(dissenting) — I agree with the majority that the issue is "whether the medical testimony was sufficient to sustain a finding by the Board and by the jury that the petitioner's hepatitis was attributable to her employment." Put another way, the question is whether there is a causal connection between petitioner's illness and her employment. I also agree with the majority that the causal connection between petitioner's physical condition and her employment must be established by medical testimony based upon probabilities rather than mere possibilities. Consequently, if petitioner fails to establish by medical testimony that the disease is probably related to her employment, she cannot recover.
In an effort to reach the desired result, the majority has tolerated too many legal and factual gaps in logic. They *638have acknowledged the basic rules only to studiously circumvent them. Therefore, I must dissent.
While they initially acknowledged petitioner's burden, the majority retreats from that acknowledgment by suggesting medical opinion is not necessary on the ultimate issue in all cases. It is said to be sufficient that medical testimony merely "shows the causal connection." Thus, the majority suggests a causal connection may be established by inference, leaving the unwarranted implication that the required proof may be somewhat less if an inference is involved. This, of course, is incorrect. The proposition is not even supported by the majority's case citation. In fact, the cited case makes it abundantly clear a claimant may recover only "where a causal connection between an industrial injury and a subsequent physical condition is established, with at least some degree of probability.” (Italics mine.) Seattle-Tacoma Shipbuilding Co. v. Department of Labor & Indus., 26 Wn.2d 233, 242, 173 P.2d 786 (1946). See also Sawyer v. Department of Labor & Indus., 48 Wn.2d 761, 296 P.2d 706 (1956). The evidence must be of sufficient probative value to remove the question of causal relation from the field of speculation and surmise. The evidence must present something more than a mere possibility or conjecture. Seattle-Tacoma, 26 Wn.2d at 242. As stated by that case at page 241:
The general rule, from which this court has never deviated, is stated in 135 A. L. R. 517, as follows:
"It appears to be well settled that medical testimony as to the possibility of a causal relation, between a given accident or injury and the subsequent death or impaired physical or mental condition of the person injured is not sufficient, standing alone, to establish such relation. By testimony as to possibility is meant testimony in which the witness asserts that the accident or injury 'might have,' 'may have,' or 'could have' caused, or 'possibly did' cause the subsequent physical condition or death or that a given physical condition (or death) 'might have,' 'may have,' or 'could have' resulted or 'possibly did' result from a previous accident or injury — testimony, that is, which is confined to words indicating the possibility or *639chance of the existence of the causal relation in question and does not include words indicating the probability or likelihood of its existence."
The subtle but significant change in the burden of proof, for which the majority opts, is not based on any past or current law of this state. Rather, it stems from a series of foreign cases based on philosophical underpinnings which the majority claims better serve the spirit and intent of the industrial insurance act of this state. I totally disagree.
The majority does not claim, and my review does not establish, that the industrial insurance laws of the foreign jurisdictions relied on are the same or even similar to our own. In fact, from as early as Stertz v. Industrial Ins. Comm'n, 91 Wash. 588, 604, 158 P. 256 (1916) to as late as Thompson v. Lewis County, 92 Wn.2d 204, 208-09, 595 P.2d 541 (1979) we consistently have held that our industrial insurance act is unique and that the opinions of other states' courts are of little assistance as an interpretive medium. Yet, without overruling a single case, the majority would have us abandon the basic burden of proof long accepted in this jurisdiction. They would have us make this important change based upon opinions of a few foreign jurisdictions. By the proposed subtle change in emphasis the kind of evidence necessary to sustain a claimant's burden of proving the causal connection between a disease or injury and employment would be changed. However subtly accomplished, I cannot agree with the change or the foreign cases cited in support.
I am also concerned by the undue emphasis the majority places upon the medical testimony of two doctors. While their testimony will be discussed more fully later, it is sufficient to say at this point that the testimony is accepted uncritically with the oversimplistic view that the findings and decision of the Board, having been accepted by the jury, must be deemed correct. This view ignores the fact that important medical testimony considered by the Board was stricken by the trial court thus never reaching the jury.
*640The striking of such testimony brings into play a second portion of the rule on prima facie correctness of Board findings and decisions. The rule does not apply where there is no evidence to support an essential part of the claim. This rule prevents the fiat of the Board from being substituted for evidence. There must be substantial evidence to support the Board before its findings and decision are deemed prima facie correct. Jepson v. Department of Labor & Indus., 89 Wn.2d 394, 401, 573 P.2d 10 (1977), see also the numerous supporting cases cited therein at page 401. Consequently, we must return to the issue as originally framed by the majority and examine critically the medical testimony furnished by the two doctors. The ultimate question is whether the medical testimony that actually reached the jury is sufficient to sustain a finding by the jury that petitioner's hepatitis was causally connected to her employment. This question must be answered in the negative.
The majority emphasizes the fact that Dr. Carrado testified in the Board record that the odds were overwhelmingly in favor of the claimant having contracted the disease at the hospital (her place of employment). As acknowledged by the majority, however, the statement was made in answer to a hypothetical question which assumed that another nurse at the hospital had hepatitis. This fact was never established at the Board hearing, however. Since the hypothetical question assumed evidence never established, the trial court struck the entire question and answer thereto.2 Thus, contrary to the majority's view, the statement by Dr. Carrado, upon which the majority relies, never did reach the jury. I grant that on motion for a new trial the judge apparently had second thoughts and wondered whether it might have been better to let a portion of the *641doctor's testimony stand rather than having excluded it. But, it was stricken and no one actually has contended on appeal that all or any part of the answer to the hypothetical question should have gone to the jury. Since no error has been assigned, that issue is not before us. Consequently, we are faced with the accomplished fact that none of the doctor's testimony on causal connection was heard by the jury.
The testimony of Dr. Carrado having failed to establish the necessary causal connection between petitioner's disease and her employment, the only remaining source of medical proof was Dr. Stacey. The majority has conceded Dr. Stacey "refused to give a direct opinion as to the probability that she contracted the disease at the center." The majority seems to suggest, however, that the so-called refusal stems from his having misunderstood the question. Whether this assumption is correct or incorrect is irrelevant. The fact remains that, whatever the reason, Dr. Stacey did not establish any causal connection. In fact, Dr. Stacey's position went beyond the mere "refusal" mentioned by the majority. The doctor's statement was actually a positive disclaimer that any logical causal connection existed. He testified as follows:
In the case of Norma Jean Carrado I think it is conjecture as to whether she obtained her hepatitis from a patient on her job in some way in the hospital or from the outside . . . it's impossible to determine in a single instance the mode by which any person develops hepatitis.
(Italics mine.) While the doctor acknowledged that the risks of getting hepatitis had been shown to be greater in hospital dialysis personnel than in the general public, he went on to say, in the case of Mrs. Carrado (and it is, after all, her case that is before the court):
In this case I do not think there is any way to determine whether the lady's hepatitis was contracted within or out of the hospital.
*642As a result it is clear there was an absence of medical evidence to establish the necessary causal connection. Moreover, Dr. Stacey's testimony established absolutely that it was impossible to make the causal connection in Mrs. Carrado's case.
As a last resort, the majority points to the fact that hepatitis may be contracted from undetectable carriers. Thus, it is said to be inferable from the nature of her work, she in fact did contract it from such a carrier in the hospital. While this gap in logic actually begs the question, the majority attempts to jump the gap by asserting that the industrial insurance act "is to be liberally applied to achieve its purpose of providing compensation to all covered persons injured in their employment."
I agree with the foregoing general statement of the law. However, I disagree with the majority's application of it in this case. As we said in Ehman v. Department of Labor & Indus., 33 Wn.2d 584, 595, 206 P.2d 787 (1949):
that rule does not apply to questions of fact but to matters concerning the construction of the statute, and that the principle does not dispense with the requirement that those who claim benefits under the act must, by competent evidence, prove the facts upon which they rely.
(Italics mine.) There is no such competent medical evidence in the record. The mere fact that an issue is difficult to establish does not lessen or change the burden of proof.
In sum, there is no medical testimony in the record upon which the jury could have based a determination that petitioner's hepatitis was causally connected with her employment. The Court of Appeals should be affirmed.
Brachtenbach and Horowitz, JJ., concur with Stafford. J.The Board record used by the trial judge shows clearly at pages 64-68 that he wrote on the record in pencil that the objection to the hypothetical question was sustained and in addition crossed out all of the offending material. This includes the statement, "The odds are overwhelmingly in favor of it.”