Under Rule 703, what is allowed about data underlying an expert opinion?

• A. Experts must rely only on admissible data.
• B. Data underlying opinions must be admitted as separate exhibits.
• C. Experts may base opinions on data not admissible if reasonably relied upon; data may be disclosed if the court requires.
• D. Data may not be disclosed under any circumstances.

Answer: (C)

Under Rule 703, an expert may base an opinion on facts or data in the case that the expert has been made aware of, even if those data would not be admissible as evidence. The crucial point is that the data must be of a type reasonably relied upon by experts in the field. The data themselves do not have to be admitted into evidence simply because the opinion is admissible. If the court determines that sharing the underlying data would help the jury evaluate the opinion, it may require disclosure of that data to the jury. In short, experts can rely on non-admissible data if it’s reasonably relied upon, and the court can require disclosure of the data to aid evaluation.