Lord Mansfield's Rule Law and Legal Definition
Lord Mansfield's rule refers to a rule of evidence which provides that both husband and wife are not entitled to give testimony on the question whether they had access to the other at the time of conception.
In Serafin v. Serafin, 67 Mich. App. 517 (Mich. Ct. App. 1976), the court held “ in a suit for divorce by a plaintiff husband who denied paternity of a child, the application of Lord Mansfield's rule, which provides that neither husband nor wife will be permitted to bastardize the issue of the wife after marriage by testifying to the non access of the husband, unconstitutionally takes property from the plaintiff without due process of law where application of the rule prevents plaintiff from introducing his own evidence and makes the presumption of legitimacy an irrebuttable presumption.”