Responsa for Bekhorot 97:32

דכולי עלמא

IF THE FATHER, HOWEVER, DIES AFTER THIRTY DAYS, IT IS UNDER THE PRESUMPTION OF HAVING BEEN REDEEMED UNTIL HE [THE SON] IS TOLD THAT HE WAS NOT REDEEMED.<span class="x" onmousemove="('comment',' Until the son is informed that the father had said before he died that he had not redeemed him. There is no need for proper witnesses here and a mere statement of not having redeemed suffices, since the presumption that the father had redeemed is not a very strong one, people as a rule not hastening to pay their debts immediately when due. It is not relevant here to say until the priest brings proof that the redemption money had not been paid, for even if he does the son can still maintain that his father gave the five sela's to some other priest.');">²⁸</span>

Teshuvot Maharam