The appellate courts have long held that the employee must prove the nature and extent of any disability by a reasonable degree of certainty. ${ }^{1}$ Downing v. Willamette Industries, Inc., 895 S.W.2d 650, 655 (Mo. App. 1995); Griggs v. A. B. Chance Company, 503 S.W.2d 697, 703 (Mo. App. 1974). Such proof is made only by competent and substantial evidence. It may not rest on speculation. Idem. Expert testimony may be required where there are complicated medical issues. Goleman v. MCI Transporters, 844 S.W.2d 463, 466 (Mo. App. 1993); Griggs at 704; Downs v. A.C.F. Industries, Incorporated, 460 S.W.2d 293, 295-96 (Mo. App. 1970).
Section 287.020.3(1) Mo. Rev. Stat. (2005 Supp.), which was added in 2005, provides in pertinent part that "[a]n injury by accident is compensable only if the accident was the prevailing factor in causing both the resulting medical condition and disability." "Prevailing factor" is defined as "the primary factor, in relation to any other factor, causing both the resulting medical condition and disability."
Section 287.190.6(2) Mo. Rev. Stat. (2005 Supp.), which was added in 2005, provides that "[p]ermanent partial disability or permanent total disability shall be demonstrated and certified by a physician. Medical opinions addressing compensability and disability shall be stated within a reasonable degree of medical certainty. In determining compensability and disability, where inconsistent or conflicting medical opinions exist, objective medical findings shall prevail over subjective medical findings. Objective medical findings are those findings demonstrable on physical examination or by appropriate tests or diagnostic procedures."
The appellate courts have long held that the fact finder may accept only part of the testimony of a medical expert and reject the remainder of it. Cole v. Best Motor Lines, 303 S.W.2d 170, 174 (Mo. App. 1957). Where the opinions of medical experts are in conflict, the fact finding body determines whose opinion is the most credible. Hawkins v. Emerson Electric Co., 676 S.W.2d 872, 877 (Mo. App. 1984). Where there are conflicting medical opinions, the fact finder may reject all or part of one party's expert testimony which it does not consider credible and accept as true the contrary testimony given by the other litigant's expert. Webber v. Chrysler Corp., 826 S.W.2d 51, 54 (Mo. App. 1992); Hutchinson v. Tri-State Motor Transit Co., 721 S.W.2d 158, 163 (Mo. App. 1986). The provisions of Section 287.190.6(2) have probably modified the unfettered discretion previously given to the fact finder in accepting or rejecting expert opinions to the extent that the fact finder must now accept those opinions which are based on objective findings and reject inconsistent opinions based on subjective findings.
However, where the facts are within the understanding of lay persons, the employee's testimony or that of other lay witnesses may constitute substantial and competent evidence of the nature, cause, and extent of disability. Silman v. William Montgomery \& Associates, 891 S.W.2d 173, 175 (Mo. App. 1995). This is especially true where such testimony is supported by some medical evidence. Pruteanu v. Electro Core Inc., 847 S.W.2d 203 (Mo. App. 1993); Reiner v. Treasurer of State of Mo., 837 S.W.2d 363, 367 (Mo. App. 1992); Fisher v. Archdiocese of St. Louis, 793 S.W.2d 195, 199 (Mo. App. 1990); Ford v. Bi-State Development Agency, 677 S.W.2d 899, 904 (Mo. App. 1984); Fogelsong v. Banquet Foods Corp, 526 S.W.2d 886, 892 (Mo. App. 1975). The trier of facts may even base its findings solely on the testimony of the
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[^0]: 1 It is unclear whether this standard has been changed by the adoption of Section 287.808 Mo. Rev. Stat. (2005 Supp.) which modified the burden of proof for factual propositions to "more likely to be true than not true."
employee. Fogelsong at 892 . The trier of facts may also disbelieve the testimony of a witness even if no contradictory or impeaching testimony is given. Hutchinson v. Tri-State Motor Transit Co., supra at 161-2; Barrett v. Bentzinger Brothers, Inc., 595 S.W.2d 441, 443 (Mo. App. 1980). The uncontradicted testimony of the employee may even be disbelieved. Weeks v. Maple Lawn Nursing Home, 848 S.W.2d 515, 516 (Mo. App. 1993); Montgomery v. Dept. of Corr. \& Human Res., 849 S.W.2d 267, 269 (Mo. App. 1993). The provisions of Section 287.190.6(2) have probably modified the unfettered discretion previously given to the fact finder in accepting or rejecting lay opinions to the extent that the fact finder must now reject lay opinions which conflict with medical opinions based on objective findings.
The determination of the degree of disability sustained by an injured employee is not strictly a medical question. While the nature of the injury and its severity and permanence are medical questions, the impact that the injury has upon the employee's ability to work involves factors which are both medical and nonmedical. Accordingly, the appellate courts have repeatedly held that the extent and percentage of disability sustained by an injured employee is a finding of fact within the special province of the Commission. Sellers v. Trans World Airlines, Inc., 776 S.W.2d 502, 505 (Mo. App. 1989); Quinlan v. Incarnate Word Hospital, 714 S.W.2d 237, 238 (Mo. App. 1986); Banner Iron Works v. Mordis, 663 S.W.2d 770, 773 (Mo. App. 1983); Barrett v. Bentzinger Brothers, Inc., 595 S.W.2d 441, 443 (Mo. App. 1980); McAdams v. Seven-Up Bottling Works, 429 S.W.2d 284, 289 (Mo. App. 1968). The fact finding body is not bound by or restricted to the specific percentages of disability suggested or stated by the medical experts. It may also consider the testimony of the employee and other lay witnesses and draw reasonable inferences from such testimony. Fogelsong v. Banquet Foods Corporation, 526 S.W.2d 886, 892 (Mo. App. 1975). The finding of disability may exceed the percentage testified to by the medical experts. Quinlan v. Incarnate Word Hospital, at 238; Barrett v. Bentzinger Brothers, Inc., at 443; McAdams v. Seven-Up Bottling Works, at 289. The uncontradicted testimony of a medical expert concerning the extent of disability may even be disbelieved. Gilley v. Raskas Dairy, 903 S.W.2d 656, 658 (Mo. App. 1995); Jones v. Jefferson City School Dist., 801 S.W.2d 486 (Mo. App. 1990). The fact finding body may reject the uncontradicted opinion of a vocational expert. Searcy v. McDonnell Douglas Aircraft Co., 894 S.W.2d 173, 177-78 (Mo. App. 1995).