Rule 630 The presumptions established by this article, and all other rebuttable presumptions established by law that fall within the criteria of Section 603, a…

When a law creates a certain type of presumption, it shifts who has to bring up evidence in court. Instead of one side having to prove something from scratch, the other side must come forward with evidence to counter what the law already assumes to be true.

For example, if a law presumes that a mailed letter was received, the person arguing it was never received has to produce evidence showing that. The presumption does the initial work, and the other side must respond to it.