Becky Watts was murdered by her stepbrother Nathan Matthews and his girlfriend Shona Hoare in a sexually motivated attack, a court has heard.
The 16-year-old went missing from her home in Bristol in February and her body parts were discovered in a shed several days later.
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Bristol Crown Court was told that evidence discovered on telephones and computers connected to Matthews and Hoare "showed a shared sexual interest in teenage and petite girls".
The jury also heard that Becky had told a friend she was scared of Matthews and that he had threatened to kill her and gave "graphic descriptions" of what he would do to her.
Opening the prosecution case, William Mousley QC said the pair killed Becky in her bedroom and then dismembered her in the bathroom, The Guardian reports.
"She was suffocated, despite her fighting for her life," he said. "There followed a deliberate, carefully planned and grotesquely executed plan to cover up her killing."
Becky's mother Tanya Watts left the courtroom in tears as Mousley detailed what is alleged to have happened to her daughter, the BBC reports.
Her body was cut up with a knife and power saw and put into the pair's car before Matthews' mother returned home, the prosecution said.
The pair then went out for a takeaway and returned to their home to watch television. "All normal behaviour, other than they had a dead body on their hands," Mousley said.
Becky's remains were later found in different suitcases and containers in a garden shed near the couple's home, the court heard.
Police also discovered items used in the alleged attack including a circular saw, knife, handcuffs, and the onesie Becky was wearing before she was murdered. The trial continues.