Venod Skantha (32) is on trial before the High Court at Dunedin accused of stabbing 16-year-old Amber-Rose Rush to death in her Corstorphine bedroom on February 2 last year.
The prosecution case is that the victim had threatened to go to the police and the defendant's Dunedin Hospital bosses with allegations of sexual molestation and posted portions of their conversation online.
The Crown's key witness, who said he drove Skantha to and from the Clermiston Ave address and saw the defendant with a bloody knife and the victim's possessions, spent nearly three full days in the witness box.
After more than a day of cross-examination, defence counsel Jonathan Eaton QC concluded his questioning by quizzing the teenager about an interview with police he had undertaken two months before Amber-Rose's death.
He confirmed it had been about sexual allegations from a 15-year-old girl against him and a 38-year-old man.
The teenager conceded he had initially lied to the police about his involvement but later admitted to the crime.
''The reason I didn't want to say anything was because I didn't want to, you know, say it in front of my mother [who sat through the interview]. I didn't know how my mother would feel about it,'' he said.
Mr Eaton suggested it was indicative of someone who was comfortable lying to police.
''You've lied to the police about what happened to Amber,'' Mr Eaton said.
''No'', the witness replied.
''You do know what a compulsive liar is ... That's you isn't it?''
''No,'' the witness replied.
''You've lied to the police and you've lied to this jury and you've done so to falsely implicate Dr Skantha?''
''No.''
After the teen's evidence had finished, Justice Gerald Nation told the jury it would be wrong for them to reason that because he had lied in another case he must have killed Amber-Rose.
The reason he had allowed the line of questioning was because it was relevant to the witness's veracity, the judge said.
''Ultimately, it will be entirely for you what significance, if any, you place on the fact [the witness] did tell lies to police when he was first interviewed about the events of December 4, 2017, and to what extent that might affect your assessment of his credibility as a witness,'' the judge said.
Earlier, Mr Eaton squarely put it to the teenager that he had been the one who stabbed Amber-Rose to death.
The teenager said he called a friend at 11.54pm, while Skantha was allegedly in the house committing the murder, because he was bored.
But the defence suggested he had done so to create an alibi.
The witness denied that was his intention.
''Did you go and challenge Amber about what she was posting [on social media] about Vinny?'' Mr Eaton asked.
''No,'' the teen said.
''Did you get upset and do something stupid that you regret?'' Mr Eaton asked.
''No.''
After the alleged murder, Skantha and the teenager went to Balclutha where they spent two nights at the defendant's ex-partner's home.
While there, he said the defendant acted out the brutal stabbing.
''He grabbed a knife and demonstrated what he did to her on me,'' the witness said
''This is one thing I'll never forget that'll linger with me for the rest of my life.''
He also said Skantha instructed him to clean a pair of grey suede shoes which he allegedly wore to commit the murder.
The teenager said he had deliberately neglected a spot of blood on the defendant's shoe and left them in a garage so officers had evidence to link the defendant to the crime.
His vagueness and inconsistencies concerning details of the cleaning led Mr Eaton to suggest he had planted the evidence to frame Skantha as the killer.
The witness denied that, as well as further similar assertions.
Mr Eaton submitted he had planted blood in Skantha's silver BMW as well.
''You must've had, whether on Amber's licence or something else, some of her blood. You had access to that and rubbed or flicked it around the car,'' he said.
The trial, before a jury of 10 men and two women, is expected to hear forensic evidence today.
