MR. JUSTICE MORRISON
delivered the opinion of the Court.
This is an appeal by defendant from judgment entered May 15, 1981, by the Third Judicial District Court following a jury verdict in favor of plaintiff for $1,390,000.00 and from the order entered thereafter on post-trial motions. Plaintiff cross-appeals.
Plaintiff’s legs were traumatically amputated by an explosion on February 6, 1977. Plaintiff, employed at the Anaconda Smelter in Anaconda, Montana, had been engaged in a conversation with a co-employee, Larry Raver. During the conversation, Raver picked up a “projectile” or large shell from his nearby truck and was holding it in his hands. Raver explained to the plaintiff that the shell was a dud but that it was designed to “go off” in a certain manner. When Raver was concluding this statement, the plaintiff concerned of the danger, began running for safety. The shell exploded. Raver was killed and plaintiff’s injuries ensued.
Plaintiff filed suit against the Montana National Guard and the State of Montana alleging that the decedent Raver obtained the shell from the National Guard firing range in the Deer Lodge-Mt. Powell area. Plaintiff’s proof established that the National Guard held exercises in this area and that large ammunition was left after the exercises. Plaintiff alleged negligence in failure to clean up the area and in leaving live ammunition where the public had access to it. Substantial credible evidence established a case of negligence and defendants do not appeal that determination. Defendants contend that plaintiff totally failed to prove that Raver obtained the shell in question from the firing range near Deer Lodge.
Two other issues are presented for review. Defendants contend that the present limitation on state liability for damages should apply or, in the alternative, that any recov[496]*496ery should be limited to applicable insurance limits. In a cross-appeal plaintiff challenges the constitutionality of section 2-9-317, MCA, which exempts the State from paying interest on judgments for a two year period. The sufficiency of evidence question must be decided first.
SUFFICIENCY OF EVIDENCE
Plaintiff’s case for proximate cause was supported by the following:
(1) Plaintiff’s testimony that the shell which caused his injuries was approximately eighteen inches long and about three inches in diameter;
(2) Evidence from the National Guard that exercises near Deer Lodge had included the firing of a projectile about eighteen inches long with a three-four inch diameter;
(3) Testimony from several witnesses that large live rounds had been found in the area of Mt. Powell;
(4) Deposition testimony from Larry Raver’s widow establishing that Raver had traveled by motorcycle in the Mt. Powell area and during his motorcycle travels had collected what might be termed “junk items”;
(5) Larry Raver, while demonstrating a large shell to a co-employee prior to this accident, stated that he had found the shell;
(6) Other sources of the shell in question were few, if any.
Defendant countered with expert testimony tending to prove that the round which exploded and injured the plaintiff was a 2.75 inch rocket round with a mark-176 fuse. Defendants’ evidence further sought to prove that such a rocket round had never been fired by the Montana National Guard at the Deer Lodge firing range.
The issue is whether plaintiff’s circumstantial evidence was sufficient to create a jury issue on proximate cause. It is incumbent upon the plaintiff to present evidence from which a jury might reasonably infer that Larry Raver obtained the shell in question from the National Guard firing range near Deer Lodge. Circumstantial evidence sufficient to prove proximate cause in a civil cause need not exclude [497]*497every reasonable conclusion other than the conclusion sought to be established. Lenherr v. NRM Corp. (D.Kan.1980), 504 F.Supp. 165. Plaintiff’s evidence is sufficient if it affords a basis for a reasonable inference by the trier of fact although there are other reasonable inferences which might be drawn by that trier of fact. Arterburn v. St. Joseph Hospital and Rehabilitation Center (1976), 220 Kan. 57, 61, 551 P.2d 886, 891.
With these rules in mind, we will not review that evidence offered by the plaintiff to prove the proximate cause thesis. Upon this evidence, the plaintiff’s contention for a submis-sible jury issue must rise or fall.
The following testimony was given by Gerald Effing, retired National Guard Colonel:
“Q. Did you know anything about the firing area down in Deer Lodge?
“A. Yes, I did.
“Q. Could you tell us what you knew about that area?
“A. Well, we started firing there in 1956 and fired there in ‘56 and ‘57 and then we went down to Townsend in 1958 or about 1961 and then went back to Deer Lodge for ‘62 through ‘66.
“Q. What type of guns or what did you fire there?
“A. Well, the artillery, we had 105 millimeter howitzers and we had 155 millimeter howitzers.
“Q. And the ammunition which the artillery fired, was that all live ammunition?
“A. Yes, it was.
“Q. First, could you state what the general size of a 105 projectile is?
“A. As far as length?
“Q. Just generally.
“A. It would probably be 18 inches long.
“Q. Okay.
“A. About three or four inches in diameter.”
[498]*498The following testimony of the plaintiff was offered to show the similarity of the shell which injured the plaintiff. Mickey Jacques testified:
“Q. Did you have a chance to look at the shell he was holding?
“A. Yes.
“Q. And could you describe it for us?
“A. Yes. It was a foot — approximately a foot and a half long and about three inches in diameter.”
Plaintiff sought through several witnesses to establish the existence of similar rounds following National Guard exercises. The following testimony is illustrative. Charles Fudge, Forester, U.S. Forest Service, testified:
“Q. Prior to this first time you came in contact in June of 1969 with the National Guard people had you ever been on the Montana State Prison property or forest service property in the vicinity where this fire occurred?
“A. Yes,
“Q. Had you ever observed any rounds or projectiles out there?
“A. Yes. To the best of my recollection, it would have been in the fall. It would have been in the fall of 1968.
“Q. Do you recall where you were when you observed these projectiles?
“A. They were on the face of a grassland area leading up towards Deer Lodge Mountain and Mount Powell ridge, both on Montana State Prison land and at the top of the edge of a grass opening where timber began. I observed one or more projectiles on National Forest lands.”
“Q. Have any other other incidents come to your attention where high explosive projectiles have been found in the area?
“A. Yes.
“Q. When was that?
“A. I believe that was in 1972.
“Q. Would you relate what your recollection of those events were?
[499]*499“A. Yes. Rob Malinsky, who was an assistant of mine at Deer Lodge, came to me one day and indicated that he had a report from a Deer Lodge resident, as I recall, who had found some projectiles along the shore or just within Powell Lake.”
Laurence Lambert, Montana State Prison employee, testified:
“Q. What area did you see those shells in? Is there a creek or something?
“A. It’s on the ridge between Tin Cup Creek and Robinson Creek. There’s a horse trail that goes to the lake and it’s right where the horse trail breaks at the top of the ridge.
“Q. How long ago did you see these shells?
“A. I would say it was ‘77 or ‘78.
“Q. Has there been more than one shell you’ve observed out there?
“A. Yes.
“Q. How many would you say?
“A. Oh, about 30.”
Other corroborative evidence was received but the testimony quoted above represents the type of proof offered by the plaintiff to establish the existence of large shells in the area of the Deer Lodge firing range.
Plaintiff produced through deposition testimony of Larry Raver’s widow, evidence that Raver traveled in the area where similar rounds were known to have existed. In pertinent part, she testified as follows:
“Q. Would he ride his bike twelve months out of the year?
“A. Yes.
“Q. Do you have any idea where he rode, Delores?
“A. Well, I know for a fact that he rode on the mountains up above our house. He rode quite a bit around Helena, he rode a lot over towards Wisdom and German Gulch. He just crisscrossed everywhere on that bike.
“Q. Did Larry ever bring anything back with him, Delores, when he was on these rides?
[500]*500“A. He would bring back little things that he found of interest. He might spend an afternoon going through an old rambled-down shack and anything that be thought was adventurous, he would bring it home.
“Q. How would he carry these things?
“A. I had bought him a set of saddlebags for the bike and they got torn, so he put a rack on the back of the bike and he had a box fixed to it that he could put his things in.
“Q. Where did Larry used to fish, Delores?
“A. Mainly in rivers and streams, but all over the State — or this part of the State.
“Q. Do you know whether he ever camped or fished in any of the mountain lakes up in the Racetrack or Mount Powell area?
“A. Yes, he went up there frequently.”
Plaintiff offered the testimony of co-employees, that Raver had displayed a large projectile to them at a time prior to this accident, and had told them where he had found it. Defendants objected on the basis of hearsay and the objection was sustained. However, the following testimony was introduced through James Ficklin, a co-employee, and was received without objection:
“Q. Did you ever see a shell in Larry Raver’s possession up on the hill?
“A. . . . I’m not sure of the exact date. It seems to me it was a couple weeks prior to when Mick was injured and Larry was killed ... I was late for work that day and Larry followed me into the lot . . . he did specify that he had something that he wanted to show me that he found.
“Q. When he pulled up behind you and stopped you, did he get out of the car?
“A. I pulled in and parked my vehicle and when I got out, Larry was outside of his truck but he had his door open. What he was doing was security. When I turned, I walked up and approached the vehicle and when I turned around, I could see some sort of projectile.”
Testimony that Raver found a shell, which may have been [501]*501the one responsible for plaintiff’s injuries, provides evidence from which the jury could rule out several alternative sources, i.e., that Raver brought the shell home from Vietnam or that he purchased it from anyone.
Plaintiff offered other testimony tending to prove that the plaintiff had not traveled widely outside of Montana, had not brought the shell back from Vietnam, and generally proved the lack of other sources for a projectile similar to the one which injured the plaintiff.
Defendant produced expert testimony, which, if believed, established that the round which injured the plaintiff had not been fired at the Deer Lodge firing range. It is unnecessary to detail this testimony. Plaintiff was able to impeach the credibility of defense experts to some extent, but the expert testimony remained sufficiently strong to support a defense verdict had one been rendered.
In Tompkins v. Northwestern Union Trust Co. of Helena, Montana (1982), Mont., 645 P.2d 402, 408, 39 St.Rep. 845, 853, we stated that: “The jury can choose to adopt the testimony offered by one side to the exclusion of the other. The jury is free to disregard all of the expert testimony.” In most cases, expert testimony does not mandate a result because, by its nature, expert testimony deals with opinion evidence. Irrefutable facts need not be established, and most likely would not be established, through offering expert opinion. Nevertheless, we have sought guidance from other jurisdictions. The cases which bear most directly upon the issue to be here resolved are cases dealing with product identification. In those cases the plaintiff was injured by a defective product and the defendant contended plaintiff had failed to prove that defendant was related to the product in question.
In Smith v. J. C. Penney Company, Inc. (1974), 269 Or. 643, 525 P.2d 1299, plaintiff was badly burned when a gasoline fire ignited her coat. Suit was instituted against the retailer, J. C. Penney Company, and against Bunker-Ramo, alleged by plaintiff to have supplied the fabric used by the [502]*502manufacturer. A verdict was returned against Bunker-Ramo who then appealed. Plaintiff sought to prove that a Borg trade name on the fabric identified defendant Bunker-Ramo as the supplier. At trial, Rothman, an employee of the manufacturer Roseta, explained that the identification linking Bunker-Ramo to the fabric was meaningless; that from June 2, 1970, forward, Roseta obtained fabric from both Mauldin Mills and Bunker-Ramo but that all fabrics, including those obtained from Mauldin Mills bore the Bunker-Ramo label. Therefore, it was concluded that it would be impossible to tell whether the fabric in question came from Bunker-Ramo or from Mauldin Mills. Bunker-Ramo further offered expert testimony from an employee who testified that an analysis of plaintiff’s coat showed that the fabric in plaintiff’s coat definitely was supplied by Mauldin Mills and not Bunker-Ramo. This evidence was not contradicted by other expert testimony. On appeal the question was whether there was sufficient evidence linking the coat to defendant, Bunker-Ramo. In sustaining the jury verdict, the Supreme Court of Oregon said:
“Or the jury could find that even if it were manufactured subsequent to June 2, 1970, the notations on the cutting order and the tags proved Roseta used Borg fabrics. They could disbelieve Rothman’s explanation that such notations did not prove Borg fabrics were used.” 525 P.2d at 1302.
In commenting on defendant’s expert testimony, the Oregon court said:
“The jury did not have to accept the testimony of Mr. Swihart although his testimony was not directly contradicted.” 525 P.2d at 1303.
The Oregon court held that the witness was sufficiently impeached for credibility to be a jury issue.
In Neubauer v. Coca Cola Bottling Company of Chicago. (1968), 96 Ill.App.2d 18, 238 N.E.2d 437, plaintiff was injured by the putrid contents of a Coca Cola. Plaintiff offered proof that the Coca Cola bottle was a ten-ounce bottle purchased from “Tony’s Liquor Store.” The owner of [503]*503Tony’s Liquor Store testified that defendant had never supplied him ten-ounce Coke bottles. The Illinois court held that such testimony did not foreclose a verdict for plaintiff. The court said:
“The defendant relies, primarily, on the fact that the Coke in question was in a ten-ounce bottle; that the store owner and the defendant’s employees testified that ten-ounce bottles of Coke were not sold to the store; that the defendant’s witnesses stated that ten-ounce bottles are sold to business entities where there is on-the-premises consumption through coin operated coolers, and to certain other outlets for resale in case lots as leader items . . .
“We cannot say that the plaintiff’s testimony, and the further evidence that the defendant was the exclusive distributor in the area, and that Tony’s Liquor Store purchased its Coke from the defendant, is of insufficient probative value to show that the Coke in question was bottled by the defendant. The direct, positive evidence relative to the ten-ounce bottle was conflicting. From this evidence the jury might well have determined that a ten-ounce bottle was mistakenly delivered to Tony’s Liquor Store by the defendant. Whatever else it may have determined on the basis of these facts, there was adequate evidence for a jury to decide that the Coke in question was bottled and sold by the defendant.” 238 N.E.2d at 439-440.
We think expert testimony offered by defendant, though unrefuted except for impeachment, does not compel or mandate a result for defendant. The jury should be free to weigh that testimony and should be able to accept or reject it.
We must here decide whether, viewing the evidence in a light most favorable to plaintiff, a jury issue was created. Plaintiff offered no direct evidence to prove that decedent Larry Raver obtained the projectile which injured the plaintiff, from the firing range near Deer Lodge. Whether plaintiff has succeeded in creating a submissible fact question to proximate cause presents a close question to this [504]*504Court. The resolution of this question necessarily involves evaluating the role of a trial judge or appellate court in removing cases from jury consideration.
The following language from Karczewski v. Ford Motor Company (N.D.Ind.1974), 382 F.Supp. 1346, aff’d 515 F.2d 511 (7th Cir.1975), is instructive.
“Motions for directed verdict or for judgment N.O.V. are proper only when there is a complete absence of any evidence to warrant submission to a jury. Cities Service Oil Co. v. Laurey, 403 F.2d 537 (5th Cir. 1968). In this regard evidence and all inferences must be considered in the light most favorable to the party opposing directed verdict. Continental Air Lines v. Wagner Morehouse, 401 F.2d 23 (7th Cir. 1968). Some courts suggest that only evidence supporting the theories of the party opposing directed verdict may be considered. Dun & Bradstreet v. Miller, 398 F.2d 218 (5th Cir. 1968). Others suggest that directed verdict is proper only where there is a complete absence of the probative facts to support the jury verdict. Boeing Co. v. Shipman, 411 F.2d 365 (5th Cir. 1969). The fundamental idea in all this compels a Federal district trial court to exercise the greatest self-restraint in interfering with the constitutionally mandated processes of jury decision. The message is to do so only in the clearest of cases. This is manifestly not one of them.” 382 F.Supp. at 1348.
We agree with the legal philosophy articulated by Judge Allen Sharp in the Karczewski case. Recently this Court reversed a new trial granted to plaintiff, thereby reinstating a jury verdict in favor of defendant. In disapproving the trial judge’s preemptive order we said:
“To honor this action would create a bench supremacy and sap the vitality of jury verdicts.” Nelson v. Hartman, (1982), Mont., 648 P.2d 1176.
We agree with the sentiment expressed by Justice Black in a dissenting opinion filed in Galloway v. United States (1943), 319 U.S. 372, 63 S.Ct. 1077, 87 L.Ed. 1458, (Black, J., dissenting). Mr. Justice Black, in warning of possible [505]*505constitutional infringements inherent in the directed verdict or nonsuit, said:
“As for myself, I believe that a verdict should be directed, if at all, only when, without weighing the credibility of the witnesses, there is in the evidence no room whatever for honest difference of opinion over the factual issue in controversy. I shall continue to believe that in all other cases a judge should, in obedience to the command of the Seventh Amendment, not interfere with the jury’s function. Since this is a matter of high constitutional importance, appellate courts should be alert to insure the preservation of this constitutional right even though each case necessarily turns on its peculiar circumstances.” 319 U.S. at 407, 63 S.Ct. at 1096, 87 L.Ed. at 1480.
Applying the above articulated principle to the facts here, we cannot say that there is a complete absence of proof on proximate cause which would prevent plaintiff from having a jury resolution of his case. From the facts which we have detailed in this opinion, we hold that a jury of twelve reasonable people, could infer without resort to speculation, that the projectile which injured plaintiff came from the firing range near Deer Lodge. The jury was not compelled to accept the testimony of defendant’s expert witnesses. Rather, that testimony could properly be weighed against plaintiff’s circumstantial proof leaving the trier of fact free to make the factual determination. The jury has spoken, and regardless of how this Court would have decided the fact issues, we must affirm a verdict which we have found to be supported by substantial credible evidence.
IS PLAINTIFF’S RECOVERY LIMITED?
Appellants contend that exposure in this case is limited to applicable insurance limits by section 40-4402, R.C.M. 1947. The statute, adopted in 1963, provides as follows:
“Immunity defense prohibited when liability insured-reduction of award to policy limits. Whenever an insurer accepts any premium, money, or other consideration from a politicial subdivision of the state, municipality, or any pub-[506]*506lie body, corporation, commission, board, agency, organization, or other public entity for casualty or liability insurance, neither such insured nor insurer shall raise the defense of immunity from suit in any damage action brought against such insured or insurer, and any agreement in the insurance contract permitting the defense of immunity is hereby declared void ... If the court determines that the defendant could have successfully raised the defense of immunity, and if the verdict exceeds the limits of the applicable insurance, the court shall reduce the amount of such judgment or award to a sum equal to the applicable limit stated in the policy.”
The 1972 Montana Constitution, Article II, Section 18, provides:
“The state . . . shall have no immunity from suit for injury to a person or property, except as may be specifically provided by law by a % vote of each house of the legislature.”
The intent of section 40-4402 was to provide for waiver of sovereign immunity where insurance was carried but to limit such waiver to the limits of the liability policy. The statute itself contemplated the existence of governmental immunity which was abolished by the new constitution. The purpose of the statute is made clear by the title which provided:
“An act prohibiting the defense of sovereign immunity where public bodies are insured; . . . and providing for the reduction of award to policy limits where sovereign immunity defense could have been successfully raised; ...” Ch. 240, Laws of Mont. (1963).
Sovereign immunity could not be raised as a defense in this case. The statute has no application.
Section 2-9-104, MCA, limiting state liability, became law after this accident but was in effect at time of trial. Appellants contend section 2-9-104, MCA, is procedural and limits plaintiff’s recovery because it existed when judgment was rendered. This question was disposed of in Dvorak v. [507]*507Huntley Project Irrigation District (1981), Mont., 639 P.2d 62, 38 St.Rep. 2176. Damages are substantive and the measure of damage is governed by law in effect on the date of injury. The District Court order denying any limitation on plaintiff’s recovery is affirmed.
IS THE STATE EXEMPT FROM PAYING INTEREST FOR TWO YEARS?
Section 2-9-317, MCA, provides:
“No interest if judgment paid within two years. If a governmental entity pays a judgment within 2 years after the day on which the judgment may be assessed against the governmental entity.”
Plaintiff contends that this statute violates Article II, Section 18, of the 1972 Montana Constitution, which we have previously set forth, in that it has the effect of limiting the plaintiff’s recovery.
In Leaseamerica v. State (1981), Mont., 625 P.2d 68, 38 St.Rep. 398, we held that the constitutional provision abolishing governmental immunity did not render invalid the statute exempting the State from paying interest upon judgment. However, we based that decision upon the fact that the constitutional provision was intended to apply only to torts and that since the subject matter of Leaseamerica v. State was a contract, the constitutional provision had no application. We did not decide whether the State could be freed from paying interest on a tort judgment.
In the past this Court has treated interest as something apart from the cause of action. In Stanford v. Coram (1903), 28 Mont. 288, 72 P. 655, the Court said:
“. . . The judgment is itself a creation of law. It bears no interest unless granted by legislative enactment. . . A party is not entitled to interest merely because he has a judgment, but solely because the legislature, in its discretion, has said he may charge interest.” 28 Mont, at 292, 72 P. at 655.
This Court has also stated that interest is damage for delay in payment of the principle obligation. See State High[508]*508way Commission v. Marsh (1978), 175 Mont. 460, 575 P.2d 38.
We hold that interest on a judgment is not an integral part of the case of action itself. We find that section 2-9-317, MCA, does not offend Article II, Section 18, of the Montana Constitution. We do not here decide whether the State can be treated differently from other tort-feasors concerning the subject of damages which are part of the cause of action itself. We rather hold that interest, not being a detriment arising from the wrongful act, can be suspended by statute as was done here.
The judgment of the District Court is affirmed in its entirety.
MR. CHIEF JUSTICE HASWELL and JUSTICES DALY, WEBER and SHEEHY, concur.