Cite as 2016 Ark. 157
evidence is admissible and therefore found the statute to be unconstitutional. The statute in Johnson provided as follows:
Any evidence of damages for the costs of any necessary medical care, treatment, or services received shall include only those costs actually paid by or on behalf of the plaintiff or which remain unpaid and for which the plaintiff or any third party shall be legally responsible.
2009 Ark. 241, at 10, 308 S.W.3d at 142 (emphasis in original) (quoting Ark. Code Ann. § 16-55-212(b) (Supp. 2003)).
In Johnson, we held that because the provision clearly limited the evidence that may be introduced relating to the value of medical expenses, thereby dictating what evidence is admissible, the statute violated the separation-of-powers doctrine. Johnson, 2009 Ark. 241, 308 S.W.3d 135. In the seat-belt statute, section 27-37-703(a), the trial court is given the discretion to determine whether evidence is admissible in product-liability actions only and is barred from determining admissibility in other actions.
Mendoza contends that section 27-37-703 is a matter of substantive law defining what is negligence for purposes of comparative fault. In support of her contention, Mendoza relies on Potts v. Benjamin, 882 F.2d 1320 (8th Cir. 1989), where the Eighth Circuit held that a statute modifying the content of state tort-law doctrines of contributory and comparative negligence was a classic example of "the type of substantive rule of law binding upon a federal court in a diversity case." Id. at 1324. In Potts, the Eighth Circuit addressed Arkansas Code Annotated section 27-34-106, the statute regarding the use of evidence of failure to place
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