Sunday, December 28, 2025

The Law in Failure: The Eggshell Skull Doctrine and Constitutional Due Process

A White Paper on Tort Reform, Medical Causation, and the Fifth Amendment

Executive Summary

The eggshell skull doctrine—requiring tort defendants to “take the plaintiff as found” and bear full liability for unforeseeably severe injuries—has long been treated as a settled principle of American tort law. However, modern tort litigation, medical complexity, and constitutional jurisprudence expose a fundamental flaw in the doctrine: it permits arbitrary deprivations of property in violation of the Fifth Amendment’s Due Process Clause. By severing damages from foreseeability, proportionality, and reliable proof of medical causation, the doctrine transforms compensatory damages into a form of compelled insurance for plaintiffs’ preexisting defects. This white paper argues that constitutional due process requires reform or limitation of the doctrine.

I. Background: The Eggshell Skull Doctrine

The eggshell skull rule holds that once a defendant’s conduct is a cause-in-fact of injury, the defendant is liable for the full extent of harm, even if the plaintiff’s injuries are exacerbated by preexisting vulnerabilities. Vosburg v. Putney, 50 N.W. 403 (Wis. 1891); Restatement (Second) of Torts § 461 (1965). Historically, the doctrine was justified as a corrective justice principle designed to ensure full compensation.

II. Due Process and Civil Liability

The Fifth Amendment prohibits deprivation of property without due process of law. U.S. Const. amend. V. Civil tort judgments are subject to this constraint. Honda Motor Co. v. Oberg, 512 U.S. 415, 434 (1994). Due process requires:

A meaningful opportunity to be heard;
Rational, non-arbitrary standards; and
Proportionality between conduct and deprivation.
Mathews v. Eldridge, 424 U.S. 319, 333 (1976).

III. The Constitutional Defect: Loss of Foreseeability and Proportionality

Foreseeability is a cornerstone of tort law. Palsgraf v. Long Island R.R. Co., 248 N.Y. 339 (1928). The eggshell skull doctrine abandons foreseeability at the damages stage, exposing defendants to catastrophic liability untethered from culpability. This creates outcomes that are unpredictable and disproportionate, violating due process principles articulated in BMW of North America, Inc. v. Gore, 517 U.S. 559, 574–75 (1996).

IV. Forced Payment for Plaintiff Defects

The doctrine compels defendants to pay not merely for harm they caused, but for injuries magnified by the plaintiff’s age-related degeneration, genetic abnormalities, congenital illness, lifestyle choices, carelessness, fatigue, intoxication, or other preexisting impairments. These conditions—often inevitable or self-caused—are treated as legally indistinguishable from injuries actually caused by the defendant. This converts tort law into a system of involuntary loss-spreading, forcing private defendants to insure against another party’s biology and life history without fault or foreseeability.

V. Daubert, Medical Causation, and Evidentiary Failure

Under Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), courts must exclude speculative or unreliable expert testimony. Medical causation requires reliable proof that the defendant’s conduct was a substantial factor in producing the injury. General Electric Co. v. Joiner, 522 U.S. 136, 146 (1997); In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 742–43 (3d Cir. 1994).

The eggshell skull doctrine undermines Daubert by preemptively resolving causation questions as a matter of law, allowing experts to attribute the full scope of injury to defendants without reliably excluding alternative causes such as degeneration, intoxication, or behavioral risk factors. This evidentiary shortcut results in damages based on conjecture, violating due process. Holmes v. South Carolina, 547 U.S. 319, 324–25 (2006).

VI. Counterarguments and Rebuttals

A. “The Doctrine Is Settled Common Law”

Rebuttal: Longevity does not confer constitutional immunity. Courts have repeatedly reformed entrenched doctrines when they violate due process. Honda, 512 U.S. at 430–32; New York Times Co. v. Sullivan, 376 U.S. 254 (1964).

B. “It Affects Only Damages, Not Liability”

Rebuttal: Due process applies to damages as well as liability. Arbitrary or grossly disproportionate damages violate constitutional fairness. Gore, 517 U.S. at 574–75.

C. “Fairness Requires Full Compensation”

Rebuttal: Compensation cannot justify compelled subsidization. Forcing defendants to pay for harms caused by genetics, aging, intoxication, or carelessness exceeds compensation and becomes unconstitutional redistribution. Eastern Enterprises v. Apfel, 524 U.S. 498, 528–29 (1998) (plurality).

D. “Daubert Solves the Problem”

Rebuttal: The doctrine structurally disables meaningful Daubert scrutiny by converting disputed medical causation into a legal presumption. Joiner, 522 U.S. at 146.

E. “Limiting the Doctrine Invades the Jury’s Role”

Rebuttal: Due process exists to constrain arbitrary jury outcomes. Courts routinely limit jury discretion through evidentiary and constitutional review. Honda, 512 U.S. at 432.

VII. Reform Proposals

Constitutional Limitation: Prohibit application of the eggshell skull doctrine where damages are unforeseeable and disproportionate.
Enhanced Causation Proof: Require Daubert-compliant medical evidence distinguishing defendant-caused harm from preexisting conditions.
Proportional Damages Instructions: Mandate jury instructions separating aggravation caused by defendants from independent vulnerabilities.
Judicial Review: Require heightened post-verdict review for damages driven by preexisting conditions.

VIII. Conclusion

The eggshell skull doctrine, as currently applied, denies defendants a fair hearing, forecloses meaningful evidentiary challenges, and imposes arbitrary deprivations of property. Constitutional tort reform is not an attack on compensation, but a restoration of due process. The Fifth Amendment requires that tort liability be grounded in foreseeability, proportionality, and reliable proof—not legal fictions that compel defendants to insure against the accidents of another’s biology and life history.

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I. Model Statutory Language

(Constitutional Limitation on the Eggshell Skull Doctrine)

Section 1. Short Title

This Act shall be known as the Fair Causation and Proportional Liability Act.

Section 2. Legislative Findings and Purpose

The Legislature finds that:

Civil tort judgments constitute deprivations of property subject to constitutional due process.
Liability for damages must be based on reliable proof of causation and proportional responsibility.
The traditional “eggshell skull” doctrine, when applied without limitation, may impose damages disproportionate to a defendant’s fault and unsupported by reliable medical evidence.
Advances in medical science permit meaningful differentiation between harm caused by a defendant and harm attributable to preexisting conditions, degeneration, genetics, intoxication, fatigue, or other independent factors.

Purpose.
The purpose of this Act is to preserve full compensation for injuries actually caused by defendants while ensuring that damages awards comply with due process by requiring reliable proof of medical causation and proportional allocation of damages.

Section 3. Limitation on Liability for Preexisting Conditions

(a) A defendant shall be liable only for the aggravation of a preexisting condition that is proven, by a preponderance of the evidence, to have been caused by the defendant’s conduct.

(b) A defendant shall not be liable for:

Injury or impairment that would have occurred in the absence of the defendant’s conduct; or
The natural progression of age-related degeneration, genetic vulnerability, congenital conditions, disease, intoxication, fatigue, carelessness, or other independent factors not caused by the defendant.

Section 4. Evidentiary Requirements for Medical Causation

(a) Medical causation of damages shall be established by expert testimony that meets the requirements of Rule 702 of the Rules of Evidence and applicable reliability standards.

(b) Expert testimony must:

Identify the specific injury caused by the defendant;
Distinguish that injury from preexisting or independent conditions; and
Reliably explain the basis for attributing the claimed damages to the defendant rather than alternative causes.

Section 5. Proportional Damages

(a) Where injury results from a combination of defendant-caused harm and preexisting or independent conditions, damages shall be apportioned to reflect only the harm caused by the defendant.

(b) Failure to apportion damages where apportionment is reasonably possible shall constitute reversible error.

Section 6. Construction

Nothing in this Act shall be construed to:

Eliminate liability for injuries actually caused by defendants; or
Limit recovery where the defendant’s conduct is proven to be the predominant cause of the plaintiff’s injury.

II. Model Jury Instructions

(Fair Causation and Proportional Damages Instruction)

Instruction 1: Causation of Injury

You must determine whether the defendant’s conduct caused the plaintiff’s injury.

The defendant is responsible only for injuries that were actually caused by the defendant’s conduct. The defendant is not responsible for injuries caused by:

Preexisting medical conditions,
Age-related changes,
Genetic factors,
Disease,
Intoxication,
Fatigue,
Carelessness, or
Other conditions or events not caused by the defendant.

Instruction 2: Aggravation of Preexisting Conditions

If you find that the plaintiff had a preexisting condition, you may award damages only for the extent to which the defendant’s conduct aggravated that condition.

You may not award damages for:

The condition itself, or
Any worsening that would have occurred even without the defendant’s conduct.

Instruction 3: Medical Expert Testimony

In determining causation and damages, you must rely on medical expert testimony that is supported by reliable methods and evidence.

You should not accept an expert’s opinion if it:

Assumes causation without explanation,
Fails to consider alternative causes, or
Attributes all injury to the defendant without distinguishing preexisting or independent conditions.

Instruction 4: Proportional Damages

If you find that the plaintiff’s injuries were caused partly by the defendant and partly by other factors, you must award damages only in proportion to the harm caused by the defendant.

Damages must reflect:

What injury the defendant caused, and
The extent of that injury, and no more.

Instruction 5: Fairness and Constitutional Limits

Your verdict must be based on evidence and reasoned judgment. You may not impose damages as a form of punishment or as compensation for conditions the defendant did not cause.

III. Optional Appellate Preservation Clause (Bench Instruction)

“Failure to require reliable proof distinguishing defendant-caused injury from preexisting or independent conditions may result in a verdict that violates constitutional due process.”

David Behar, M.D., E.J.D.