Is the evidence admissible?
"It varies from state to state, but for the most part, it's likely to be admissible, since the party offering the evidence -- their wives -- would have what's called 'clean hands,' meaning that they would not have engaged in any elicit or improper behavior -- instead, that was the action of the third party. There are a few states that probably would exclude [the evidence], but the majority of sates will permit it. The question becomes, what is its relevance?"
What would make the evidence relevant?
"It's often relevant, but in ways people might not expect. Most states have adopted a sort of 'no-fault' perspective to divorce. As a result, most states don't punish people in terms of property division or maintenance for marital misconduct. But, courts in virtually all states are willing to consider martial misconduct when it involves a misuse or dissipation of the party's assets -- so to the extent that any money has been used to pursue this relationship... courts will be interested."