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.