Rule Text
The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence in order for the opinion or inference to be admitted. Facts or data that are otherwise inadmissible shall not be disclosed to the jury by the proponent of the opinion or inference unless the court determines that their probative value in assisting the jury to evaluate the expert's opinion substantially outweighs their prejudicial effect.
Amendment history: Added by Laws 1978, c. 285, § 703, eff. Oct. 1, 1978. Amended by Laws 2002, c. 468, § 55, eff. Nov. 1, 2002; Laws 2013, 1st Ex.Sess., c. 15, § 5; Laws 2013, 1st Ex.Sess., c. 15, § 6. NOTE: Laws 2009, c. 228, § 19 was held unconstitutional by the Oklahoma Supreme Court in the case of Douglas v. Cox Retirement Properties, Inc., 2013 OK 37, 302 P.2d 789 (Okla. 2013) and repealed by Laws 2013, 1st Ex.Sess., c. 15, § 4.
Plain-English Summary (for reference only — not a substitute for the rule text above)
This summary is not the rule. The rule text controls.
When an expert witness gives an opinion in court, that opinion has to be based on facts or information. This rule explains where those facts can come from. The expert can use things they saw or learned themselves, or information other people gave them before or during the case.
The information the expert relies on does not have to be the kind of evidence that would normally be allowed in court. As long as other experts in that same field would normally use that type of information to form opinions, it can support the expert's opinion here too. This lets experts work the way they normally would in their profession, even if some of the background information wouldn't be allowed as evidence on its own.
However, there is a limit. If the underlying facts or data would not normally be allowed as evidence, the side using the expert cannot just tell the jury about that information. The judge only allows it to be shared with the jury if it would help the jury understand the expert's opinion a lot more than it would unfairly influence them. In other words, the judge acts as a gatekeeper to make sure the jury isn't misled or unfairly swayed by information that wouldn't normally be considered reliable evidence.
