Benson Walton's POV:
Kevin had 'examined' Julie's body, and what he had examined was Julie's remaining soul. Even her soul was incomplete, which made her unable to find the way to the Moon Palace's courtyard. Even the messenger who guided the soul seemed to have forgotten her. She could only wander around the grave like a homeless ghost.
Kevin realized that some kind of power had long corroded her soul. Furthermore, unlike the normal state of the soul, which could repair itself, there was no trace of repair. He found a strange power in Julie's soul, which was exactly what we found today.
With all the factors mixed, a conclusion was already obvious.
More than twenty years ago, perhaps before Layla's death, the murderer used a strange power to control Julie, the servant of the manor. This caused Julie's soul to be damaged, and she became a lunatic.
Who would be so free as to lay their hands on an ordinary servant?