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Evidence

Expert Witness

A witness allowed to give opinion testimony because specialized knowledge will help the factfinder understand evidence or decide facts.

Governing rule: Fed. R. Evid. 702

Plain-English definition

An expert witness can explain technical, scientific, medical, financial, engineering, or industry issues that ordinary jurors may not understand. The expert must be qualified, and the opinion must be reliable and helpful, not just impressive sounding.

How it works

Expert opinions are disclosed before trial. Opponents may depose the expert and file Daubert motions challenging qualifications, methods, data, or fit.

Why it matters

Expert testimony can convert complex records into a story the jury can understand, or it can be excluded and leave a party unable to prove an element.

Related terms

Daubert Motion
A pre-trial challenge to the admissibility of expert testimony, asking the court to act as gatekeeper over scientific or technical evidence.
Motion in Limine
A pretrial motion asking the court to admit, exclude, or limit specific evidence before the jury hears it.

More in Evidence

Attorney-Client Privilege
A protection for confidential communications between attorney and client made for the purpose of seeking or giving legal advice.
Authentication
The requirement to show that evidence is what the offering party claims it is.
Burden of Proof
The obligation to prove a claim, defense, or issue to the required legal standard.
Business Records Exception
A hearsay exception for records kept in the regular course of business under reliable recordkeeping conditions.
Clear and Convincing Evidence
A heightened proof standard requiring evidence stronger than preponderance but below beyond a reasonable doubt.
Daubert Motion
A pre-trial challenge to the admissibility of expert testimony, asking the court to act as gatekeeper over scientific or technical evidence.
Hearsay
An out-of-court statement offered to prove the truth of what the statement asserts.
Motion in Limine
A pretrial motion asking the court to admit, exclude, or limit specific evidence before the jury hears it.
Not legal advice. Definitions are for general reference. Consult an attorney before relying on any term in a real case.