Section 13.3 Scope of Expert Testimony Compared to Lay Testimony

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B. (§13.3) Scope of Expert Testimony Compared to Lay Testimony

“Allowing an expert to give an opinion upon a subject of inquiry, instead of requiring that the witness give only facts, is an exception to the general rule that witnesses must state facts. . . . An expert witness, in a manner, discharges the functions of a juror . . . .” Housman v. Fiddyment, 421 S.W.2d 284, 289 (Mo. banc 1967) (emphasis added). The exception is made as a matter of necessity:

“If laymen . . . are not to be guided on issues requiring peculiar and thorough special training in a science or art beyond the experience and knowledge common to mankind by witnesses possessing the necessary testimonial qualifications, juries will be cast into a river of doubt and must establish an arbitrary standard of their own founded upon conjecture and surmise in their effort to reach certain and sure ground.”

Fisher v. Wilkinson, 382 S.W.2d 627, 632 (Mo. 1964) (quoting Pedigo v. Roseberry, 102 S.W.2d 600, 607 (Mo. 1937)). Through the ability to...