Deuteronomy 22:15

then shall the father of the damsel, the designation leaving the matter of a probable guilt open, and her mother, the parents being very decidedly concerned in this accusation, take and bring forth the tokens of the damsel's virginity, as it was supposed distinguishable by spots of blood, unto the elders of the-city in the gate, for it was the custom to save this evidence for just such an event;