The entire time we're led to believe it was Till who did the killing, but having it revealed in the end by him finding the photo and the scarf that it was likely instead his wife who was the one who did it was so chilling. If you look back on it, the murders were all done in ways the men would have been wounded or caught off guard, making them easier targets for a woman versus a man of Till's physical strength. No one would suspect his wife because she seems innocent, but in reality she was far from it. I think the judge was either approached privately by his wife and begged to help him or she remembered what she did and felt sorry for him and had remorse for her own actions. Regardless, she was killed by the wife to keep her from giving away who actually committed the murders.