Truth is always a defense to a defamation suit. The problem sufaces if the allegations contained the court pleadings are false. The litigants are protected by a qualified privilege in so far as what they say in their pleadings or testimony. However the privlege can be lost through overpublication beyond the intended purpose of the privilege. Non-litigants are not protected by the privilege, and may be sued for defamation if they repeat the false allegations to third parties.

We had a case hear in Connectuct several years ago in which exactly that happened. It was a messy divorce case, and somehow the statements of one of the litigants was published and the privilege was lost to that litigant