From: Rabbi Moshe Sofer
To: Rabbi Leib
The Chasam Sofer rules that lechatchilah three mutually unrelated qualified judges should oversee a get, since the current practice of validating witnesses' signatures constitutes kabbalas eidus requiring a proper beis din. However, bedi'eved a get arranged before fewer or disqualified judges is not invalidated. For chalitzah, related judges may never serve together, and communal acceptance of disqualified judges cannot bind orphans or outsiders.
Source: Shu"t Chasam Sofer EH II §64