Okla. Stat. tit. 12, § 12-2303: Effect of presumptions in civil cases

Except when otherwise provided by law, when the basic fact of a

presumption has been established as provided in Section 302 of this

Code:

1. If the basic fact has any probative value of the existence

of the presumed fact, the presumed fact shall be assumed to exist

and the burden of persuading the trier of fact of the nonexistence

of the presumed fact rests on the party against whom the presumption

operates; or

2. If the basic fact does not have any probative value of the

existence of the presumed fact, the presumed fact is disregarded

when the party against whom the presumption operates introduces

evidence which would support a finding of the nonexistence of the

presumed fact and the existence of the fact otherwise presumed is

then determined from the evidence in the same manner as if no

presumption had been operable in the case.