He does apparently have a conflict: if he is being called as a fact witness to testify about the siging or notarization, then his own interests could easily conflict with his duties as an attorney, since if something was done wrong in the signing or execution, he would likely have to lie to protect himself--or he tells the truth as a witness to avoid perjury, but doing so may hurt his client's case. He cannot necessarily simultanously be a truthful fact witness and also a strong advocate for his client.However, other people cannot raise a conflict--only the client can. If the client (the husband) is willing to have his lawyer also be called as a witness against him, he can do so. It is the husband who could raise the issue of conflict if he wanted a different attorney. Other people cannot raise the conflict for him or use it to disqualify his lawyer.