"He's minimised it, he's fabricated it and he's manipulated it to fix the case.
"And with so much of what he says, you're going to have to think very carefully about how much you accept.
"You may find what he told you in the witness box under oath very hard to accept."
Mr Mousley told the jury strangulation was a "vicious" form of causing death.
"It's not an instant way of causing death, and it can be very measured."
The jury had earlier been told Turner would have had 9.2 seconds to release his grip if he didn't want to cause serious injury to Emily.
Mr Mousley said: "What intention did Elliot Turner have in mind as he attacked her?
"What went on for those few but very significant seconds?
"When he finished, he left her motionless after the attack. If he had not intended to go as far as he did, he would've done something about it.
"He would have tried to save the girl he adored."
Mr Mousley said Turner did not have the courage to tell the truth about what happened on the night Emily died.
He said: "She did not deserve to die, it was not justified for Elliot to kill her.
"She did not die because Elliot defended himself against her, she did not die because he intended to cause only a low degree of harm.
"His intention was clear ... he's remorseless, he's controlling, he's possessive, he's vicious and he murdered her."
TURNER'S DEFENCE: 'SHE WAS ABLE TO FIGHT BACK'
Anthony Donne QC, defending Elliot Turner, said Emily had a strong character and was able to "hold her own" in their relationship.
He said: "She was well able to fight back verbally, at least if she thought she was on the receiving end.
"There was plenty of evidence that she was capable of striking and or striking back."
He told the jury Turner was "volatile and possessive" but was also "full of hot air."
He said: "Elliot Turner is brash, flash, boastful, spoilt, volatile, obsessive, possessive and obsessed.
"Frequently he very strongly expressed strong feelings of love for Emily Longley and strong feelings of hatred against her for cheating on him, or apparently cheating.
"It's a bit rich when he was cheating on her.
"Theirs was a world where sex was as casual as having a smoke.
"That doesn't mean that he couldn't be jealous and possessive.
"Jealousy, obsession, and possession can be the background to the murder but they do not prove it.
"They are part of a jigsaw puzzle."
Mr Donne said Turner was "all talk and no action" when referring to the threats he had made to Emily and others.
He said: "There is abundant evidence that Elliot Turner was known by those around him as an arch bulls***ter, a loud mouth, a hot air merchant - all talk and no action.
"No-one took anything he said seriously because of their long experience of his hot air."
Mr Donne also questioned the prosecution's allegation that Turner had used a sleeper hold to kill Emily.
He asked the jury to rule out that he had grasped his girlfriend hard around the front of her neck during an argument because there were no obvious injuries found.
He said the absence of injuries were "consistent with self defence and with a lack of intention to kill or cause serious harm."
FATHER'S DEFENCE: 'NEVER IN TROUBLE BEFORE'
Robert Grey, defending Leigh Turner, said he was a "law abiding citizen who had never been in trouble with the law before."
He asked the jury to consider the father's state of mind in the days after Emily's death.
He said: "Try and imagine the unimaginable where you are at work in your mundane life and suddenly there's a telephone call saying your son's girlfriend is dead at home.
"All sorts of things must go through your mind."
Mr Grey said his client's mind was in "turmoil" when he ripped up the letter from his son.
He added: "When people experience severe trauma such as this it doesn't suddenly end.
"It might last for days and weeks."
Elliot Turner denies murder but has pleaded guilty to perverting the course of justice.
His parents Anita, 51, and Leigh, 54, both deny perverting the course of justice by helping him cover up the alleged murder.
The trial continues.
- Solent News Agency
