IMHO this man has demonstrated himself to be a violent, sexually deviant murderer - a dangerous human being.
Evidence indicates that he was planning/looking for an opportunity to enact his murderous, deviant sexual desires on a selected victim e.g. being on school grounds when he should not have been there, accessing the school alarm system, accessing violent 'bride' rape, murder and necrophilia videos on the internet; collecting items to build a 'rape kit'; establishing the Easter plans of selected staff; loitering around the girls' toilet block, etc.
It was just a matter of time.
His affect seems unusual: the smirking/smiling facial expression could be misinterpreted as friendly by unsuspecting others. However, it masks a dark, deviant internal world. This can be seen when detectives interviewed him and he described his desire 'to kill' with details of how he bashed, raped and murdered his victim all the while smirking/smiling. He's not mirroring at all. He's smiling as he links into his own depraved internal world.
We look to Psychiatry to find explanations for this deviance, this human pathology - so devastating to other well-functioning people, law abiding citizens going about their normal daily living, working, building a life, a family, a future. Psychiatry is still evolving and struggles. It can cover the broad spectrum as it deals with the specific details of this murderous crime i.e. working backwards, what traits have been in evidence in the conduct of this particular crime, etc. However, it will take a more detailed examination of the life of this man, his environment, his significant others, his influences, his unique response to those influences, early evidence of a pathological response(s), how it was/wasn't it handled, what adjustment/maladjustment occurred, etc.
Looking at this man, he has a rather large head, with low-set ears, a low brow line and a protruding jaw. Allegedly, people in the Netherlands described him as 'King Kong' due to his unusual strength and unusually hairy body. In addition to the observed and self-described emotional deviance, possible biological/neurological factors would need to be examined and taken into account in any diagnosis IMO. So this biological/environmental element needs further work.
Is such a man capable of 'morality' as his lawyer put before the court? Was moral and virtuous conduct witnessed in his crime? Was he showing a moral side when he confessed to Stephanie's murder? Or was he caught by Police with indisputable evidence of his guilt. Was he excited by the re-telling of the details of his crime to detectives? Did he show remorse of any kind during his interviews? We know he had enough intelligence to go to some lengths to scatter the evidence, to mislead detectives about the rings involving his twin brother and to go to some lengths to conceal his own crime, but where was the alleged moral element? Where was the remorse?
The concept of morality as suggested by the Defense? Clutching at straws IMO. Morality is a higher order characteristic inconsistent with a dark drive 'to kill', the enjoyment of murder, violent rape, necrophilia and vile destruction of a human body using fire to obliterate evidence of bodily injuries. We can speculate that a significant part of their internal world is dead, damaged, so other people are mere objects to them. They don't value higher order concepts such as self or morals. They are driven by more primitive drives from their damaged, internal world. This man has allegedly had pathological thoughts since middle childhood (aged 7 years) as reported in msm. His pathology is entrenched given all those years of deviance, and now he has acted out that internal pathology as an adult aged 25 years. He has demonstrated that he is a danger to society.
How much mad? How much bad? Big questions for psychiatry and the Court to struggle with. Where to incarcerate a man who has admitted he has a desire 'to kill others'?
He will still have this desire which may not be gender specific. It may become stronger now that he has 'killed' i.e. such a violent bashing, rape, murder and vile burning of the corpse. He collected trophies i.e. photographs and the bra, a feature in common in other serial killers. His is a criminal deviance makes him a danger to others.
Some thoughts for today. My opinion only.