From: Rabbi Moshe Sofer
To: Rabbi Aryeh Yehuda Leib Toiber
When a young man died before marrying his betrothed, the Chasam Sofer rules that his heirs may recover the engagement gifts sent to the bride: items still extant at the time she learned of his death are returned in full, items consumed after she learned of the death are repaid at full value, and items consumed before she heard the news are subject to a one-third deduction with two-thirds repaid. The heirs may request a general cherem to verify the bride's account, but may not impose a personal oath on her, as she is believed through a migu.
Source: Shu"t Chasam Sofer EH I §128