Perhaps you've seen news of this pleading, which Jacob Gershman reported in the WSJ Law Blog (with a link):
http://blogs.wsj.com/law/2015/01/02/dershowitz-im-an-innocent-victim-of-an-extortion-conspiracy/
My question is hypothetical: Let's assume that the accusation is false. (I must say I don't believe it.) The litigation privilege is traditionally an absolute defense to a defamation action and I assume it is so in Florida. The lawyers may be subject to Rule 11-type sanctions depending on their factual basis for the statement if indeed it is false. But would they also be subject to professional discipline?
The obvious rule is Rule 3.1. Would it be a complete defense to a Rule 3.1 charge that the client made this accusation and was consistent in the details of her story? Or does a factual investigation require more given the gravity of the accusation and the fact that the alleged events occurred six years ago? The more could be a lie detector test and investigation for corraborating details. Or is the gravity of the claim irrelevant to the Rule 3.1 obligations?