A ruthless teenage thug high on nitrous oxide murdered a man with a machete in cold blood, a jury has decided.

Saymore Kwashira suffered catastrophic internal bleeding after Romaine James thrust the lengthy weapon into his stomach.

James maintains he was acting in self defence, but following a nine-day trial at Leeds Crown Court, the jury unanimously found him guilty of murder.

The 18-year-old had been taking the nitrous oxide, also known as laughing gas - at at an address of Winrose Avenue, Belle Isle, in the early hours of November 11 last year.

Mr Kwashira - often known as “S” - was friends with the homeowner’s daughter and often stayed at the property. He was also present.

James and others had gone to the property that night, claiming they were there to “chill” - to relax.

CCTV showed James outside the property before the killing with a balloon in his mouth which was filled with the nitrous oxide.

The emergency services were called to the property at 12.17am. James had fled and was again caught on CCTV, this time holding a machete as he left.

The weapon was never found, along with the clothes he was wearing.

A witness gave evidence that James said to the victim prior to the killing: “What are you chatting sh** about me for?”

A pathologist’s report later concluded Mr Kwashira was stabbed twice - once in the stomach, and once to the neck.

The neck wound had severed part of his ear and part of the base of the skull.

The stab wound to the abdomen ruptured two major blood vessels, proving fatal. Almost two litres of blood had collected in his abdominal cavity.

James, of Reginald Mount, Potternewton, handed himself into the police station 19 days after the killing.

He was accompanied by his mother and gave a mainly no-comment interview.

James claimed during the trial that Mr Kwashira was holding a machete and had attempted to rob him.

He claimed he became scared that Mr Kwashira was being serious, so tried to leave the room.

Saying he was prevented from doing so, he grabbed the machete and swung at Mr Kwashira, causing the fatal injury.

The jury did not believe his story and returned their guilty verdict after just over five hours of deliberation.

James will be returned to court on November 5 to be sentenced but will be handed a life sentence.

The judge will decide the minimum period he must spend locked up.

Ruthless machete teenager guilty of murdering man during gathering at Leeds flat