She knew, what he had suffered under the hands of his father, Abraxas Malfoy, when he graduated. Lucius didn’t want to join the death eaters like his father, but his father used some compulsions and loyalty potions, and even the imperio was used, in order to get his son’s loyalty to the Dark Lord. After the war, every death eater was captured, including Lucius himself. Lucius was prosecuted for his actions. He was questioned under veritesarem and Lucius revealed the fact that he was put under compulsion and loyalty potions by his father after the veritesarem was able to hold back the potions and compulsion in his system and that the Dark Lord reapplied the imperio on him every Sunday evening. When they tested him with the help of an inheritance test, everything matched, what he had said. Lucius was sent to the purging chamber of the goblins, where every potion was expelled out of him and the imperio was broken. The goblins managed to remove his dark mark and Lucius was a free man.