Elliot Turner, 20, strangled Emily Longley in a jealous rage in the bedroom of the home he shared with his parents, Leigh, 54, and Anita, 51.
But when he wrote a note confessing to the crime, the couple, who ran a successful jewellery business in Bournemouth, destroyed the evidence and tried to help him cover his tracks.
Their deception was only discovered when police bugged their £350,000 home and overheard conversations in which they discussed the murder.
Yesterday following a four week trial, Turner, was found guilty of strangling his 17-year-old girlfriend, while his parents were convicted of perverting the course of justice. He had pleaded guilty to perverting the course of justice earlier in the trial.
Turner now faces life when he his sentenced later today (Tues) while his parents have been bailed to a later date, but have been warned they too face jail.
Dubbed 'All Talk Turner' by his associates because of his boasting, Turner was well known around the bars and clubs of Bournemouth and Poole where he headed up a gang of wealthy young men known locally as The Firm.
Funding his lifestyle through handouts from his parents, the 20-year-old bodybuilder met Miss Longley just four months before he killed her.
The court heard how he displayed signs of extreme jealousy and obsession and eventually began making daily threats to kill against Miss Longley.
In early 2011, the part-time model returned to her native New Zealand to see her parents, but Turner had monitored her activities on Facebook and had become incensed when he thought she was seeing other men.
When she returned, Turner's obsession only increased and the court heard how in the days before her death he had turned up to a club in Bournemouth, armed with a lump hammer and threatening to kill her.
On the night she died the pair had a violent argument in a café, before she agreed to go back to his home in the affluent Queen's Park area of Bournemouth.
Turner claimed in court that he had grabbed Miss Longley around the neck when she physically attacked him, but insisted he had not intended to kill her.
He told the jury when he stormed out of the bedroom he had believed she was sleeping and only discovered her lifeless body the following morning when he went in to wake her.
When arrested at the scene he had his passport in his pocket and his bags packed, the court heard.
However a lack of conclusive evidence led the police to bug the family home and Mr Turner was heard admitting using bleach to destroy a confessional note his son had penned.
During another discussion Mrs Turner is heard refusing to accept that her son had done anything wrong, leading her husband to comment: "He (Elliot) f****** strangled her."
