Warning: Contains graphic evidence that some people may find upsetting.
The star witness in a Dunedin murder trial had told police he's a compulsive liar.
Venod Skantha's trial continues in the High Court - where he's pleaded not guilty to murdering 16-year-old Amber-Rose Rush.
He also pleaded not guilty to four counts of threatening to kill at the outset of his trial before the High Court.
A teenage former-friend of Skantha is currently on the witness stand - hidden behind a screen.
The jury watched footage of his initial interviews with police.
He said Skantha made him drive them to Rush's house the night she was killed - and later admitted the crime.
But when questioned about inconsistencies in his story, the teen told police he has an issue with telling the truth.
"I'm a compulsive liar pretty much... But this is definitely the truth."
'Vinny what have you done?': Teen says doctor admitted killing Amber-Rose
The teenager told police he feared for his own life after Skantha admitted he had murdered a teenager and stolen her cellphone.
The teen today told the murder trial the accused returned from the teen victim's house holding her blood-covered cellphone.
The teen witness told police in a video interview played to the court today that the accused later told him he had killed the victim, slitting her vocal cords to stop her screaming.
The trial for Skantha, 32, entered its second week today.
The victim was fatally stabbed in the bed of her Corstorphine home around midnight on February 2 after the defendant was driven to the address by a teenage boy.
The boy, who has name suppression, said he drove the doctor to Amber-Rose's house the night she was killed.
The teen's police interview is being played to the court today.
He said Amber-Rose and Skantha had an argument via Facebook messenger the night she was killed.
"I sent him a photo of an Instagram post Amber had put up. Venod got a bit ticked off. He said 'I'm coming to get you'."
He said he once held a party at Skantha's house - when the doctor got into an altercation with six other people.
The youth said Skantha took a few kicks before getting hold of a samurai sword - which quickly broke up the fight.
"He didn't seem fazed at all afterwards."
Accused said he had 'master plan': Teen witness
When Skantha arrived he told him to get in the car - and that the teen would be driving.
"Drive to Amber's house. I've got a master plan," the teen said Skantha told him.
"I thought he'd had too many wines. He does like his liquor."
The boy says Skantha told him to park around the corner, where he waited and listened to music.
"He was away for five to 10 minutes. Then he comes back and says "open the door. Don't let me touch it'."
The teen said Skantha was holding Amber-Rose's phone.
"It was in a clear case with her licence in it. I saw it was covered in blood. Then I saw him put one of his kitchen knives in the [car's] side pocket.
"I used to cook for him quite a lot – I knew those knives," the teen said.
'Vinny, What have you done?'
"I asked him; Vinny, What have you done?" He said it doesn't matter."
The young witness says Skantha later admitted to him he'd killed Amber-Rose.
"I didn't know what I was feeling."
He said Skantha asked him to drive to nearby Blackhead Quarry - where he disposed of her phone.
"Then we lined the boot with cardboard boxes. He put bags of his clothes in the boot, and shoes.
"Later he asked me to clean the shoes - but I left blood spots on them on purpose."
The shoes were later found by police - hidden in Skantha's Balclutha girlfriend's garage.
The teen says he drove Skantha to Balclutha, and back to Dunedin the following day.
He also accompanied him to meet with Lisa Ann Mills - Amber-Rose's mother.
"I just sat there thinking, 'I'm in the room with her murderer. What the f*ck am I doing?'"
Vocal cords 'severed' to prevent screaming
Skantha and his girlfriend dropped the youth off at his Dunedin home.
On the drive back to Dunedin, he and Skantha talked about what had happened.
"[I asked him] what he was going to do with the knife. He said – 'I'll cut some chicken or something'."
"Vinny told me he cut her ear so it was dangling off. She was just about to scream - and he says he cut her vocal cords. There was a dog in there but it was bloody useless.
"Then he just walked off – left the key in the door."
When the detective left the room in his initial police interview - the teen turned to the camera.
"Whoever does see this recording – I'm deeply sorry for what's happened, I wish I could've done something."
The teen said he himself felt unsafe after Skantha allegedly admitted the murder to him.
"I just had to act like the old me. It was just the whole, 'I don't care,' 'you're ruthless'."
"I didn't want to say it, but to keep myself alive I had to… To keep him happy, and to keep myself from the city morgue."
At one point - he fearfully asked police whether Skantha would see the recording of the interview.
"I don't like to upset Vinny, because he can get quite aggressive."
• Dunedin doctor murder trial: Accused Venod Skantha killed teen Amber-Rose Rush to protect his career: Crown
• Dunedin doctor murder trial: Accused discussed potential suspects with victim's mum: witness
• Dunedin doctor Venod Skantha on trial for murder of Dunedin teen Amber-Rose Rush
• Amber-Rose Rush's death a 'suicide': Murder accused to victim's mum