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.
§ 2703.Bases of Opinion Testimony By Experts
Chapter 40: Oklahoma Evidence Code · Last amended November 1, 2002 · Last verified August 3, 2026
In one sentenceLets an expert base an opinion on facts or data perceived or learned before the hearing, admissible or not, if experts in the field reasonably rely on that type of information, while barring disclosure of otherwise-inadmissible facts to the jury unless their probative value substantially outweighs their prejudicial effect.
Full Text of § 2703
Amendment History
Added by Laws 1978, SB 276, c. 285, § 703, eff. 10/1/1978; Amended by Laws 2002, HB 1939, c. 468, §55, eff. 11/1/2002; Amended by Laws 2009, HB 1603, c. 228, §19, eff. 11/1/2009.
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Supreme Court in the case of Douglas v. Cox Retirement Properties, Inc., 2013 OK 37, 302 P.2d 789 (Okla. 2013) and repealed by Laws 2013, 1st Ex.Sess., c. 15, § 4.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
An expert doesn't need firsthand, admissible evidence for every fact behind an opinion. This section lets the expert draw on facts or data perceived at or before the hearing, and if that's the type of information experts in the field reasonably rely on, the underlying facts or data don't themselves have to be admissible for the opinion to come in.
That flexibility has a limit built around the jury. Facts or data that would otherwise be inadmissible can't be disclosed to the jury by the proponent of the opinion unless the court finds their probative value in helping the jury evaluate the expert's opinion substantially outweighs their prejudicial effect. A compiler's note explains that a 2009 amendment to this section was later held unconstitutional and repealed, so the balancing test in force today traces to the 2002 amendment.
Frequently Asked Questions
Does the information behind an expert's opinion have to be admissible evidence itself?
No, if it's of a type reasonably relied upon by experts in the particular field, it doesn't need to be independently admissible.
Can the jury hear about inadmissible facts an expert relied on?
Only if the court determines their probative value in assisting the jury to evaluate the expert's opinion substantially outweighs their prejudicial effect.
What happened to the 2009 amendment to this section?
A compiler's note explains it was held unconstitutional by the Oklahoma Supreme Court and repealed, so the section as currently written traces to the 2002 amendment.
Can an expert rely on facts perceived after the hearing already started?
The statute covers facts "perceived by or made known to the expert at or before the hearing" -- it doesn't address facts learned afterward.
Source & verification. Section text is reproduced verbatim from
Title 12 of the Oklahoma Statutes, enacted by the Oklahoma Legislature.
Last verified August 3, 2026.
· Official source
Also known as: basis of expert opinion oklahoma12 O.S. § 2703FRE 703 oklahoma equivalentinadmissible facts expert relied on oklahoma