A teenage vampire fanatic accused of killing a pensioner and drinking her blood was arrested two months earlier when he asked a policeman to bite his neck, a court has heard.

The art student, 17, who cannot be named for legal reasons, denies stabbing Mabel Leyshon, 90, with a knife 22 times and removing her heart in a "macabre" killing at her Llanfairpwll, Anglesey, bungalow on 24 November.

But Sergeant Peter Nicholson said he made no connection between the case and his arrest on 23 September, when the boy told him: "Bite my neck."

I attempted to speak to him and try to get him to leave. He didn't make any sort of coherent response - all he could say was 'bite my neck'

Roger Thomas QC, prosecuting

The boy was arrested for earlier begging a local student to bite him, helping his quest to transform into a vampire.

Tuesday, Mold Crown Court heard pensioner Mrs Leyshon died from multiple stabbed wounds and her chest had been "ripped open".

Pokers were found at her feet in the shape of a cross, the jury was told.

Her heart had been removed, wrapped in newspaper and placed in a saucepan on of a silver platter next to her body after blood had been drunk from it in a "macabre ritual", it was said.

'Bite my neck'

Prosecuting, Roger Thomas QC, said DNA found in the blood at the scene matched that of the defendant.

He claimed the student was "obsessed" by vampires, with vampire books and magazines found at his home and traces of vampire websites identified on his home computer.

Wednesday, sitting instead at Chester, jurors heard from the police officer who arrested the teenager in September, two months before the murder.

The student had visited the lodgings of a German exchange student, 16 - met through a Chinese friend, 18 - who shared the accommodation.

He chatted with the girl for two hours before accusing her of being a vampire and begging her to transform him by biting his neck, it was claimed.

When she refused, he allegedly became violent and had to be dragged away by his friend and the lodgings' landlady, who called police after he punched himself on the nose and asked the pair to smell his blood. Llangefni-based Sgt Nicholson turned up at 0130 GMT.

Unlinked incidents

He told court: "I attempted to speak to him to try to get him to leave peacefully. He didn't make any sort of coherent response. All he could say was 'bite my neck'."

The defendant was handcuffed, arrested for breach of the peace and taken to the police station, but never charged.

Sgt Nicholson said he failed to link that incident with Mrs Leyshon's horrific murder, which made national headlines when police revealed a ritualistic motive was suspected.

He said he still did not connect the incidents when North Wales Police made a desperate plea on the BBC's Crimewatch programme in December.

"I didn't actually see the Crimewatch programme because I was working at the time. But no, I did not contact the programme."

'Body draining

But constable Alison Hughes - who was first at the grisly bungalow scene - told court she was unable to say whether the murder was common knowledge on Anglesey because seniors told her not to tell police colleagues about the incident.

Also on Wednesday, Home Office pathologist Dr Brian Rodgers - who conducted the post-mortem examination - said he thought 4ft 11ins Mrs Leyshon was stabbed 22 times from behind as she sat and watched television.

He said: "At the time I thought this was an attempt to dismember Mrs Leyshon's body.

"But, when I looked more closely, I thought the wounds were in a place you would expect if you were trying to drain a body."

The defendant denies ever being in Mrs Leyshon's home and the trial continues at Mold Crown Court, expected to last about two weeks.