Dr. Christine Huxley is the true main villainess from Diagnosis Murder episode 4.14: "A History of Murder."
She was played by Lynnda Ferguson.
Christine Huxley is a surgeon and the daughter of surgeon Raymond Huxley, but as the episode progresses, it is shown that the father/daughter relationship is strained. However, when Christine learned that Raymond murdered Gregory Nordoff back in 1963 (learning this after Nordoff's remains were discovered early in the episode), she took villainous methods in order to protect her father. As part of her quest, the evil Christine killed Jane Ellington, using her scalpel to slit her throat. She also hid her father's old scrubs, which were covered in Nordoff's blood.
Christine, with Jane's blood on her own scrubs, was confronted by Mark Sloan over the revelation that her father killed Nordoff, due to the fact that Raymond's scrubs were bloody despite surgeries for that day being cancelled. Christine rushed to retrieve the old scrubs, but Mark got to them first and continued his confrontation. Christine confessed that she learned about the decades-old murder that morning, and that she was not surprised; believing that her father is capable of anything. Christine later showed her bloody scalpel to Mark, and stated that she killed Jane not for her inheritance, but to protect her father, and later on, she was arrested for Jane's murder.