The legislature defined the prevailing factor for us. "The prevailing factor" means, "the primary factor, in relation to any other factor, causing both the resulting medical condition and disability." §287.020.3(1). The phrase "prevailing factor" appears in two different subsections of $\S 287.020$. The context of the subsections reveals that the phrase is used in two different ways.
- $\S 287.020 .3(1)$ provides that, "[a]n injury by accident is compensable only if the accident was the prevailing factor causing both the resulting medical condition and disability."
- $\S 287.020 .(2)$ provides that, "[a]n injury shall be deemed to arise out of and in the course of the employment only if: (a) It is reasonably apparent, upon consideration of all the circumstances, that the accident is the prevailing factor in causing the injury; and,... "
Substituting the definition of "prevailing factor" for each occurrence of the phrase "prevailing factor" does not cut an easy path to a compensability determination. Substituting the definition in §287.020.3(1) produces the following redundant requirement:
An injury by accident is compensable only if the accident was [the primary factor, in relation to any other factor, causing both the resulting medical condition and disability] causing both the resulting medical condition and disability.
Substituting the definition in §287.020.3(2) produces the following somewhat unintelligible requirement:
An injury shall be deemed to arise out of and in the course of the employment only if: (a) It is reasonably apparent, upon consideration of all the circumstances, that the accident is [the primary factor, in relation to any other factor, causing both the resulting medical condition and disability] in causing the injury; and,...
The meanings of the amendments are far from clear. To be compensable, must the accident be the primary factor, in relation to any other factor, in causing the injury? In causing both the resulting medical condition and disability? In causing the injury, the resulting medical condition, and the disability? In the present case, employee has shown the accident caused all three so I will not ponder that ambiguity further.