The judge in the trial of a man accused of murdering New Zealand teenager Emily Longley told the jury "a cool head is called for'' in deciding the fate of the wealthy 20-year-old.
Emily, 17, was found dead in Elliot Turner's bed at his family home in Dorset in May last year.
Turner, 20, has denied murdering his girlfriend by strangling her in a jealous rage, saying he defended himself during a fight.
His parents, Anita and Leigh Turner, have denied charges of perverting the course of justice - a charge Turner initially also pleaded not guilty to, but admitted earlier this week.
Justice Dobbs began her closing speech to the jury of 11 men and one woman overnight at Winchester Crown Court.
She told the jury to put aside any prejudice or sympathy and said "a cool head is called for'', the Bournemouth Echo reported.
She also directed them on the points of law, and reminded them of the evidence they have heard over the past 18 days.
Fern Russell, representing Turner's mother Anita also gave the jury her closing speech.
It is alleged Anita Turner perverted the course of justice by removing from the house a jacket worn by her son on the night of the alleged murder.
But Miss Russell said the prosecution had made no effort to explain how the jacket could have been of use to the police.
"All the available evidence is the removal of the jacket alone had no tendency to pervert the course of justice.''
Yesterday, in summing up the prosecution's case, Timothy Mousley QC said Emily probably stood no chance against Turner.
"We submit he's remorseless, he's controlling, he's possessive and he's vicious and he murdered her,'' he said.
Turner manipulated his parents and told his mother to change her story, the court was told.
"It is clear Elliot pulled the strings.''
In summing up the defence case, Anthony Donne QC said Turner was "brash, flash, boastful, volatile, obsessive, possessive and obsessed'' but that did not prove he was a murderer, and he acted in self defence.
Turner was arrested after Emily's death on May 7 last year but released on bail.
Emily was born in Britain but her family moved to New Zealand when she was nine and she was raised in Auckland, where she attended Hauraki School, Westlake Girls High and Takapuna Grammar.
She had returned to study in Britain and lived with her grandparents in Bournemouth while continuing her studies there.
