2,028. A Legal Presumption of Relationship
Hilchos Issurei Biah 1:19
The witnesses to prohibited relations don’t have to see the actual insertion. Rather, once they see the couple embracing in the manner of those who engage in intimacy, they may be executed based on this evidence. We don’t say that perhaps he didn’t insert the tip because the legal presumption is that in this position, he did.
Hilchos Issurei Biah 1:20
If a presumption has been established that certain people are close relatives, we judge on that basis even in the absence of proof of their relationship. The courts can give lashes and execute by burning, stoning and strangulation based on this presumption. Therefore, if it has been accepted that a certain woman is a man’s sister, daughter or mother and he was intimate with her in front of witnesses, then he is lashed or executed by burning or stoning even though there is no absolute proof of their relationship. It once happened that a woman came to Jerusalem with an infant whom she raised under the presumption that he was her son. They subsequently were intimate and she was brought to court and executed by stoning. Proof that we rely on such presumptions is seen from the fact that the Torah speaks of execution for one who curses or strikes his father, even though there is no absolute proof that this is his father. Rather, we operate under existing presumptions. The same is also true regarding other relatives.