A man has been found guilty of strangling a boy to death after the jury heard details of disturbing calls he made hours before the murder.

Chadley Sheridan faced a NSW Supreme Court jury over the murder of a 16-year-old boy who died in a Charlestown unit near Newcastle in March last year.

The autistic boy was found dead by his father, who had welcomed Mr Sheridan into the home.

The 25-year-old had admitted to strangling the teenager but pleaded not guilty, with his defence team arguing he was mentally impaired due to psychosis.

Throughout the trial, the crown and defence were not in dispute over Sheridan’s involvement in the boy’s death, and instead argued the extent to which his use of the drug ice contributed to his mental state.

But the jury on Thursday agreed with the prosecution’s case and found his psychosis was due to the temporary effects of taking ice.

Sheridan was convicted of the murder.

The jury was told that in the day of the murder, the 25-year-old spoke to his sister on the phone and she described him as sounding scared and “like a little child”.

She reported not being able to understand what he was saying and that he “just kind of spoke a few words”.

“He couldn’t really get the words out that she was trying to say,” she said.

The jury also heard Sheridan experienced signs of psychosis in the years before the incident, including the “bizarre belief” he was being followed by the Chinese government.

The 25-year-old’s first officially recorded psychotic symptoms were in 2018 when he was noted as expressing “bizarre beliefs”, the court was told.

“The bizarre beliefs were that the Chinese government was somehow interested in him and following him,” court documents stated.

“And that he had some supernatural connection to God.”

Forensic psychologist Olav Nielssen gave evidence during the trial that Sheridan had an “underlying psychotic illness which was exacerbated by drug use” on the night of the alleged murder.

In the days leading up to the incident, Sheridan had both smoked and injected ice and was acting out of character, the court was told.

Sheridan’s brother, who had picked him up on the night before the incident, described him as “completely off”.

“Like, he was distraught – completely not present, damaged, in a really bad headspace,” the brother said.

Sheridan had been welcomed into the unit on the night of the murder and remained there alone, with the sleeping teen in the other room, when his father and another person went out for around an hour.

The court heard Sheridan was drinking Woodstock and cola cans and playing PlayStation in the living room at the time they left around 10pm.

Later, the father said he received a call from Sheridan where he sounded “upset”.

During his evidence in the trial, the father told the court he could hear Sheridan was “upset and stressed” when he arrived back to the unit.

“I said what’s up mate, you alright,” the father told the jury.

He returned to the unit and sat with Sheridan and the other friend in the lounge room for around 45 minutes, after which he went into his son’s bedroom to turn off a fan.

Upon finding the boy on the floor with blood coming out of his mouth, the father called for the friend to call triple-zero and commenced CPR.

Paramedics were unable to revive the boy.

CCTV footage from a neighbouring property showed Sheridan leaving the unit in a car at 12.38am. He was tracked down and arrested by police in a KFC carpark roughly an hour later.

Sheridan was taken to the Calvary Mater Hospital for treatment and was later charged with murder.

He will face court for sentence at a later date.