The following is from an appeal judgement:
The deceased's body was naked apart from her socks. Her trousers had been used to tie her hands behind her back. Her clothing had been extensively cut and torn with a sharp, bladed implement such as a knife. Professor Anthony Busuttil carried out the post mortem. He found that the deceased had suffered a prolonged assault with extensive blunt force injury and that a stout, sharp pointed bladed weapon had been used against her several times before and after death. A series of incised wounds across her neck had cut through the neck muscles, windpipe, jugular vein and carotid artery. The latter injury would have caused unconsciousness within seconds and death within two minutes. It was the cause of death. There had been between 12 and 20 cuts to the neck. Extensive injuries to the face, chin, neck and head were consistent with punches, kicks or blows with a blunt weapon. One was severe enough to produce a contusion on the brain. There were signs of mechanical asphyxia possibly involving the use of clothing as a ligature. There were penetrating injuries to the forehead and tonsils, the latter caused by the introduction of a sharp object into the mouth. There was a deep cut to the face. Cutting injuries around the eyes, and deep cuts to the breast, arm and abdomen, had been inflicted after death. Extensive bruising and cuts to the hands and arms indicated that the deceased had tried to defend herself. There were no signs of a sexual assault. Professor Busuttil said that he had been involved in many homicide cases and had not come across mutilation as extensive as this, or had done so only infrequently. Mutilation was quite uncommon, especially where there was no sexual element in the attack.
It sounds to me the perp was either mentally ill and/or off his head on some mood altering substance.
I would rule out a woman as I don't see many women having the physical strength to hold the victim down, who attempted to defend herself, and tie up the hands unless this was done after the victim ceased struggling.
The above doesn't sound like it came about over some teenage tiff about boyfriends, drugs or money owed. Even if J J stumbled on something its difficult to reconcile what brought about the extensive mutilation.