The legal estate conveyed to a mortgagee, his heirs and assigns, or to a trustee to secure a debt, his heirs and assigns, shall be construed and held to be a qualified fee simple, determinable upon the release of the mortgage or deed of trust, as hereinafter provided, or the appointment of a new trustee by agreement of the parties pursuant to § 42-814(b) or by judicial decree for the causes hereinafter mentioned; provided, that nothing in this section contained shall prevent the passing of an absolute and unqualified estate in fee simple under a deed made by the mortgagee, trustee, or new trustee in pursuance of the powers conferred by the mortgage or deed of trust.
D.C. Code § 42-803