The Honorable Robert R. Beezer, United States Circuit Judge 1 for the Ninth Circuit, sitting by designation. 

## United States Court of Appeals

FOR THE EIGHTH CIRCUIT

___________ No. 96-3605

___________ * Air Evac EMS, Inc. * * Appellee, * * Appeal from the United States v. * District Court for the Western * District of Missouri Aeronautical Accessories, * Inc., Edwards & Associates, * [UNPUBLISHED] Inc., * * Appellants. *

_____________ Submitted: June 13,1997 Filed: September 5,1997

______________ Before RICHARD S. ARNOLD, Chief Judge, BEEZER and WOLLMAN, 1 Circuit Judges

_____________ BEEZER, Circuit Judge:
Defendants Aeronautical Accessories, Inc. (“Aeronautical”) a nd Edwards & Associates, Inc. (“E dwards”) appeal the district court’s jury verdict in favor of plaintiff Air Evac EMS (“Air Evac”) in Air Evac’s product liability actio n. We have jurisdiction pursuant to 28 U.S.C. § 1291. We affirm in part and reverse and remand i n part.2 I

This product liability action arises from a helicopte r accident. Early in the morning on April 1, 1988, pilot Davi d Short, flying a Bell helicopter to an accident scene, decided t o abort the mission due to weather conditions. The helicopter wa s equippedwith a “nightscanner” light, a rotating search ligh t mounte dunderneath the helicopter. When Short activated th e nig htscanner in order to check his forward visibility, the glar e from the light temporarily blinded him. He attempted to turn off the nightscanner, but the light failed to extinguish, causin g Short to lose visual reference to the ground. Short then lost con trol of the he licopter and it crashed into a field near Springfield , Missouri. Short and his passengers sustained injuries.

The ow ner of the helicopter, Air Evac, brought this actio n ag ainst Edwards, the installer of the nightscanner system, an d Aeronautical, a previous ownerof the helicopter, along with other defendants who have since been dismissed. The jury returned a verdict in favor of Air Evac, holding that Short was ten per cent at fault and the defendants ninety percent at fault. The distric t court awarded Air Evac $1,076,323.36 plus pre-judgment and post

judgment interest. The court denied the defendants’ motion t o alter or amend the judgment. This timely appeal followed.

II

De fendants first argue that the district court abused it s discretion in admitting the te stimony of Air Evac’s expert witness Michael Postiglione. See Peitzmeier v. Hennessy Indus., Inc. , 97 F.3d 2 93, 296 (8th Cir. 1996) (reviewing admission of exper t testimony for abuse of discretion). Defendants contend that3

Po stiglione's testimony is inadmissible under Daubert v. Merrel l Dow Pharmaceuticals, Inc. , 509 U.S. 579 (1993).
Postiglione testified that he found visual evidence that the contact points on the relay of the nightscanner had welded; other exp erts testified that they could not detect evidence of weldin g either through visual observation or with the use of a scannin g electron microscope. If such welding occurred, it would cause the light to remain illuminated even after the pilot moved the switch into the "off" position.
Defendants allege that Postiglione’s testimony is inadmissib le because he based his conclusio n on visual inspection alone, rather thanemploying other methods of inspection as did the othe r experts. But weakness in the factual basis of expert testimon y goes to the weight, and not the admissibility, of that testimony. Lo udermill v. Dow Chem. Co. , 863 F.2d 566, 570 (8th Cir. 1988 ) ("[a]s a general rule, the factual basis of an expert opini on goes to the credibility of the test imony, not the admissibility, and it is up to the opposing party to examine the factual basis for th e opinion in cross-examination"); see also Fed. R. Evid. 703. “Only if an expert's opinion is so f undamentally unsupported that it can offer no assistance to the jury must such testimony be excluded.” Hose v. Chicago Northwestern Transp. Co. , 70 F.3d 968, 974 (8t h Cir. 1995) (internal quotation omitted). The district court addressed the admissibility o f Post iglione's testimony in its denial of defendants' motion fo r summary judgment. The court noted that Postiglione's opinion was not solely based upon visual i nspection but also upon his analysis of the testimony of others and his experience with electrica l compon ents and relays. Further, we note that the defendant s pre sentedno evidence that the general practice of inspecting a n electrical relay for malfuncti on excludes visual observation. The4

district court did not abuse its discretion in admitting the expert testimony; it was the jury’s province to weigh the credibility of Postiglione’s testimony.

III

Defendants next argue that the district court abused it s discretion in admitting evidence of the failures of nightscanners that contained relays differen t from the relay in the nightscanner at issue. We review the district court's ruling on admissibility of evidence for an abuse of di scretion. United States v. Mendoza , 85 F.3d 1347, 1351 (8th Cir. 1996).

Apr imary evidentiary issue at trial concerned whether th e rela yin the nightscanner could accommodate the in-rush curren t passing through it without cau sing the light to remain illuminated after the unit was switched into the "off" position. Th e nightscanner at issue was a Symbolic Display assembly, containing a mechanical, 60-amp relay, labeled an “MB3D” relay. Defendants'
ex pert testified that this relay could accommodate the in-rus h current. The district court allowed Air Evac to introduce e vidence
con cerning the failure of nightscanners which used Glare-Ba n assemblies. Glare-Ban assemblies contain printed circuit contact 70 -amp relays. The evidence established that Symbolic Displa y assemblies and Glare-Ban assem blies are interchangeable, and thus, are subject to the same in-rush current. Because Glare-Ban and Symbolic Display assemblies contai n different relays, the defendants argue that the evidence relating to failures of nightscanners containing Glare-Ban assemblies is not substantially similar to the evidence concerning the failure of the nightscanner used by Air Evac. See McKnight v. Johnson Controls, Inc ., 36 F.3d 1396, 1410 (8th Cir. 1994) (evidence of othe r accidents is admissible only if the other accident is substa ntially5

similar to the accident at issue). As the district court noted , ho wever, the evidence of the failures of the Glare-Ba n nightscanners was relevant bot h: (1) to impeach the testimony that the 60-amp relay could handle the in-rush current and (2) t o establ ishthat the defendants' engineer was negligent in no t ade quatelytesting the MB3D relay to ensure it could accommodat e the in-rush current before ins talling that relay into the Symbolic Displa ys nightscanner. The district court did not abuse it s discretion in admitting the ev idence concerning the failure of the Glare-Ban nightscanners.

IV

Defend ants also assert that the district court erred i n admitting evidence of the fail ures of three other Symbolic Display nigh tscanners which contained MB3D relays. Defendants offer n o argument supporting this claim other than stating that the f ailures
we re too remote in time to be of probative value. Defendants ’ argument can be characterized as a claim that the evidence should not have been permitted under Federal Rule of Evidence 403. Under this r ule, a District Court is permitted to exclude relevan t evidence "if its probative value is substantially outweighedby the danger of unfair prejudice, co nfusion of the issues, or misleading the jury, or by considerations of undue delay [or] waste of time." Fed. R. Evid. 403. We will not reverse a district court' s determination respecting the admissibility of evidence under Rule 403 absent a clear and prejudicial abuse of discretion
. Intern ational Travel Arrangers v. NWA, Inc. 991 F.2d 1389, 140 0 (8th Cir. 1993). Alth oughthe subsequent failures of other Symbolic Displa y nightscanners occurred between five and eight years after the Air Evac accident, the district court found that the subsequen t failures were substantially similar to the failure of the6

nights canner used by Air Evac, and, thus the evidence ha d significant probative value. For example, the other Symboli c Display nightscanners that subsequently failed had configurations
an dmodifications identical to the nightscanner at issue
. Moreover, evidence was presented that on each failed Symboli c Display nightscanner the light tended to remain illuminated after being turned into the “off” po sition. Evidence of other accidents
can be used to prove causation. McKnight , 36 F.3d at 1410. Th e district court did not abuse its discretion.

V

Ne xt, defendants contend that the district court erred i n giving the jury a "negligent failure to warn" instruction. W e rev iewjury instructions for abuse of discretion. Karcher v
. Emerson Elec. Co. , 94 F.3d 502 , 510 (8th Cir. 1996), cert. denied , 117 S. Ct. 1693 (1997). Under Missouri law, in order to prov e negligent failure to warn, the plaintiff must show that th e defendant knew or had reason to know about the dangerous condition. Morri s v. Shell Oil Co. , 467 S.W.2d 39, 42 (Mo. 1971) (adoptin g Restatement (Second) of Torts § 388). Air Evac presented evidence that the defendants' engineer: (1) knew that the origina l configuration of the nightscanner tended to remain activated even aft er being switched "off"; (2) did minimal testing of hi s modification to the nightscanner; and (3) did not test the amount of current passing through the relay to ensure that the rela y could accommodate the current. This evidence was sufficient for th e district court to submit the failure to warn instruction to th e jury.

VI De fendants further argue that the district court erred i n denying their motion for a directed verdict and motion for new7

trial because Air Evac failed to establish causation. We re view de
no vo the district court's denial of a motion for judgment as a matter of law, which includes a motion for a directed verdict
. McKnigh t, 36 F.3d at 1400. We apply a much more deferentia l standard in our review of a district court's denial of a mot ion for a new trial: "The [district] court's decision will not be r eversed bya c ourt of appeals in the absence of a clear abuse o f discretion." Lowe v. E.I. DuPont de NeMours & Co. , 802 F.2d 310, 310-11 (8th Cir. 1986).
Defendants allege that Air Eva c's circumstantial evidence did not "tend to exclude any other reasonable conclusion" for th e cause of the accident. See Aetna Cas. and Sur. Co. v. General Ele c. Co. , 758 F.2d 319, 322 (8th Cir. 1985) (under Missouri law, whe n pl aintiff relies on circumstantial evidence in product liabilit y case, evidence must tend to ex clude other reasonable conclusions). Def endants' argument relies on the exclusion of the testimony o f plaintiff's expert Postiglione . As discussed above, Postiglione's testimony was properly admitted. Air Evac, therefore, did n ot rely solely on circumstantial evidence to prove causation. The d istrict court did not err in denying defendants' motion for a directe d verdic t and did not abuse its discretion in denying defendants ' motion for a new trial.

VI
Finally, defendants argue that the district court erroneously awardedpre- and post-judgment interest. We review de nov o questions of state law. Kansas Pub. Employees Retirement Sys. v. Blackwell, Sanders, Matheny, W eary & Lombardi, L.C. , 114 F.3d 679, 687 (8th Cir. 1997).8 A.

Defendants contest the award of pre-judgment interest , calculat edfrom December 4, 1991 to May 5, 1995, on the propert y damage claim. Missouri Rev. Stat. §408.040(2) permits payment of pre-ju dgment interest on tort claims, provided that: 1) th e claima nt demanded payment or offered a settlement, via certifie d mai l, and (2) the judgment obtained exceeds the amount demanded
. Pre -judgment interest is available from 60 days after the deman d was made until the date of judgment.
Defendants argue that Air Evac 's December 4, 1991 letter does not meet these criteria because plaintiff did not send the letter through certified mail and the judgment did not exceed the amount demand ed. In awarding pre-judgment interest, the district cour t
reason edthat because the damages were liquidated, Air Evac wa s entitled to pre-judgment inter est from the date it sent its demand letter.

Because a plain reading of the statute does not support th e district court’s reasoning, we hold that the district court erred in granting pre-judgment interest on the property damage cla im. We remandfor a determination, in accordance with § 408.040, of th e proper pre-judgment interest to be paid, if any, on the propert y damage claim.

B. Defendants also contest the pre-judgment interest award on t he
co ntributionclaim. Again, defendants argue that the distric t
cou rt failed to apply § 408.040 to its determination o f pre- judgment interest and instead improperly relied on case la w ho lding that a liquidated claim is subject to pre-judgmen t interest. The district court, however, correctly concluded that an9

actionfor contribution is not "grounded in tort" but rather i s more like a claim for unjust enrichment. See Rowland v. Skagg s Cos ., 666 S.W.2d 770, 773 (Mo. 1984) (en banc). As such, § 408.040 is i napplicable and pre-judgment interest is available from th e date plaintiffs first demanded payment on the contribution claim. The district court did not err.

C.

Defendants next argue that the district court improperl y applie dthe Missouri pre-judgment statutory interest rate to th e post-judgment interest claim. Defendants correctly state that 28 U.S.C. § 1961 is the applicable statute. Section 1961 provide s that the federal interest rate applies to money judgments in any civil case. Plaintiff concedes this issue. We remand fo r recalculation of post-judgment interest in accordance with 2 8 U.S.C. § 1961.
AFFIRMED in part, REVERSED and REMANDED in part.

A true copy.

Attest: CLERK, U.S. COURT OF APPEALS, EIGHTH CIRCUIT.