*say sth in mitigation of sb's faults, crimes, etc, ie to make them seem less serious 为减轻某人的过失、罪行等说情.
law if you say something in mitigation, you try to make someone's crime or mistake seem less serious or show that they were not completely responsible
The captain added, in mitigation, that the engines may have been faulty.
formal a reduction in how unpleasant, harmful, or serious a situation is
His marriage had brought a slight mitigation of the monotony of his existence.