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Impartiality Duty

Definition

The obligation on an expert witness to provide the same opinion regardless of which party instructed them. An expert who would change their conclusions if retained by the other side is not acting as an expert but as an advocate.

Applies to
Expert witnesses in any proceeding
Test
Would opinion change if instructed by the other side?
Violation result
Expert acts as advocate, not witness
Owed to
The court, not the instructing party

Common questions

Who does an expert witness's impartiality duty run to?+

The duty runs to the court or tribunal, not to the party who instructed and pays the expert, which is why many jurisdictions require experts to certify this obligation in writing.

What is a practical sign that an expert has breached impartiality?+

Selectively citing only the data that supports the instructing party's case, refusing to disclose contrary findings, or shifting conclusions based on which side asked the question are common red flags raised in cross-examination.

Related terms

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