The stepbrother of British teenager Becky Watts has admitted killing her but denied murder in a crime the prosecution claim had a sexual motive.
Nathan Matthews (28) pleaded not guilty to murder at Bristol Crown Court, but a jury has been told he admits killing the teenager - saying he tried to kidnap and imprison her before strangling her.
Matthews' girlfriend Shauna Hoare (22) has denied all of the charges against her, including murder.
He claims to have acted alone and has denied conspiring to kidnap her.
The prosecution told the court Becky died as a result of a plan by Matthews and his girlfriend Shauna Hoare to kidnap her, motivated by their "apparent dislike of Rebecca Watts" and a sexual interest in "attractive teenage females".
Becky (16) went missing from her home in St George, Bristol on February 19th. Her body parts were discovered at a property in the city on March 2nd.
Opening the case, prosecutor William Mousley QC said that Becky was killed in her bedroom on February 19th, adding: "She was suffocated, despite her fighting for her life. There followed a deliberate, carefully planned and grotesquely executed plan to cover up her killing".
The prosecution claims that after her death, Becky's body was cut up with a knife and power saw, with the parts then being packed and moved to prevent them being found.
Mr Mousley went on: "The police investigation led to the discovery of evidence which suggested that there was a sexual motive behind the intended kidnap/imprisonment.
"Evidence was found on telephones, computers and computer-related equipment connected to both Nathan Matthews and Shauna Hoare which showed a shared sexual interest in teenage and petite girls".
"Also found at their home were two stun guns, which were prohibited weapons and which may have been intended for the use in the planned kidnap".
Becky died at some point between 11.00am and the early afternoon and her body was put in the boot of Matthews' Vauxhall Zafira car before his mother Anjie Galsworthy returned home from a hospital appointment.
Mr Mousley said CCTV footage showed Matthews and Hoare driving home to Cotton Mill Lane shortly before 7.00pm, with a child captured on camera sitting in the rear of the car.
They then ordered a Chinese takeaway from Laws Kitchen - where Matthews worked - before settling down to watch the television for the night.
"All normal behaviour, other than they had a dead body on their hands," Mr Mousley said.
Karl Demetrius (29) and his girlfriend Jaydene Parsons (23) have pleaded guilty to assisting an offender, but they maintain they "did not know or believe" that bags they helped move contained Becky's body.
Donovan Demetrius (29) - Karl's twin brother - and James Ireland (23) both deny assisting an offender.
