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If you've been injured in an accident, the at-fault party's insurance company may try to argue that your injuries were caused by a pre-existing medical condition rather than the accident itself. This is one of the most common tactics insurers use to deny or reduce personal injury claims. But there's a well-established legal doctrine that protects you: the eggshell plaintiff rule. Below, our friends at Mitchell & Danoff Law Firm, Inc explain why pre-existing conditions don’t ruin your personal injury case.

What Is the Eggshell Plaintiff Rule?

The eggshell plaintiff rule — sometimes called the "eggshell skull rule" or the "thin skull rule" — is a legal doctrine that holds a defendant liable for the full extent of a plaintiff's injuries, even if those injuries are more severe than what a healthy person would have suffered in the same accident.

The name comes from a simple analogy. Imagine someone with a skull as fragile as an eggshell. If a defendant's negligence causes that person's skull to shatter, the defendant cannot argue that a person with a normal skull would not have been injured as badly. The defendant must "take the plaintiff as they find them."

This principle has been upheld in courts across the United States for well over a century. It applies in virtually every type of personal injury case, from car accidents and slip-and-fall incidents to medical malpractice and workplace injuries.

How the Eggshell Plaintiff Rule Works in Practice

Consider a real-world example. Suppose you have degenerative disc disease — a common condition, especially in adults over 40 — and you're rear-ended at a stoplight. The impact aggravates your spinal condition, causing herniated discs that require surgery.

Without the eggshell plaintiff rule, the insurance company might argue that your degenerative disc disease, not the accident, caused your herniated discs. With the rule in place, the negligent driver is responsible for the full extent of the harm they caused, including the aggravation of your pre-existing condition.

The key legal distinction is between a pre-existing condition and a new injury caused or worsened by someone else's negligence. The defendant does not get to choose their victim. If their carelessness injures someone who happens to be more vulnerable than average, they bear the consequences.

Pre-Existing Conditions That Commonly Come Up in Personal Injury Cases

Insurance adjusters frequently try to use pre-existing conditions as a shield against liability. Some of the most common conditions that arise in these disputes include arthritis and joint degeneration, prior back or neck injuries, osteoporosis, diabetes (which can slow healing), prior surgeries at the injury site, and mental health conditions like anxiety or PTSD.

In each of these situations, the eggshell plaintiff rule prevents the defendant from escaping liability simply because the plaintiff was not in perfect health before the accident.

What You Need to Prove

While the eggshell plaintiff rule protects your right to full compensation, you still need to demonstrate that the accident caused a genuine worsening of your condition. This typically involves several key elements.

First, you'll need medical records documenting your condition both before and after the accident. Second, professional medical testimony establishing how the accident aggravated your pre-existing condition is often critical. Third, evidence connecting the defendant's negligence to the specific worsening of your health must be presented.

An experienced personal injury lawyer will know how to obtain and present this evidence effectively, making it difficult for insurance companies to shift blame onto your medical history.

The Insurance Company's Playbook — and How to Counter It

Insurance adjusters are trained to look for pre-existing conditions in your medical records. Their strategy is straightforward: argue that your current pain and limitations existed before the accident and therefore are not the defendant's responsibility.

They may request access to years of your medical history, looking for any prior complaints of pain in the same body region. They may hire their own medical specialists to review your records and testify that the accident was not the cause of your current symptoms.

The eggshell plaintiff rule does not eliminate the need to fight these tactics. What it does is establish the legal framework in your favor. Your attorney can use this doctrine to argue that even if your spine, knee, or shoulder was not in perfect condition before the accident, the defendant is still responsible for making it worse.

Why This Matters for Your Case

If you have a pre-existing condition and you've been hurt in an accident, do not assume your claim is weak. The eggshell plaintiff rule exists precisely to ensure that vulnerable individuals receive fair compensation. Insurance companies count on claimants feeling discouraged by their medical history. Understanding your rights under this doctrine can be the difference between accepting a lowball settlement and receiving the full compensation you deserve.

Consult with a personal injury attorney who has experience handling cases involving pre-existing conditions. The right legal team will know how to document the aggravation of your condition, counter the insurance company's arguments, and ensure you are treated fairly under the law.