The court held that while fouling the slipways with oil was foreseeable, destruction by fire was an unforeseeable type of risk; therefore, proximate cause was lacking as a matter of law.

The Triad of Foreseeability: Type vs. Manner vs. Extent

To master proximate cause on the FYLSE, examinees must categorize foreseeability into three distinct dimensions: Foreseeability Triad

• ├── 1. TYPE of Harm ──▶ MUST be reasonably foreseeable (Wagon Mound)
• ├── 2. MANNER of Harm ──▶ Need NOT be foreseeable (Bizarre mechanism irrelevant)
• └── 3. EXTENT of Harm ──▶ Need NOT be foreseeable (Eggshell Skull Rule)

Dimension Foreseeability Requirement Doctrinal Rule & Application

Type of Harm MANDATORY The general category of injury (e.g., impact, burn, fall) must be foreseeable. If an actor carelessly stores gasoline in an unventilated basement, fire or explosion is foreseeable; poisoning from an unknown dormant fungus is not.

Manner / Mechanism of Harm IRRELEVANT If the type of harm is foreseeable, the fact that it occurred through an extraordinary, freakish, or bizarre sequence of events does not shield the defendant from liability ( Kinsman Transit Co. ).

Extent of Harm IRRELEVANT Once a foreseeable type of physical harm occurs, the defendant is liable for the full physical magnitude of the injury, even if catastrophic and unforeseeable ( Eggshell Skull Rule ).

Illustrative Scenario (Manner of Harm): A city worker negligently leaves an open, unguarded 10-foot manhole in a public sidewalk. A pedestrian carrying a box of kerosene lamps trips on the curb, drops the lamps into the hole, and the shattered kerosene lamp hits an exposed electrical cable, generating an explosive fireball that launches the pedestrian into the air. The city argues that an exploding fireball is an unforeseeable manner of injury from an open manhole. The argument fails: falling and suffering severe physical trauma is the foreseeable type of risk created by leaving an open manhole; the freakish sequence of ignition does not break proximate cause.

2. The Eggshell Skull (Thin Skull) Rule

A universal, ironclad fixture of tort law is the Eggshell Skull Rule (also known as the Thin Skull Doctrine or Talem Qualem Rule ): Defendant Negligently Commits Minor Physical Impact

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• Plaintiff Possesses Latent Pre-Existing Frailty (Hemophilia, Brittle Bones, Aneurysm)
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• Catastrophic, Disproportionate Injury or Death Results
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• RULE: Defendant Takes Plaintiff as Found ──▶ FULLY LIABLE FOR ALL DAMAGES
• The Rule of Law

The defendant takes the plaintiff as the defendant finds the plaintiff. If a defendant commits a negligent act that inflicts foreseeable physical impact or bodily injury upon the plaintiff, the defendant is legally liable for all resulting physical consequences , no matter how severe, unexpected, or extraordinary, and regardless of whether the magnitude of harm was foreseeable.

Application to Pre-Existing Medical Conditions:

If Driver negligently rear-ends Pedestrian at 5 mph—an impact that would leave an ordinary person with a minor bruise—but Pedestrian suffers from severe latent osteoporosis or hemophilia, causing extensive internal hemorrhage, permanent paralysis, or death, Driver is liable for 100% of the catastrophic medical expenses and wrongful death damages.

Latent vulnerabilities include: hemophilia, latent heart disease, dormant cancer triggered by trauma, brittle bone disease ( osteogenesis imperfecta ), and pre-existing psychiatric fragility.

Scope and Limitations:

The eggshell skull rule applies strictly to physical bodily injuries .

It does not apply to create initial duty or proximate cause for pure emotional distress (NIED) where a bizarre, unusually sensitive bystander suffers severe shock from conduct that would not distress a person of normal sensibilities.

Once a physical impact/injury occurs, the eggshell skull rule applies with full force to all physical and subsequent psychological sequelae.

3. Intervening Forces: Dependent vs. Independent & Superseding Causes

When evaluating indirect causation, an intervening force is an external force of nature or action of a third party that enters the sequence of events after the defendant has committed the breach. Intervening forces are divided into two fundamental categories: Intervening Forces

• ├── Dependent Intervening Forces (Foreseeable Responses) ──▶ DO NOT SEVER LIABILITY (D remains liable)
• │ ├── Ordinary Medical Malpractice (Doctor casts broken leg improperly)
• │ ├── Rescuer Intervention ("Danger invites rescue" - Rescuer injured or acts)
• │ ├── Reflexive / Instinctive Reactions (Crowd flees in sudden panic)
• │ └── Weakened Condition Complication (Patient on crutches slips and falls)
• └── Independent Superseding Causes (Highly Extraordinary Forces) ──▶ BREAK CAUSAL CHAIN (D relieved)
• ├── Gross Medical Malpractice / Reckless Treatment (Surgeon operates intoxicated)
• ├── Unforeseeable Intentional Crimes / Torts of Third Parties (Arsonist sets fire)
• └── Extraordinary Acts of God / Natural Catastrophes (Unprecedented 500-year deluge)
• Dependent Intervening Forces (Defendant Remains Liable)

A dependent intervening force is a normal, natural, or foreseeable response to the dangerous situation created by the defendant's negligence. Because these responses flow predictably from the initial peril, dependent forces DO NOT break the causal chain :

Subsequent Ordinary Medical Malpractice (The #1 FYLSE Trap): If a defendant's negligence causes physical injury requiring medical treatment, it is foreseeable as a matter of law that medical personnel may commit ordinary negligence during treatment. The original tortfeasor is liable for the initial injury AND the aggravated harm caused by the doctor's ordinary malpractice.

Rescuer Intervention ("Danger Invites Rescue"): Under Wagner v. International Ry. Co. , it is foreseeable as a matter of law that third parties will attempt to rescue someone placed in peril by the defendant. The original tortfeasor is liable for injuries suffered by the rescuer, and for ordinary negligence committed by the rescuer that accidentally aggravates the victim's harm.

Instinctive & Escape Reactions: When an actor creates a sudden peril, reflexive human escape reactions ( Scott v. Shepherd squib case) are foreseeable dependent forces; the original wrongdoer remains the proximate cause of resulting injuries.

Secondary Injuries & Weakened Physical Condition: If an injured plaintiff suffers a secondary injury due to their weakened condition (e.g., an accident victim using crutches slips on a clean floor because of impaired balance, fracturing a wrist), the original tortfeasor is liable for the secondary fracture.

Independent Superseding Causes (Severing Liability)

An independent intervening force operates independently of the situation created by the defendant. When an intervening force is so highly extraordinary, bizarre, and unforeseeable that the law deems it unfair to hold the original defendant liable, it is classified as a superseding cause :

Gross Medical Malpractice: While ordinary medical negligence is a dependent intervening force, gross medical malpractice, reckless conduct, or intentional medical abuse is an independent superseding cause that cuts off the original tortfeasor's liability for subsequent death or catastrophic worsening.

Unforeseeable Intentional Criminal Acts: Baseline rule: intentional criminal conduct and intentional torts of third parties are superseding causes.

The Foreseeable Crime Exception ( Restatement (Second) of Torts § 448 ): An intentional criminal act DOES NOT supersede liability if the very risk of that criminal conduct was what made the defendant's act negligent in the first place (e.g., a landlord failing to fix a broken security door in a high-crime apartment building where armed robberies are frequent).

Extraordinary Acts of God: While ordinary seasonal weather (rain, snow, ice, wind) is foreseeable and does not break causation, an extraordinary, unprecedented natural catastrophe (an 8.5 Richter earthquake or 500-year flood) operates as a superseding cause.

4. Master Comparison Matrix: Causation Doctrines

Doctrine Core Legal Standard Triggering Factual Paradigm Procedural Effect / Outcome Landmark Authority

"But-For" Test Sine qua non: harm would not occur without breach. Single tortfeasor or concurrent necessary causes. Actual cause established; plaintiff bears burden by preponderance. Standard common law rule

Substantial Factor Breach was an active, substantial contributing force. Concurrent independent sufficient causes (merging fires/toxins). Discards but-for test; all sufficient forces treated as actual causes. Kingston v. Chicago & N.W. Ry. (Wis. 1927)

Alternative Liability Multiple negligent actors; only one caused harm; unknown which. Simultaneous negligent shooting or identical contemporaneous risk. Burden of proof shifts to defendants to exonerate themselves. Summers v. Tice (Cal. 1948)

Market Share Liability Joinder of substantial share of generic fungible market. Mass exposure to identical chemical formula (DES). Several liability proportional to market share percentage . Sindell v. Abbott Laboratories (Cal. 1980)

Wagon Mound Foreseeability Scope of foreseeable risk governs proximate cause. Unusual sequence or unexpected category of damage. Harm must be of a foreseeable type ; manner and extent irrelevant. The Wagon Mound No. 1 (1961)

Eggshell Skull Rule Defendant takes plaintiff as found ( talem qualem ). Plaintiff possesses latent frailty (hemophilia, thin skull). Defendant liable for full physical extent of injuries. Universal common law rule

Dependent Intervening Force Normal, foreseeable response to created peril. Ordinary medical malpractice, rescuer aid, escape panic. Does not break causation ; original defendant remains liable. Wagner v. International Ry.

Superseding Cause Highly extraordinary, unforeseeable outside force. Gross malpractice, unforeseeable crime, catastrophic Act of God. Breaks causal chain ; relieves original defendant of subsequent harm. Restatement § 442 / § 448