When the testimony of a subscribing witness to a deed or of the magistrate who took the acknowledgment thereof has been taken in the trial of any civil action in relation to the execution, delivery or registry of such deed, and such witness has since died, proof of such former testimony is admissible in the trial of any other civil action involving the same question if the parties are the same or if one of the parties is the same and the adverse party acted as agent or attorney for the adverse party in the former action, but such testimony may be impeached like the testimony of a living witness.