Rule 606 The effect of a presumption affecting the burden of proof is to impose upon the party against whom it operates the burden of proof as to the nonexiste…

When a legal presumption applies in a case, the other side has to prove it wrong. This is different from just raising a doubt about it.

For example, if the law presumes something to be true, the person arguing against that presumption cannot simply say "maybe it's not true." They have to actually prove, with evidence, that the presumed fact does not exist. The burden of proof shifts fully to them.