In Stratienko v. Cordis Corp., the Sixth Circuit considered the plaintiff's argument that summary judgment was not proper where the evidence on which the District Court relied came from persons with an interest in the outcome of the case.
The plaintiff cited this language from the Supreme Court's decision in Reeves: "[T]he court should give credence to the evidence favoring the nonmovant as well as that ‘evidence supporting the moving party that is uncontradicted and unimpeached, at least to the extent that that evidence comes from disinterested witnesses."
The Sixth Circuit explained that this does not mean that the undisputed evidence from interested witnesses cannot be used in support of summary judgment, concluding that the issue "is not whether the district court could consider the affidavits of Cordis but instead whether the affidavits were uncontradicted."
This case gives me cause to recollect a passage from the little book I have on English legal history, which says in part: "The parties themselves, and interested persons, were excluded from the witness box at common law on the assumption that their testimony would be biased and therefore worthless." Baker, An Introduction to English Legal History 288-89 (Butterworths 2d ed. 1979).