Covert police surveillance recorded Elliot Turner saying "I just f****** grabbed her as hard as I could" in the days after he allegedly murdered his girlfriend Emily Longley, a UK court has heard.
Winchester Crown Court has heard police surveillance recordings taken from Turner's parents' home in Bournemouth, South England, where 17-year-old Kiwi teenager Longley's lifeless body was found on the morning of May 7 last year.
In the recordings, 20-year-old Turner can be heard saying "she kept punching and kicking me" before saying "I just f****** grabbed her as hard as I could" the Bournemouth Echo reported.
He also said, "I went nuts, I flipped" before he tells of fetching Emily a glass of water because she was in pain.
The recordings also reveal conversations between Turner's parents - Leigh and Anita Turner - who are charged with perverting the course of justice.
Leigh, 54, speaks of destroying a confession note left by his son in bleach and that he feels a "terrible burden".
He also says Elliot "f****** strangled her".
The jury, made up on 11 men and one woman, also heard police interviews with Anita Turner, 51.
In the interview, Anita tells police she saw Longley in the kitchen around 5am, "getting a drink of water or something".
The Turners deny all charges.
The jury also heard further details about the sleeper hold - a popular wrestling move where the victim's face is pressed against the inner elbow of the attacker.
Medical experts say this could have possibly been used to strangle Longley or render her unconscious.
Forensic expert Dr John Payne-James, who was first asked to demonstrate the move, told the jury it was possible to apply the hold that renders someone unconscious within seconds and leaves no marks.
This method of strangulation pinches nerves in the neck which interfere with the victim's heart beat but does not necessarily produce any visible signs of internal or external injuries.
Payne-James said a recent study of trained officers putting holds on 24 consenting people had an average unconscious time of 9 seconds.
In cross-examination, he accepted that depending on the exact hold Longley could have had one or both arms free to fight her attacker.
Longley's post mortem examination found petechiae haemorrhages on her lips and eyes, commonly caused by rising pressure in the chest or compression of the neck.
The trial continues.