'Crackers' was the word used by Torbjorn Kettlewell's barrister to describe the killer's personality.
Richard Wright QC was summarising the findings of two psychiatric doctors who both found Kettlewelll has an 'abnormality of mind'.
One of the doctors reported that during a consultation Kettlewell began beating himself about the head, causing bruising.
His mental abnormality was apparent at an early age, according to Kettlewell's brother, Michael, who gave evidence at the trial.
"He disgusts me," said the off-shore worker in a statement read to Teesside Crown Court.
"Not just because of what he did to Kelly, but because of the way he has always been.
"We have never got on as brothers should.
"He is manipulative, thinks highly of himself, and thinks he is always right."
Michael Kettlewell said his brother was obsessed with knives, and had stabbed him in the back with a butter knife when they were children.
"He is also obsessed with the Army," added Michael Kettlewell.
"He wears army clothes and tells people he served in the Army.
"I know for a fact he was never in the Army."
Kettlewell injured one of his three children when an air weapon he was cleaning discharged compressed air into the child's face.
This led to all three children being taken into care.
"Typically, he blamed Ms Franklin for that," said prosecutor Jami Hill QC.
"His manipulative nature was further illustrated by his sending Facebook messages to Ms Franklin pretending to be Julie Wass, while at the same time sending emails as himself.
"He was gauging Kelly's reaction to the messages, playing one off against the other.
"At every stage he was trying to exert control."
It was when Ms Franklin began resisting his controlling attempts that Kettlewell formed the intention to seriously injure, if not kill, her.
"He was clearly frustrated that he appeared to be losing the hold he formerly had on her," said Me Hill.
"This was the ultimate case of 'if I cannot have her, no one else will'."
The court heard another of Kettlewell's obsessions was computers.
He would spend hours playing games and even adopting the name - Torbjorn - of a video game character.
But for all his many personality flaws, the killing of Kelly Franklin was not foreseen.
"There may have been lots of showing off and bravado." said Mr Wright.
"But no one who has spoken in this trial thought Mr Kettlewell would harm anyone."