《后汉书·列传·张法滕冯度杨列传》
法雄每次巡行各部，登记囚徒，观察颜色，多能得到案情的真假，长吏不执行法令的都被解除印绶而离职。
雄每行部，录囚徒，察颜色，多得情伪，长吏不奉法者皆解印绶去。
Every time Fa Xiong went on an inspection tour, he would register the prisoners and observe their complexions, and was usually able to judge whether their confessions were true or false. Any high official who failed to carry out his orders would be stripped of his official seal and dismissed.