42 Pa.C.S. § 5932: Witness competent to testify against interest; to become competent upon release of interest.

Any person who is incompetent under section 5930 (relating to surviving party as witness, in case of death, mental incapacity, etc.) by reason of interest may nevertheless be called to testify against his own interest, and in that event he shall become a fully competent witness for either party. Such person shall also become fully competent for either party by filing of record a release or extinguishment of his interest.