A violent and jealous boyfriend, fearful his aspiring model girlfriend was being unfaithful to him, strangled her in bed and then received help from his parents to cover up the murder, a court heard today.

Elliot Turner, 20, ''went absolutely nuts'' and strangled 17-year-old Brockenhurst student Emily Longley in a culmination of a month of anger and upset over his suspicions she was ''twisting his heart'', Winchester Crown Court was told.

His mother, Anita, 51, and father, Leigh, 57, initially told police they had heard Emily talking in their son's bedroom, even though the prosecution say she was already dead.

Turner said they had argued the night before and she had attacked him, and that when he woke up beside her she was dead.

When arrested he had his passport in his pocket and his bags packed, the court heard.

Leigh and Anita Turner allegedly removed their son's jacket from the bedroom when the police were distracted by Leigh Turner dropping his tablets on the floor, with Anita Turner taking it.

Police bugged their house in Bournemouth, in the weeks after the alleged murder and heard the pair say they had destroyed a letter that Turner had written.

In evidence read out to the court, Leigh Turner was alleged to have said that Elliot strangled Emily.

The court also heard that Turner stated: ''I cannot tell them (the police) about the letter I destroyed by bleach saying he (Elliot Turner) killed her but he didn't mean it.''

Earlier he had said: ''We have perverted the course of justice by destroying evidence.''

But Anita Turner was heard to say they had been right to do it.

Elliot Turner was heard to say: ''I just flipped. I went absolutely nuts... I just lost it. I grabbed her as hard as I could. I pushed her like that.''

Elliot Turner denies murder and perverting the course of justice, while Anita and Leigh Turner, who run a jewellers in the resort, both deny perverting the course of justice.

Tim Mousley QC, prosecuting, told the jury that Turner and Emily had a short volatile relationship which had included Turner being violent towards her in front of friends, and on several occasions saying he would kill her.

''However short their relationship was, during it Elliot Turner showed himself to be threatening, aggressive, violent, controlling and possessive towards Emily Longley.

''These aspects of Elliot Turner became more and more obsessive and culminated in killing Emily Longley in his bedroom in the middle of the night,'' the barrister said.

He alleged that Turner strangled her and that there were tell-tale haemorrhages under her eyelids, consistent with neck compression.

He had suspected a month before the alleged murder in May last year that Emily had been unfaithful when she had returned to Auckland in New Zealand to visit her parents.

The student had been born in Britain but her family had emigrated when she was nine. She had returned to live with her grandparents in Bournemouth, to study.

Turner had then become angry over a Facebook picture of her ''flirting with lads in a car'' in New Zealand.

He hated the way she wore revealing clothes and called her a whore on the night the prosecution say he strangled her, the jury of one woman and 11 men were told.

Turner made previous threats to kill Emily using a lump hammer and even practised how to strangle her with his friend Tom Crowe, the court heard.

The pair argued and then made up several times in April and May with one minute Turner buying her flowers and a Twix but then Emily texting him to say: ''Hit me with a mallet? Do what ever you want to me - I will never get back with you. I actually hate you.''

The barrister explained that Turner was suspicious Emily had been seeing three men in the Bournemouth area in addition to his fears she had been unfaithful while in New Zealand.

Turner's fears were written down by Emily after they went away to the Isle of Man.

In a note on hotel paper Emily wrote: ''I love you. Don't say you will kill me. Stop talking about your ex-girlfriend and stop being so constantly aggressive. Be more cool because that's so much more hot.''

On one occasion in the weeks before Emily died Turner had told friends he had killed her using the hammer in a nightclub car park but then said he was joking.

Mr Mousley said that his fears and anger led to the alleged murder in the early hours of May 7, after Emily agreed to stay at his home despite a series of rows and violence, but the ambulance was not called until 9.45 that morning after several phone calls between parents and son.

When Turner was arrested he said: ''I never meant to harm her, I just defended myself.'' He then made no comment in police interviews.

Police examined his computer and found searches about death by strangulation, the court heard.

The jury was told Leigh Turner admitted destroying the letter and distracting police so the jacket could be removed. He said he had returned home from the jewellery shop to find Elliot Turner with his bags packed.

Anita Turner admitted taking the jacket but could not account for the delay in calling for an ambulance, the court heard.

The trial is expected to last four weeks.