From: Rabbi Moshe Sofer
To: Rabbi Moshe Perles
A man with a missing brother sought to marry with a conditional kiddushin that would be retroactively voided if the brother could not be located for chalitzah. The Chasam Sofer ruled leniently, permitting the conditional kiddushin based on his own teachers' tradition and his prior practice in Mattersdorf, endorsing the Me'il Tzedakah and Beis Meir against those who wished to be stringent. He further innovated that the proceedings should be recorded as a formal beis din ruling rather than witness testimony, avoiding the problem of relying on written testimony after the original witnesses have died.
Source: Shu"t Chasam Sofer EH I §110