Becky Watts was brutally murdered in a sexually motivated kidnap plot devised by her porn obsessed stepbrother and his cold-blooded girlfriend, a jury have found.
The 16-year-old, described as "a tornado, hurricane and sunbeam all at once", suffered more than 40 injuries as she bravely fought for her life in her pink and white bedroom.
Nathan Matthews and Shauna Hoare had let themselves in to her family's semi-detached house in Crown Hill, Bristol, while Becky was alone during the morning of February 19.
The couple, who fantasied about bringing a teenage girl to the attic of their squalid home less than two miles away, had packed a kidnap kit in the boot of their Vauxhall Zafira.
They bundled Becky's body into their car and left it parked on the family driveway for hours - callously telling her stepmother and boyfriend they had heard her leave earlier.
Detectives admit the truth about what happened to Becky, who was suffocated by Matthews, may never be known.
Matthews bought an £80 circular saw and began to dismember the teenager's body while Hoare coolly sat with Becky's distressed family and searched the internet for when to report her missing.
Over three days Becky's body was dismembered into eight parts by Matthews and Hoare, using the Mac Allister saw, a kitchen knife and a screwdriver.
The pair even watched a parody of Disney's Frozen, entitled Do You Want To Hide A Body, as Becky's remains lay in their bath tub.
The former TA soldier promised a friend £10,000 to store Becky's body parts - carefully wrapped in cling film, bags and tape and packed with cat litter and salt - in his garden shed.
Police officers searched the outhouse in the early hours of March 3, discovering the barbaric truth when a detective unwrapped Becky's severed right hand.
Speaking after the verdicts, Becky's father Darren Galsworthy and stepmother Anjie Galsworthy - Matthews's mother - said her killers should receive the death penalty.
"Nathan was so arrogant he thought he could get away with it," Mr Galsworthy told the BBC.
"That's probably why he chopped her into small pieces and tried distributing her body parts all over the place.
"I loved him like he was my own son, I don't now, I hate him. They need to be put away and not let out. Clearly there is something psychologically wrong with the pair of them.
"There is only one way of paying for the sort of crime they have done and that is by losing their life."
A jury of 10 women and one man at Bristol Crown Court returned guilty verdicts against Matthews and Hoare - finding her guilty of Becky's manslaughter but acquitting her of murder - after three hours and 27 minutes of deliberations.
Becky's friends and family, wearing blue ribbons in memory of the teenager, wept and clutched at each other as the verdicts were returned.
After the first verdict was returned - that Matthews plotted to kidnap 5ft 1ins Becky with Hoare - people in the upstairs public gallery began clapping and shouted "Yes".
Hoare was also convicted of perverting the course of justice, preventing Becky's lawful burial by dismembering and hiding her body and possessing a stun gun. Matthews had earlier admitted them.
After the verdicts, journalists and camera crews crowded the street where the court is located, along with members of the public, police and Becky's family.
The 11-strong jury, who also stood on Small Street, were loudly applauded by supporters of Becky's family.
Matthews and Hoare will be sentenced on Friday, along with Jaydene Parsons, 23, and Karl Demetrius, 30, who owned the shed where Becky's body parts were hidden. The pair had earlier admitted assisting an offender.
Matthews faces a mandatory life sentence but could die behind bars as the sexually-motivated murder of a child can carry a whole life order.
During the harrowing trial, the court heard how Matthews and Hoare swapped messages about kidnapping schoolgirls in the months before Becky's death.
Their laptop contained a sickening 17-minute long rape video depicting a virgin being attacked in her home, with her rapist placing a hand over her mouth.
The trial heard Matthews watched pornography almost daily to satisfy his vile lusts.
Bookmarks on the couple's mobile phones showed an interest in sex with teenage girls and threesomes, which the couple indulged in with a female friend.
Detective Superintendent Mike Courtier described a 16-year-old girl, who Matthews and Hoare lusted after and sent messages to, as "lucky".
"It is speculation to think what potentially could have happened to her or to another similarly attractive young 16-year-old girl but the evidence of the text messages is clear," he said.
Mr Courtier said Matthews had never shown any remorse for what happened to Becky, while Hoare had repeatedly lied about it.
In an insight into his cruel mind, Matthews wrote to his mother from prison, simply informing her that he could not discuss the "facts of the case".
A post mortem examination found that after death Becky suffered 16 stab wounds and a long slash wound to her stomach.
Mr Courtier said Matthews and Hoare had a "sinister" motive relating to their "deep-seated hatred for Becky and their twisted sexual desires".
"The pair carried out their macabre plan," he said.
"They then took her body back to their home and began the horrific and grotesque task of dismembering her over a matter of days.
"It's virtually impossible to comprehend this level of depravity."
Becky's mother Tanya Watts, grandmother Pat Watts and brother Danny Watts said they had been forced to relive the death of their "beautiful, happy, funny, feisty, caring, loyal and witty girl" during five weeks of evidence.
They added: "She was like a tornado, hurricane and sunbeam all at once. She came into your life and made you feel alive."