McClure had sold Porter a slave, Hagar, whom Porter claimed was mentally unsound. Porter had subsequently sold Hagar on, but took McClure to court. McClure called as a witness for Hagar's competence the wife of Greenwood, the man who had bought her from Porter. Since Greenwood had himself since sold Hagar on, Porter's counsel maintained that Mrs Greenwood was not competent as a witness, since she had an interest, through her husband, in Hagar's being determined sound. The court ruled that Mrs Greenwood's evidence was admissible.