A man is forbidden to his father's wife, even if she is not his biological mother (cf: Leviticus 18:8; Yevamot 1:3). Is this still the case after his father dies or after he divorces her? In other words, is a man prohibited to his father's widow or to his father's divorcee?
[For anybody unfamiliar with the language of such regulations, this is a technical question about prohibited sexual relationships only. I am asking this out of a desire to understand the halakha, and am offering neither approval nor censure.]