I want to know if the consent of a person is taken during he is i

My father and his brothers have mortgaged the property under mortgage with a conditional sale for Rs 30000 for that they accepted Rs 15000 for the same.But eventually, the mortgagee (father and son)sold the same property ,with the contradictory claim that they have bought this land ,to other parties with the contradictory claim of partitioning the said land.Father sold some portion to one party and son sold the portion to other different party.This was happened during the condition embodied in the document of Mortgage by conditional sale.So we filed suit to entitle us with the redemption of mortgage land on payment.During the pending of the suit, the party to which the father(mortgagee) allegedly filed a criminal case of outraging modesty of neighbor where my father(accused) were acquitted by the court.But the issue here is that when he was in the custody of the police for above false case, the party to which the mortgagee sold had taken consent of my father for his transaction in the police custody.So,I want to know if the consent of a person is taken during he is in the custody of police is legal or not?