John McLean

“ Dunn, 6 Peters 51. In that case the court said, 'it is a well settled principle, that no person who is a party to a negotiable instrument, shall be permitted, by his own testimony, to invalidate it.' And this doctrine is sustained by reason and authority. ”

“ If an individual whose name appears upon the face of a negotiable instrument, either as drawer, indorser or acceptor, shall be a competent witness to prove facts or circumstances which lessen or destroy its value, before or at the time he gives it currency, the credit of commercial paper could not be sustained. The rule laid down in 1 Term Rep. 296, on this subject is a sound one, and was sanctioned by this court in the case above cited.
On the part of the defendant in error, it is contended, that the witness objected to was not the only witness in the case ”