Baron and Feme, in English law, is a phrase used for husband and wife, in relation to each other, who are accounted as one person. Hence, by the old law of evidence, the one party was excluded from giving evidence for or against the other in civil questions, and a relic of this is still preserved in the criminal law.
Baron and Feme, in heraldry, is a term used when the coats-of-arms of a man and his wife are borne per pale in the same escutcheon, the man's being always on the dexter (right) side, and the woman's (or, more precisely, the woman's father's) on the sinister (left). This is the normal way of displaying a married couple's arms together; only when the woman is a heraldic heiress is it not used (in such a case her arms are displayed on her husband's on an inescutcheon of pretence).