dissenting:
The first ground upon which I would reverse and grant a new trial of this cause is the impropriety of admitting evidence of the experiment by Pam Boyle, and her opinion based upon that experiment as to the length of time that Mark Johnson was under water, deprived of oxygen.
Pam Boyle’s testimony of the near drowning incident begins with herself being in the pool hanging onto the edge, *48approximately half way between the two ends on the side of the pool away from the boys’ locker room. While she was there a young boy swam up to her and informed her that a boy had drowned. She then saw Missy Blais and another boy bringing Mark Johnson from the water somewhere in the middle of the pool. She went to them, took Mark Johnson from Missy Blais, and immediately started to administer mouth-to-mouth resuscitation. She stated, probably truthfully, that she had saved Mark Johnson’s life.
After the incident, Pam staged a series of races among several boys involving a rubber ring and a ten-pound weight for the purpose of determining how long Mark Johnson was under the water. According to her testimony, these tests demonstrated that Mark was under water only thirty seconds. She was allowed to testify to that conclusion as a fact.
Based on her observation, her opinion as to the result of the experiment, limiting Mark’s underwater experience to thirty seconds, was clearly irrelevant. She did not establish, and no other witness established, how long Mark Johnson had been under the water before he was discovered and brought to the surface by Ms. Blais and the boy. At the most the races or games, conducted after the incident, only showed how long it would take boys, diving and swimming, to retrieve a rubber ring or a diving bell from under the water. As a matter of fact, the boys were unable to retrieve the diving bell.
It was, of course, impossible to establish that Pam Boyle was an expert as to how long Mark was under the water prior to being brought to the surface. It takes actual observation, not expertise, to establish such a fact. She did not have the actual observation.
The rule applicable to the admissibility of the opinion of an expert witness in Montana, until now has been that if his opinion is unsupported by the details of his measurements or observations, both as to the date upon which they are based and the manner of reaching the result, his opin*49ion is not competent or relevant. When he gives the details it is a question of law whether his method was correct, and a question of fact as to whether his result was correct. Irion v. Hyde (1940), 110 Mont. 570, 105 P.2d 666. The rule in Irion applies with special force in this case:
“A witness, of special knowledge or skill on a subject outside of the ordinary realm of human experience, may be permitted to state his inference, from facts observed by him, as to matters connected with his specialty, not only because of the frequent difficulty of communicating the facts to the jury but also because, even if the facts could be fully laid before them, they would not possess the special knowledge or training necessary to coordinate and weigh the facts so as to draw the correct and proper inference therefrom. Such a witness is frequently termed an expert, but this is inaccurate, for the skilled witness testifies to the result of his own observation, and occupies the same position as any other witness except that within certain lines he possesses a superior knowledge which enables him to understand, as one without such special knowledge could not, what he has observed, although he may also be competent to testify as an expert upon hypothetically stated facts. . . a
“. . . the judgment of an expert, when opposed to undisputed facts and the dictates of common sense, will not support a verdict, and the court should not permit the jury to be influenced by evidence on which they could not, within the laws of correct reasoning, make the finding. . . a
“The reasons for rejecting a conclusion become stronger where it is apparent that it cannot reasonably be reached on the facts which are claimed to support it, where such facts are themselves the result of inference, or where the conclusion is not a necessary one. . .” 110 Mont. at 577-578, 105 P.2d at 671. (Emphasis added; citations omitted.)
The evidence of this professed expert, not being based upon her knowledge, observation, or an inference of fact *50reasonably derived from other facts, was compounded when her opinion as to length of time that Mark Johnson was under the water was used as a basis by defense medical witnesses to testify that he could not have suffered oxygen deprivation. Her opinion flies in the face of her observed condition of the boy following his rescue, that his lips were blue, and of an independent witness, who observed that the boy’s face was blue. In fact, in a later-discovered letter that Pam Boyle herself had written to defense counsel, she stated, “Mark’s face was very blue and I got no response after slapping his face.”
The staged races among the boys could never be a basis for her opinion as to how long Mark was under water when no observation existed to support the conclusion given.
Secondly, this case should be reversed because of the failure by defense to comply with pretrial discovery rules.
On the day before the trial, counsel for defense moved the court to add four witnesses to the list of proposed witnesses in the trial. One of these names, Pam Boyle, turned out to be a critical witness in the cause. The other three witnesses had not been identified to plaintiff’s counsel in any pretrial discovery beforehand, although seasonably plaintiff had requested in interrogatories the names and addresses of all witnesses having any knowledge of the pertinent facts of the incident.
The situation with Pam Boyle is particularly disturbing. Her address given by the defense in their response to the interrogatories was her parent’s home, but in fact this was not her true address. It was discovered at the time of the motion for new trial, when the defense was required by the court to “cough-up” a letter it had received from Pam Boyle before the trial, that defense counsel did in fact have her address, and that she was residing in Omaha, Nebraska. Miss Boyle wrote a letter to the law firm, in which she stated some facts that are certainly now at variance with what she testified at the trial. In her letter she states:
“. . .1 was somewhere in the shallow end when Mark re*51quested permission to go to the bathroom. Permission was given.
“A short time later (I have no idea of the exact time) Joey and another boy were shouting at me across the pool and Missy, a junior counselor, brought Mark to me. I was by the side, somewhere between the three and five foot mark on the right side of the pool.
“Mark’s face was very blue and I got no response after slapping his face. . .”
It will be seen from the contents of her letter to counsel, apparently some period of time before the trial, that Pam Boyle had no basis upon which she could estimate the period of time that Mark Johnson had been under water. Because of the failure of defense counsel, whether purposely or inadvertently is unimportant, to divulge the true address in response to the interrogatories of Pam Boyle, plaintiff was deprived of this most important information.
Plaintiff, immediately before trial, made a motion in limine that Pam Boyle and the other three witnesses not be allowed to testify because of the failure of defense counsel to abide by the pretrial discovery rules. The court refused that motion, and offered instead to allow interviews of the witnesses on the day of the trial, and offered to continue the cause if necessary. The offer to continue the cause was declined several times by plaintiff’s counsel, they relying on their belief that under Montana law, the testimony of the witnesses should not be allowed at all because of the failure of defense counsel to provide the pertinent information in accordance with pretrial discovery rules.
The Montana Rules of Civil Procedure provide a positive duty on the part of the party responding to interrogatories to supplement the same to include information thereafter acquired. Rule 26(e)(2), M.R.Civ.P., provides:
“A party is under a duty seasonably to amend a prior response if he obtains information upon the basis of which (A) he knows that the response was incorrect when made, or (B) he knows that the response though correct when *52made is no longer true and the circumstances are such that failure to amend the response is in substance a knowing concealment.” (Emphasis added.)
At the time of the receipt by defense counsel of the letter from Pam Boyle, mailed from Omaha, Nebraska, the defense counsel knew that the response that they had made respecting her address was incorrect. Under the language of our Rule 26, whether their failure to disclose the correct address was purposeful or inadvertent, the legal effect is that it is a “knowing concealment.” The same rule applies to the witnesses which were not divulged until the day before trial, other than Pam Boyle.
In Sanders v. Mount Haggin Livestock Company (1972), 160 Mont. 73, 500 P.2d 397 (Mr. Chief Justice Haswell and Mr. Justice Daly dissenting), this Court on nearly the same details, held it reversible error for a trial court to allow witnesses to testify whose location had not been made known to the other party:
“This situation justified and required the exclusion of the witnesses’ testimony. A motion to exclude and disallow any testimony of these witnesses was made, supported, and elaborated upon with a complete statement of the surrounding facts. The trial court was in error to refuse this sanction for failure to make proper and accurate responses to interrogatories that were designed to elicit exactly the information which was withheld.” 160 Mont. at 82, 500 P.2d at 402.
It is not an answer to this issue that plaintiff’s counsel themselves never identified in interrogatory answers an expert, Vern Cherewatenko, as being an expert or a witness. Two wrongs do not make a right, and we are not here considering whether prejudice resulted to the defense from the failure to divulge information about Cherewatenko. The issues should easily have been resolved at the District Court level by an evenhanded ruling from the District Court that the undisclosed witnesses presented by either party would not be allowed to testify when the pretrial discovery process *53was abused.
It is my belief, since I subscribe to full disclosure of law and facts at all stages of the trial, that the purpose of the Rules of Civil Procedure is best served when lawyers are fully candid with fellow lawyers and the courts. By insisting on the integrity of discovery under the rules, we open up the facts, encourage settlements, and avoid protracted litigation. These were the promises held out by members of this Court when they came to the legislature in 1963 to get authority to adopt the federal rules of procedure for Montana. Since Sanders v. Mount Haggin, supra, this Court has shown some spine in insisting on the integrity of the discovery process. Owen v. F.A. Buttrey Co. (1981), Mont., 635 P.2d 978, 38 St.Rep. 1588; Kuiper v. District Court (1981), Mont., 632 P.2d 694, 38 St.Rep. 1288. There is no reason to step back now from requiring forthright candor in the discovery process.