Mary Hanlan was a serial killer and the mother of convicted rapist and murderer Vincent Hanlan whose trial Donald Mallard testified at. As a result of Ducky's testimony, Vincent was found guilty and sentenced to eight years in jail for the crime with his sentence wearing heavily on Mary who held a strong yet clearly insane belief that her son was completely innocent of the crime despite all the damning evidence that portrayed Vincent as the killer. This caused her to develop a bitter resentment and grudge against all local enforcement personnel and NCIS Agents.