Which statement about the proper basis for an expert's opinion is true?

• A. An expert's personal knowledge is a proper basis.
• B. The expert may never rely on inadmissible evidence.
• C. An expert's opinion must be based solely on data admitted into evidence at trial.
• D. An expert may rely on inadmissible evidence (hearsay) commonly relied on by experts in the same field.

Answer: (A)

An expert can form an opinion based on personal knowledge. An expert’s own observations, experience, and specialized training are valid foundations for an opinion, not requiring the data to be admitted into evidence. This broad ability to rely on personal knowledge is a fundamental aspect of how experts present their opinions.

Why this is the best answer: It captures a universally permissible basis for expertise without imposing conditions about what must be admitted at trial or restricting reliance to only admissible information. While experts may also rely on data not admitted into evidence if they’re the type practitioners in the field would reasonably rely on, personal knowledge stands as a clear, always-acceptable foundation.

Briefly on the other statements: insisting that an expert may never rely on inadmissible evidence is too strict, since experts may rely on such information if it’s the kind commonly relied upon in the field. Requiring the opinion to be based solely on data admitted at trial is unnecessary and too limiting. The nuance about relying on inadmissible hearsay reflects the rule in specific contexts, but the most straightforward, universally valid basis remains the expert’s personal knowledge.