His parents, Leigh and Anita Turner, also face jail after they were found guilty of perverting the course of justice.
The defence lawyer at the trial described ex-public schoolboy Turner as “brash, flash, boastful, spoilt, volatile, obsessive, possessive and obsessed”.
The grandson of a millionaire silversmith, Turner was out partying around the posh bars of Sandbanks in Dorset just days after he strangled Longley to death.
Longley was born in London but emigrated to New Zealand aged nine. She moved back to Britain in 2010 to live with her grandparents.
Turner faces life in prison when he is sentenced today.
His father, Leigh Turner, destroyed a letter his son had written that confessed the crime to his mother.
The jury heard that Elliot had “pulled the strings” in the family home in the aftermath of the killing, and that his parents had helped cover his tracks.
Police covertly recorded the Turner family home during the murder investigation, catching Leigh Turner telling his wife: “We’ve perverted the course of justice, we’ve destroyed the vital evidence in this case.”
Anita Turner is heard to reply: “Yes because he is our son, we’ve done the right thing.”
Turner senior is later recorded saying: “Stop denying it. He ****ing strangled her.”
After hearing the guilty verdict, Longley’s father Mark said: “What we have heard over these five weeks has shocked us and disgusted us.
“That a man so evil like Turner could treat a gentle, loving girl like Emily in that way, that he could treat her so violently, is beyond belief.”
The court heard that Elliot Turner had threatened Longley on multiple occasions before killing her, and even asked a friend to attack her with a metal lump hammer.