“It would probably be a total random. With a knife,’’ he uttered.

His doctor, a few feet away, scribbles in a notepad, documenting the evil cravings of a disturbed teenager and determining if there was any hint of intent.

“I could hide the body,’’ he goes on, speaking freely without his parents in the room.

He is alone with his psych. Just Jack Kelsall and the exposed depravity of his twisted mind.

This is the second time he had confessed the intrusive thoughts that had laid roots inside his troubled mind.

He wanted to kill. Just for the thrill of it.

The startling admissions proved horribly foretelling; dark premonitions that finally materialised into wickedness just 16 months later in a flat in Neutral Bay.

Jack Kelsall’s sick dreams had come true.

“He had been having intrusive thoughts about killing people on the way home at night,” Dr Susan Allman had recorded in typed notes after her appointment with the teen.

“He had taken a knife home with him one night but didn’t meet anyone.”

Kelsall had been treated for depression and was taking bi-polar medical Seroquel when he confessed to having such homicidal thoughts.

They “repetitive and persistent”, according to Dr Allman, urgings that he either could not exorcise, or even wanted to.

After moving to Sydney in 2010, Jack made only a handful of friends and spent his days working at Sydney Cooking School as a chef’s assistant, playing video games and reading fiction short story websites.

“He had no freinds, he was a complete loner,” his former boss George Deverell told The Daily Telegraph.

“He was obsessed with games, he basically lived for games. He would beg me to come in late because he would travel out to Penrith to go to a game expo.

“Jack was socially inept, he really didn’t have social skills. He was the most timid, quiet person you could ever meet. Very weird.”

In several online profiles, he adopted the unsuspecting name Lamant22 - a French translation of a popular 1984 novel called The Lover.

The book tells of an immoral sexual relationship between a 15-year-old French girl and an older Chinese man set in the 1920s. Lamant22 is also the handle of his Twitter account, which boasts of just one follower.

In one online profile, Kelsall, the adopted son of a NZ couple, wrote about his “mental problems, mainly Asperger’s.” and being diagnosed with “bi-poler depression (sic)”

On the dating website Mingle2, he went by the same French name, with a profile picture and the post: “Looking for man for intimate encounter.”

On the night of the murder on September 8, 2013, Jack sat and waited for his opportunity to stalk Morgan Huxley when he stumbled barefoot and blotto from the Oaks Hotel.

He stood in the open, not hiding behind the shadows, his eyes piercing through the darkness at his stumbling prey.

He even spoke to a security guard at the takeaway shop across the road as he took a sip of Powerade, showing little care for alibi.

With a bag slung over his shoulder, Kelsall starts jogging behind his victim as they cross Ben Boyde Rd into the dark. It was the last time Mr Huxley would be seen alive.

Two weeks after the murder, the net was beginning to descend on Kelsall, with police tipped off to his identity by the barrista he worked with George Lycarkis, who recognised him in the CCTV footage.

“The detective had his folder on the counter and I stopped making coffees and said ‘who’s that?’,” Mr Lycarkis said.

“He showed me the picture (of CCTV) and said ‘do you know this person?’ and I said ‘yes I do. That’s jack. He works here’.

“They were so surprised. They went from the café to his house basically that night.”

He was questioned by police and had several belongings seized from his home, including a computer.

The seizure of the latter was both grim and telling, bringing light the suspect’s sick fascination with death.

Forensic analysis of its hard drive revealed searches for ‘DNA’ and a catalogue of gruesome images of dead bodies and autopsies.

He also allegedly left a trail exposing his disturbing sexual fantasies, including animated child pornography.

Kelsall was arrested on October 9, 2013. Wearing jeans and a brown zip-up jumper, he was marched out of his family home in handcuffs, carrying a copy of the book Magician, a tome of an orphaned boy apprenticed to a master magician.

The DNA evidence was damning. The blood. The right ring fingerprint on Huxley’s door.

But equally damning was his constantly evolving story about what happened on the night of the murder.

Against an enormous weight of evidence, Kelsall pleaded not guilty.

In the closing days of the trial that had gripped Sydney, and once again exposed the frightening reality of randomness, Kelsall took a sip of water and walked calmly from the dock to the witness box to give evidence.

This was his defence, and this was his chance tell the jury “his side of the story” and to “make amends and tell the truth about the terrible lies that I’ve told.”

There was no admission of guilt, however. Not to critical evidence that appeared more categorical than most murder trials. But to those demons in his mind, the torment of his soul.

He confessed to only fantasising about a “thrill kill”, and that amid a consensual sexual act with the victim, someone else took over his gruesome narrative and did the deed he long dreamed of.

This was simply a game, Crown prosecutor Peter McGrath, SC told the court.

“Is giving evidence a game to you?” Mr McGrath asked Kellsall in cross-examination .

He liked playing games, both of a strategic nature and games of fantasy.

“Your father tells us you like chess, is that right?”

Kelsell: “Yes.”

“It’s a game of strategy?”

“To a point, yes.”

By Wednesday, it was check mate.