Two teenage girls have been found guilty of murdering a 39-year-old woman who was battered in her own home with weapons including a shovel, a TV, a coffee table and a stick laced with screws.
Angela Wrightson had more than 100 injuries on her body following her five hour long ordeal at the hands of the girls, who were 13 and 14 at the time.
During the attack, the pair took selfies of themselves and even posted a picture on social media taken in the police van after the incident.
The girls, who are now both 15, were in tears in the dock after they were convicted at Leeds Crown Court.
Prosecutors said afterwards: "In our society it is hard to imagine that two girls of such a young age could be capable of such violence."
Miss Wrightson was found dead in her blood-spattered living room in Hartlepool, County Durham, in December 2014.
Police said that of her 100 injuries, 25 were made by weapons which included a coffee table, a computer printer, a wooden stick laced with screws, a television set, a shovel, ornaments, a picture frame and a kettle.
The girls' accounts of what happened differed but the jury heard that Miss Wrightson, who was 5ft 4ins and weighed six-and-a-half stone, was assaulted in 12 separate locations around the room.
While at the house, the younger girl made a phone call over Facebook to a friend who heard her say: "Go on (older girl). Smash her head in. Bray her. F****** kill her," as another laughed in the background.
The court heard that the defendants left the house for "time out" at around 11pm, during which time they went to see a friend, covered in blood.
The pair returned to the scene at around 2am and stayed for a further two hours before calling the police to take them home.
The court heard they left Miss Wrightson in an "undignified manner", naked from the waist down on her sofa.
Officers who collected the girls described them as laughing and joking and in "high spirits".
An earlier selfie posted to Snapchat showed the defendants smiling with Miss Wrightson pictured in the background shortly before her death, with further selfies showing the girls drinking cider from a bottle.
The picture taken in the police vehicle was posted to the social media site Snapchat with the message: "Me and (older girl) in the back, on the bizzie van again."
The jury was told that shards of glass and small pieces of gravel or grit were strewn over and around Miss Wrightson's genitals and ash from burnt paper had been put into her ear.
Her living room was described as "akin to a bomb site".
The trial heard that the girls had visited Miss Wrightson, an alcoholic known as "Alco Ange", on a number of occasions as she would buy them alcohol and cigarettes.
On the evening of the murder, they let themselves into her home and asked Miss Wrightson to go to the shop for them.
Both had been drinking before they arrived and the older girl told the court she had taken prescription drugs earlier in the day.
The jury of eight women and four men deliberated for just over three hours before returning the guilty verdicts.
The girls were in tears straight after the verdict and the judge, Mr Justice Globe, asked for them to leave the court.
They later returned to court to be told they will be sentenced on Thursday.
Gerry Wareham, of the Crown Prosecution Service, said: "In our society it is hard to imagine that two girls of such a young age could be capable of such violence.
"The attack that the girls committed against Angela Wrightson was brutal and sustained. One can only imagine the fear and distress that she must have felt in the final hours of her life.
"Given the severity of their assault on Miss Wrightson, one would expect the girls to have shown a degree of remorse in the wake of her death.
"Instead, they laughed and smiled while posing for a 'selfie', with each continuing to deny that they had murdered her throughout the investigation and prosecution of this case."
Detective Chief Superintendent Peter McPhillips, of Cleveland Police, said: "This was a highly unusual and shocking incident. Throughout almost 25 years of service I have never come across such a brutal murder committed by such young girls.
"Angela was subjected to a prolonged, sustained attack and the pathologist identified a significant number of injuries to her body caused by at least 25 blows with weapons."
Miss Wrightson's family said she "had touched the lives of so many people".
In a statement, they said: "No sentence, regardless of its severity, will ever bring Angie back. The two girls responsible will one day be women themselves, free to live their lives and perhaps have children of their own. A right which was taken from Angie.
A Serious Case Review into the case has been commissioned.