Cass Oil Co. [Cass] and World Wide, Inc. [World] appeal from a district court judgment awarding damages to Charles Butz, Jr., for injuries he sustained while riding on a “Super Tube.” We affirm.
On June 16, 1984, Butz was severely injured while riding a “Super Tube” which was sold and distributed by Cass and World. The Super Tube is a large, bright yellow inner tube with handles for the rider. The tube comes with a harness so that it may be attached to a water-ski towrope and pulled behind a boat.
The tube which Butz was riding had been purchased a few weeks earlier by his friend Jack Werner. On the day of the accident Butz and Werner had been fishing. They decided to try out the tube, which Werner had not used before. Butz took the first ride, with Werner driving the boat. Two other people rode along in the boat, with one serving as a spotter.
With Butz on the tube behind the boat, Werner made one or two large circles out in an open area of the river and then headed back near shore. The testimony as to exactly what happened next is somewhat conflicting, but the tube with Butz aboard went skimming along the shoreline for a distance and then slammed into a boat which was sitting partially in the water and partially on the shore. As a result, Butz sustained serious injuries.
Butz sued Werner, World, and Cass, on theories of negligence, strict products liability, and breach of warranty. The case was tried to a jury and the trial court instructed on all three theories. The jury found for Butz on the strict liability theory; found that all four parties were negligent under the negligence theory; and found no breach of warranty.
The verdict form submitted to the jury required separate assessment of fault under the negligence and strict liability theories. On the strict liability theory, the jury assessed fault as follows:
World 37 ½%
Cass 37V2%
Werner 0%
Butz 25%
*511On the negligence theory, fault was assessed as follows:
World 25%
Cass 25%
Werner 15%
Butz 35%
The jury found that Butz’s damages totaled $550,479.79.
The trial court entered judgment on the strict liability claim and dismissed the negligence and breach of warranty claims. The motions of Cass and World for judgment notwithstanding the verdict or a new trial were denied by the trial court. Cass and World have appealed.1
I. DUTY TO WARN
Cass and World assert that the trial court erred in failing to hold that as a matter of law there was no duty to warn.
The parties initially disagree whether the existence of a duty to warn is a question of law for the court or a question of fact for the jury. In a negligence action, whether a duty exists is generally a preliminary question of law for the court. Barsness v. General Diesel & Equipment Co., 383 N.W.2d 840, 843 (N.D.1986). However, if the existence of a duty depends upon factual determinations, their resolution is for the trier of fact. The appropriate procedure in such cases is for the court to instruct the jury as to the defendant’s duty, or absence of duty, if certain facts are found. Barsness v. General Diesel & Equipment Co., supra, 383 N.W.2d at 843; Restatement (Second) of Torts § 328B comment e (1965).
The parties have cast their arguments on this issue in terms of the defendants’ duty to warn. The judgment appealed from, however, is based upon the jury verdict on the strict liability cause of action. The problem with casting the issue in terms of a duty to warn is that it focuses on the defendants’ conduct, whereas strict liability focuses upon the nature of the product. Mauch v. Manufacturers Sales & Service, Inc., 345 N.W.2d 338, 346 (N.D.1984). The relevant inquiry in a strict liability action based upon failure to warn is whether the defendant marketed a product which was unreasonably dangerous to the user because of inadequate warnings. Mauch, supra, 345 N.W.2d at 345.
Whether a product is unreasonably dangerous to the user because of a lack of proper warnings is generally a question of fact. See, e.g., Kysor Industrial Corp. v. Frazier, 642 P.2d 908, 912-913 (Colo.1982) (en banc); Martinez v. Atlas Bolt & Screw Co., 636 P.2d 1287, 1289 (Colo.App.1981); Pepper v. Selig Chemical Industries, 161 Ga.App. 548, 288 S.E.2d 693, 696 (1982); Collins v. Sunnyside Corp., 146 Ill.App.3d 78, 100 Ill.Dec. 90, 92, 496 N.E.2d 1155, 1157 (1986); Ebbert v. Vulcan Iron Works, Inc., 87 Ill.App.3d 74, 42 Ill.Dec. 617, 618, 409 N.E.2d 112, 113 (1980); Phillips v. Kimwood Machine Co., 269 Or. 485, 525 P.2d 1033, 1040 (1974) (en banc); Berg v. Sukup Manufacturing Co., 355 N.W.2d 833, 837 (S.D.1984); Haysom v. Coleman Lantern Co., 89 Wash.2d 474, 573 P.2d 785, 789 (1978); 3 American Law of Products Liability 3d § 32:83, at 126 (1987).
We noted in Mauch, supra, that “ ‘[i]t is the adequacy of the warning which is given, or the necessity of such a warning, which must command the jury’s attention, not the defendant’s conduct.’ ” Mauch, supra, 345 N.W.2d at 346 (quoting Little v. PPG Industries, Inc., 92 Wash.2d 118, 594 P.2d 911, 914 (1979) (en banc)). In Stillwell v. Cincinnati Inc., 336 N.W.2d 618, 622 (N.D.1983), a strict liability action based on both design defect and failure to warn, we stated that “whether or not a manufacturer fits within the parameters of strict liability in tort is essentially a factual question for the trier of fact.”
Cass and World assert that there was no duty to warn in this case because the dangers of using the Super Tube were open and obvious. In the context of a strict liability action, their argument must be that the lack of warnings did not render the Super Tube unreasonably dangerous because, as a matter of law, the dangers *512were open and obvious. Assuming for the purpose of argument that openness and obviousness of the dangers may constitute an absolute defense in a strict liability action based upon failure to warn,2 we find no merit in the defendants’ contentions under the facts of this case. Cass and World argue that it is apparent to everyone of common intelligence that there is danger in colliding with a fixed object. Butz, however, has never asserted that Cass and World should have warned that it was dangerous to crash the Super Tube into a fixed object. Butz’s contention, which was supported by expert testimony, was that Cass and World should have warned that the Super Tube should not be towed above a certain speed; that the Super Tube would accelerate and arc around comers; that the rider would have no control of the direction or speed of the Super Tube; and that the rider’s visibility would be impaired by the “spray” from the Super Tube. It was this failure to warn of speed restrictions, excessive arcing, lack of control, and lack of visibility which Butz asserts was a primary cause of the collision.
We conclude that the trial court did not err in failing to rule as a matter of law that the open and obvious nature of the dangers associated with the Super Tube obviated any need for warnings. The court properly submitted to the jury the issue whether the Super Tube was unreasonably dangerous because of the lack of warnings.
II. CAUSATION
Cass and World assert that Butz failed to prove that the lack of warnings on the Super Tube was a direct cause of his injuries.
Proximate causation in a negligence case is a question of fact. E.g., Priel v. R.E.D., Inc., 392 N.W.2d 65, 69 (N.D.1986). Implicit in our holding in Mauch, supra, is that proximate causation is also a question of fact in a strict liability case. See Mauch, supra, 345 N.W.2d at 347-348. Courts in other jurisdictions have expressly so held. E.g., Prince v. Parachutes, Inc., 685 P.2d 83, 89 (Alaska 1984); Kavanaugh v. Kavanaugh, 131 Ariz. 344, 641 P.2d 258, 266 (Ct.App.1981).
Our review of questions of fact in a jury case is limited to consideration of whether there is substantial evidence to sustain the verdict. Farmers Co-op. Elevator of Cavalier v. Lemier, 328 N.W.2d 833, 835 (N.D.1982). We will not invade the province of the jury to weigh evidence or determine the credibility of witnesses. Farmers Co-op. Elevator, supra. We view the evidence in the light most favorable to the verdict and if there is substantial evidence to support the verdict we will not set it aside. Farmers Co-op. Elevator, supra.
Cass and World assert that the lack of warnings did not proximately cause the accident; Butz and Werner assert that it did. There is evidence in the record to support a finding either way. Under these circumstances, we will not substitute our judgment for that of the jury, which heard the testimony and had the opportunity to judge the credibility of the witnesses. See Hoerr v. Northfield Foundry and Machine Co., 376 N.W.2d 323, 326 (N.D.1985). We conclude that there is substantial evidence to support the jury's finding that the lack of warnings proximately caused Butz’s injuries.
*513EXPERT TESTI-III. ADMISSION OF MONY
Cass and World assert that the trial court erred in allowing Butz’s expert witness, Albert Tillman, to testify regarding the necessity of specific warnings on the Super Tube.
Admission of expert testimony is governed by Rule 702, N.D.R.Evid.:
“If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”
The test for admission of expert testimony under Rule 702 is whether such testimony will assist the trier of fact and whether the witness is qualified as an expert. Patch v. Sebelius, 349 N.W.2d 637, 643 (N.D.1984). The determination to admit expert testimony rests within the sound discretion of the trial court, and its determination will not be disturbed on appeal unless the court has abused its discretion. Victory Park Apartments, Inc. v. Axelson, 367 N.W.2d 155, 163 (N.D.1985). .
It was for the trial court to determine whether Tillman was qualified to testify as an expert and whether his testimony would assist the jury. We have reviewed the record and we conclude that the trial court did not abuse its discretion in allowing Tillman to testify.
IV. ELECTION OF THEORY OF RECOVERY, PERVERSITY OF VERDICT, AND COMBINED FAULT ASSESSMENT
Cass and World next assert three intertwined arguments. They assert that: (1) the trial court should have required Butz to elect one theory of recovery before submission to the jury, rather than submitting negligence, strict liability, and breach of warranty; (2) the jury verdict, which assessed different percentages of fault to each party under the separate negligence and strict liability theories, was illogical, perverse, and irreconcilable; and (3) if multiple theories were submitted, the trial court should have submitted them to the jury on a combined fault assessment form, rather than with separate fault assessments for the differing theories.
A. Election of Theories
Cass and World assert that it was error to allow the case to go to the jury on multiple theories, and that the trial court should have required Butz to elect one theory of recovery.
Rules 8(a) and 18(a), N.D.R.Civ.P., generally allow a party to plead multiple claims against another party. In the specific context of a failure-to-warn case premised on both negligence and strict liability, we have held:
“Although the authorities disagree over this issue, we believe that recovery sought under a negligent failure-to-warn theory and recovery sought under a products-liability theory of marketing a product which is defective and unreasonably dangerous because it is not accompanied by adequate warnings are two separate and distinct theories of recovery. Thus the trial court must instruct on each where there is evidence to support both theories.” Mauch, supra, 345 N.W.2d at 345.
The trial court did not err in refusing to require Butz to elect one theory of recovery.
B. Perversity of the Verdict
Cass and World assert that the verdict is illogical, perverse, and irreconcilable because the jury assessed different percentages of fault under the negligence theory and the strict liability theory.
The jury assessed fault as follows:
[[Image here]]
World WIWo
Cass 37⅛ %
Werner 0%
Butz 25%
100%
NEGLIGENCE
World 25%
Cass 25%
Werner 15%
Butz 85%
100%
Cass and World assert that fault is fault, and the percentages should not vary under the differing theories. Cass and World, *514however, are analyzing the issue from a purely factual perspective. There may be a distinction between factual “fault” and legal “fault,” depending upon the legal theory imposed.
In Mauch, supra, we held that ordinary contributory negligence is not a defense in a strict liability action:
“We believe the better rationale, and the one we choose to follow in this case, is that the plaintiff’s conduct should not be scrutinized in ordinary ‘contributory negligence’ terminology as a defense to a products-liability claim. The focus of a products-liability action is on whether or not the product is defective and unreasonably dangerous, and thus the reasonableness of the defendant’s conduct under negligence concepts is not relevant to this action. The defenses which we have previously recognized in [Olson v. A.W. Chesterton Co., 256 N.W.2d 530 (N.D.1977) ] of assumption of risk and unforeseeable misuse are, in our opinion, adequate to protect a seller or manufacturer from unjust liability in a case of this type.” Mauch, supra, 345 N.W.2d at 347.
We explained the rationale of our holding:
“The defenses of assumption of the risk and product misuse focus, as does the products-liability claim itself, upon the nature of the product and its use. We believe that the interjection of ordinary contributory negligence principles would only serve as a diversion from the proper focus on the product and its use in such a case without providing any needed additional protection to the defendant seller or manufacturer which the defenses of assumption of risk and unforeseeable misuse of the product do not already provide.” Mauch, supra, 345 N.W.2d at 347.
Thus, ordinary negligence of the plaintiff or a third party3 which does not constitute assumption of risk or unforeseeable misuse is irrelevant in a strict liability action, and cannot be compared with the manufacturer or seller’s strict liability in assessing fault.
In light of Mauch, it is easily understandable how the jury in this case assessed different percentages of fault under the different legal theories. The ordinary negligence of Butz and Werner is considered for purposes of assessing fault under the negligence theory, but is wholly irrelevant in the strict liability action. This ordinary negligence, although clearly a factual “fault” of the accident, is not a legal “fault” under the strict liability theory.
Thus, in the negligence action, the jury considered Butz and Werner’s ordinary negligence and assessed Butz thirty-five percent fault and Werner fifteen percent fault. Under the strict liability theory Butz and Werner’s conduct was relevant only to the extent it constituted assumption of risk or unforeseeable misuse. The jury assessed Butz twenty-five percent fault, apparently concluding that Butz’s conduct constituted assumption of the risk. The jury assessed Werner no fault under the strict liability theory, apparently concluding that Werner’s conduct did not rise to the level of unforeseeable misuse.
We conclude that the verdict is not “illogical, perverse, and irreconcilable.” Instead, the verdict demonstrates that the jury carefully followed the trial court's instructions, which clearly and explicitly spelled out the differing considerations and defenses available under the negligence and strict liability theories.
C. Combined Fault Assessment Form
Cass and World assert that the trial court erred in refusing their request *515that the case be submitted on a combined fault assessment form.
We expressly reserved resolution of this question in Hoerr v. Northfield Foundry and Machine Co., 376 N.W.2d 323, 327 (N.D.1985), because the defendant had failed to preserve the issue in the trial court. Our resolution of the issue, however, follows by implication from our analysis in Mauch. As previously discussed, ordinary negligence is not a defense in a strict liability action, and the ordinary negligence of the plaintiff or a third party is not to be considered in assessing fault. Thus, the ordinary negligence of the plaintiff or a third party cannot be employed to diminish the percentage of fault attributable to the defective nature of the product.
Cass and World have not offered a plausible verdict form which would combine fault assessment for the negligence and strict liability theories, yet isolate the determination of strict liability percentages from the ordinary contributory negligence considerations applicable to the negligence cause of action. Nor can we envision a verdict form which would combine fault assessment of the two theories without eviscerating Mauch. Using any combined assessment form, an increase or decrease in the percentage of negligence attributed tó Butz or Werner would have a corresponding effect on the percentage of fault left available to assess against Cass and World on the strict liability claim. Mauch clearly prohibits such a result.
Strict products liability and negligence are “separate and distinct theories of recovery.” Mauch, supra, 345 N.W.2d at 345. Strict liability focuses upon the product and its use, whereas negligence focuses on the conduct of the parties. Different defenses are available under the two theories. Our analysis leads to the conclusion that there is no logical method to combine fault assessment under the two theories without effectively blending them to the point of destroying their functions as separate theories of recovery.
Our conclusion today is bolstered by our holding in Hoerr, supra, where the appropriateness of using separate fault assessment forms was questioned on appeal, but the defendant had failed to object to the special verdict form in the trial court. We were, however, required to determine the effect of the combined fault assessment form. The defendant argued that the fairest compromise would be to average the strict liability and negligence fault assessments, rather than allow Hoerr to choose to have judgment entered on the theory which provided the greater amount of recovery. We rejected the defendant’s contention, and expressly agreed with the following rationale of the Supreme Court of New Jersey in a similar case:
“ ‘We perceive of no reason to disavow th[e strict liability] verdict merely because the plaintiff was also found entitled to recover due to Fireco’s negligence. Where a defendant is found liable on the theory of strict liability, plaintiffs entitlement to recovery should not be diminished or altered because defendant is also liable on another theory of wrongdoing.... “When a jury verdict sustains several alternative theories of recovery advanced by a plaintiff, the trial court must [unless plaintiff chooses otherwise] render judgment on the theory which affords the greatest recovery.” Mowery v. Fantastic Homes, Inc., 568 S.W.2d 171, 173 (Tex.Civ.App.1978).’” Hoerr, supra, 376 N.W.2d at 328 (quoting Cartel Capital Corp. v. Fireco of New Jersey, 81 N.J. 548, 564-565, 410 A.2d 674, 682-683 (1980)).
This rationale supports our conclusion that separate fault assessment forms are proper. We believe that if a combined fault assessment form were used, in many cases a plaintiff’s recovery would be “diminished or altered because defendant is also liable on another theory of wrongdoing.” A combined fault assessment form would effectively require comparison of the defendant’s strict liability with the plaintiff’s ordinary negligence, which is a factual fault of the accident but is not legal fault under a strict products liability claim. The result could be to improperly diminish or alter the recovery which the plaintiff would have been entitled to under separate *516fault assessments. We can discern no reason why a plaintiff who can prove two separate causes of action, and thus two separate wrongs by the defendant, should be required to risk diminution of his recovery because he prevails on both theories. If the plaintiff can prove two separate theories he is entitled to have the jury instructed on the separate theories, to have fault assessed separately on each theory, and to have judgment entered on the theory which provides the greater recovery. See Hoerr, supra, 376 N.W.2d at 327-328.
Cass and World suggest that a recently enacted statute, Chapter 32-03.2, N.D.C.C., requires that combined fault assessment forms be used in cases such as this. Initially we note that Chapter 32-03.2 applies only to claims accruing after July 8, 1987. Cass and World assert that they do not seek retroactive application of the statute, but rather suggest that the statute is indicative of the state’s public policy and should be used to “fill the void” left from our prior decisions.
Cass and World rely upon Davis v. Auto-Owners Insurance Co., 420 N.W.2d 347 (N.D.1988), to support their argument. In Davis we noted that a later-enacted statute may be indicative of earlier public policy “[ajbsent anything contrary.” Davis, supra, 420 N.W.2d at 349. As previously discussed, however, Mauch is contrary to Cass and World’s interpretation of the public policy expressed in the statute, and adoption of their argument would not merely “fill the void” but would seriously erode the holding of Mauch. We will not apply the statute retroactively, and we will not adopt the alleged public policy basis of the statute in resolving this case.4
We conclude that the trial court did not err in refusing to submit a combined fault assessment form.
V. FAULT ASSESSMENT
Cass and World assert that Werner’s fault exceeded Butz’s fault as a matter of law, and that the jury’s fault assessment under the strict liability and negligence theories demonstrates that the verdict was perverse and unsupported by the evidence.
Issues of negligence, proximate cause, and comparative negligence are questions of fact for the trier of fact unless the evidence is such that reasonable minds can draw but one conclusion. Layman v. Braunschweigische Maschinenbauanstalt, Inc., 343 N.W.2d 334, 339 (N.D.1983); Bauer v. Graner, 266 N.W.2d 88, 92 (N.D.1978). Apportionment of fault is also a question of fact. See Bauer, supra, 266 N.W.2d at 92. Our review is thus limited to consideration of whether there is substantial evidence to sustain the verdict, and we will view the evidence in the light most favorable to the verdict. Farmers Co-op. Elevator of Cavalier v. Lemier, 328 N.W.2d 833, 835 (N.D.1982).
There was much conflicting evidence regarding the cause of the accident in this case, and of Butz and Werner’s conduct. We will not invade the province of the jury to weigh evidence or determine the credibility of witnesses. Farmers Co-op. Elevator, supra, 328 N.W.2d at 835. We conclude that there is substantial evidence to support the jury’s assessment of percentages of fault.5
VI. PRESUMPTION THAT WARNING WOULD BE HEEDED
Cass and World assert that the trial court erred in instructing the jury that it is presumed that had adequate warnings been given they would have been read and heeded. Cass and World argue that no such presumption is recognized under North Dakota law and that, even if it were, *517it was error to instruct the jury on the presumption.
Our strict products liability caselaw has relied heavily upon Section 402A, Restatement (Second) of Torts (1965). Comment j to Section 402A provides, in pertinent part:
“Where warning is given, the seller may reasonably assume that it will be read and heeded; and a product bearing such a warning, which is safe for use if it is followed, is not in defective condition, nor is it unreasonably dangerous.”
Numerous courts have relied upon Comment j in adopting a corollary presumption: that where no warning is given it may be presumed that, had an adequate warning been given, it would have been read and heeded. See, e.g., Reyes v. Wyeth Laboratories, 498 F.2d 1264, 1281 (5th Cir.) (applying Texas law), cert. denied, 419 U.S. 1096, 95 S.Ct. 687, 42 L.Ed.2d 688 (1974); Nissen Trampoline Co. v. Terre Haute First National Bank, 332 N.E.2d 820, 826-827 (Ind.Ct.App.1975), rev’d on procedural grounds, 265 Ind. 457, 358 N.E.2d 974 (1976); Wooderson v. Ortho Pharmaceutical Corp., 235 Kan. 387, 681 P.2d 1038, 1057, cert. denied, 469 U.S. 965, 105 S.Ct. 365, 83 L.Ed.2d 301 (1984); Wolfe v. Ford Motor Co., 6 Mass.App.Ct. 346, 376 N.E.2d 143, 147 (1978); Seley v. G.D. Searle & Co., 67 Ohio St.2d 192, 423 N.E.2d 831, 838 (1981); Technical Chemical Co. v. Jacobs, 480 S.W.2d 602, 606 (Tex.1972). But see Potthoff v. Alms, 41 Colo.App. 51, 583 P.2d 309, 311 (1978). Other courts have employed the same presumption without specifically relying upon Comment j. See, e.g., Payne v. Soft Sheen Products, Inc., 486 A.2d 712, 725 (D.C.1985); Benoit v. Ryan Chevrolet, 428 So.2d 489, 493 n. 8 (La.Ct.App.1982); Cunningham v. Charles Pfizer & Co., 532 P.2d 1377, 1382 (Okla.1974); Menard v. Newhall, 135 Vt. 53, 373 A.2d 505, 506 (1977). See also 3 American Law of Products Liability 3d § 32:74, at 118 (1987).
The rationale behind this approach is that it is a logical interpretation of Comment j. If the seller is entitled to a presumption that an adequate warning will be read and heeded, the plaintiff should be entitled to the converse presumption when no warning, or an inadequate warning, is given. As noted by several courts, the presumption works in favor of the manufacturer or seller when an adequate warning is present, but in favor of the plaintiff user when no warning is given. See, e.g., Reyes v. Wyeth Laboratories, supra, 498 F.2d at 1281; Nissen Trampoline Co. v. Terre Haute First National Bank, supra, 332 N.E.2d at 826; Seley v. G.D. Searle & Co., supra, 423 N.E.2d at 838; Technical Chemical Co. v. Jacobs, supra, 480 S.W.2d at 606.
We also agree with the reasoning of the Appeals Court of Massachusetts in Wolfe v. Ford Motor Co., supra, 376 N.E.2d at 147:
“An adequate warning is by definition one that would in the ordinary course have come to the user’s attention. The failure to give such a warning therefore permits the inference that it would have alerted the user to the danger and forestalled the accident.”
We conclude that when no warning is given the plaintiff is entitled to the benefit of a presumption that an adequate warning, if given, would have been read and heeded.
Cass and World also assert that, even if such a presumption is applicable, the jury should not have been instructed on the presumption. Cass and World assert that the jury should simply have been instructed that Cass and World had the burden of proving that Butz would not have read nor heeded an adequate warning.
Under Rule 301(a), N.D.R.Evid., a presumption “substitutes for evidence of the existence of the fact presumed until the trier of fact finds from credible evidence that the fact presumed does not exist,” and the “party against whom a presumption is directed has the burden of proving that the nonexistence of the presumed fact is more probable than its existence.” Thus, Rule 301(a) shifts the burden of proof. Victory Park Apartments, Inc. v. Axelson, 367 N.W.2d 155, 161 n. 4 (N.D.1985).
The trial court instructed the jury that there was a presumption that if adequate *518warnings had been given Butz would have read and followed them. The court further instructed the jury regarding the effect of the presumption, and that Cass and World had the burden of proving that the nonexistence of the presumed fact was more probable than its existence.
Although the instruction suggested on appeal by Cass and World may have been a correct statement of the law, the trial court need not give instructions in the specific language requested by a litigant. Instructions which fairly inform the jury of the applicable law are all that is required. Andrews v. O'Hearn, 387 N.W.2d 716, 727 (N.D.1986); Matter of Estate of Knudsen, 342 N.W.2d 387, 392 (N.D.1984).
We conclude that the instruction, as a whole, fairly and adequately apprised the jury of the law, and we therefore find no reversible error in the instruction given by the trial court.
VII.EXCLUSION OF VIDEOTAPE AND PHOTOGRAPHS
Cass and World assert that the trial court erred in refusing to admit into evidence a videotape and photographs of a reconstruction of the accident performed by a private investigator hired by Cass and World. Cass and World assert that the videotape and photographs would have shown the amount of “spray” from the Super Tube and its handling and arcing when towed behind a boat.
The determination whether to admit demonstrative evidence, including experiments, demonstrations, and tests, is left to the sound discretion of the trial court and will not be disturbed on appeal unless an abuse of discretion is shown. Van Ornum v. Otter Tail Power Co., 210 N.W.2d 188, 196-197 (N.D.1973). A trial court abuses its discretion when it acts in an unreasonable, arbitrary, or unconscionable manner. E.g., Eisenzimmer v. City of Balfour, 352 N.W.2d 628, 631 (N.D.1984).
We have reviewed the videotape and photographs in the context of this record and we conclude that the trial court did not abuse its discretion in excluding this evidence.
VIII. JURY INSTRUCTIONS
Cass and World assert that the trial court erred in refusing to give several other requested jury instructions. We have reviewed these proposed jury instructions and we conclude that it was not reversible error to refuse the proposed jury instructions.
IX. CROSS APPEAL
As previously noted, Butz has filed a cross-appeal seeking a new trial on Wer-ner's liability if a new trial is granted to Cass and World. Butz has conceded that its cross-appeal should be denied if Cass and World’s appeal fails. Because we affirm the judgment based upon strict products liability against Cass and World it is unnecessary to reach the cross-appeal.
The judgment of the district court is affirmed.
ERICKSTAD, C.J., and VANDE WALLE, J., concur.. Butz has filed a cross-appeal alleging that, if a new trial is necessary, the issue of Werner's liability under the negligence theory should be included in the retrial.
. The appellees have not challenged Cass and World's assertion that openness and obviousness of the danger wholly obviates the necessity of a warning. We have previously noted, however, that obviousness of the danger does not automatically preclude liability in a strict liability failure-to-warn case. Olson v. A.W. Chesterton Co., 256 N.W.2d 530, 537 (N.D.1977). We agreed with cases from other jurisdictions holding that obviousness of the danger is merely one factor to be considered in determining whether the product is unreasonably dangerous. Olson, supra, 256 N.W.2d at 537.
Cass and World assert that we held that there was no duty to warn of open and obvious dangers in Stillwell v. Cincinnati Inc., 336 N.W.2d 618 (N.D.1983). The language quoted by Cass and World to support their contention, however, is language we quoted from the trial court's memorandum opinion in that case. We specifically declined to consider the open and obvious danger doctrine, instead relying upon the trial court's findings that there were adequate warnings given and that the product was therefore not unreasonably dangerous. Stillwell, supra, 336 N.W.2d at 624.
. Cass and World assert that Mauch addresses only the plaintiff’s negligence, and suggest that Mauch would not preclude a defense based upon a third party’s ordinary negligence. Cass and World cite no authority for this assertion. Furthermore, we see no logical reason to differentiate between the plaintiff’s ordinary negligence and that of a third party for strict liability purposes. The same rationale would apply: “the interjection of ordinary contributory negligence principles would only serve as a diversion from the proper focus on the product and its use.” Mauch, supra, 345 N.W.2d at 347. If the third party’s conduct constituted unforeseeable misuse of the product it could serve as a defense pursuant to Mauch.
. We express no opinion whether, as Cass and World assert, Chapter 32-03.2, N.D.C.C., requires the use of a combined fault assessment form in a case involving both negligence and strict liability claims which accrues after July 8, 1987.
. Cass and World also assert that the jury's assessment of no fault to Werner on the strict liability theory is unsupported by the evidence. As previously discussed, however, the jury’s assessment is easily explained by the fact that Werner’s ordinary negligence is not a defense and cannot be considered in assessing fault under the strict liability claim.