Eggshell plaintiff

What is the eggshell plaintiff rule?

The eggshell plaintiff rule holds that a defendant is responsible for the full extent of the harm they cause, even where an unusually vulnerable person suffered far more than an average person would have.

The name comes from the illustration of someone with a skull as fragile as an eggshell. A blow that would bruise most people proves catastrophic, and the person who struck them answers for the actual result.

The rationale is a choice about who bears the risk of an unknown vulnerability. The law places it on the party who acted carelessly rather than on the person who happened to be fragile.

It is sometimes called the thin skull rule, and both terms describe the same doctrine.

It is one of the oldest and most settled principles in injury law and appears in some form in nearly every jurisdiction.

What does the rule cover?

It reaches a broad range of vulnerabilities.

• Degenerative spinal changes that were previously asymptomatic
• Prior injuries to the same body region
• Osteoporosis and other conditions affecting bone strength
• Haemophilia and other bleeding disorders
• Psychological vulnerability that worsens the response to trauma
• Age related fragility in older claimants

Where does the rule stop?

It applies to the extent of harm rather than to whether harm was caused at all. The defendant must still have caused some injury.

It does not make a defendant responsible for a condition that would have deteriorated identically without the incident, which is why establishing the trajectory beforehand matters.

It is also distinct from apportionment. Where a prior condition contributes to the current state, the analysis separates aggravation from the underlying condition.

How does it work in practice?

Defendants rarely argue against the rule directly, because it is well settled. They argue causation instead, contending the current condition reflects natural progression.

The response is the same evidence that supports any aggravation claim, particularly prior imaging and records showing the absence of treatment beforehand.

A clear jury instruction on the rule matters, since jurors otherwise tend to discount a claim where the person was already vulnerable.

Explaining the rule plainly to a jury is often more effective than arguing it, since the underlying fairness is intuitive once stated.

Common questions

Does this mean my prior condition is irrelevant?

No. It remains relevant to establishing your baseline and to separating aggravation from the underlying condition. It simply does not reduce the defendant's responsibility for what they caused.

Does the rule apply to emotional injuries?

It has been applied to psychological vulnerability in appropriate circumstances, though these claims are analyzed carefully on their facts.

Is it the same as the thin skull rule?

Yes. The two terms describe the same doctrine and are used interchangeably.