The male and female pair, who have not been named since they are minors, will be sentenced after Christmas and the presiding judge, Mrs. Justice Yip, said she will impose a "life sentence."
Ghey, 16, was stabbed 28 times with a hunting knife in a heinous premeditated attack in Culceth Linear Park in Warrington, Cheshire in February.
Court documents state that Ghey was stabbed in the head, neck, and back in broad daylight. The two suspects, both 15 years of age at the time of the murder, planned the killing for months in advance and had a list of several other potential victims.
Ghey, whose body was discovered by a couple walking their dogs, agreed to meet the female suspect in a local park when she was killed.
Prosecutors said that in the days leading up to the murder, Ghey's killers exchanged hundreds of WhatsApp messages in which they discussed murder and torture fantasies; the girl admitted to enjoying videos about serial killers, torture, and murder.
A handwritten murder note detailing the planned murder of Ghey was found by police in the girls bedroom after her arrest, according to the Pink News.
Although they intended to murder Ghey, the two individuals told police they had no intention of carrying out their plan; they placed the blame for Ghey's death on one another.
Deputy Chief Crown Prosecutor Ursula Doyle of Crown Prosecution Service Mersey Cheshire said: "The planning, the violence and the age of the killers is beyond belief. Brianna Ghey was subjected to a frenzied and ferocious attack and was stabbed 28 times in broad daylight, in a public park."
"Girl X and Boy Y appear to have been a deadly influence on each other and turned their dark fantasies about murder into a reality," said Doyle.
Nigel Parr, Detective Inspector at Cheshire Police, described the killing outside the courthouse as "a senseless murder committed by two teenagers who had an obsession with murder, whose only motivation in killing Brianna was to experience what this would be like."
The two suspects reportedly had no expression on their faces when the judge read the guilty verdict.
Esther Ghey, the victim's mother, spoke outside the courthouse and said: "To know how scared my usually fearless child must have been when she was alone in that park, with someone that she called her friend, will haunt me forever."
Esther described her daughter as "larger than life, funny, witty and fearless."
Peter Spooner, the victim's father, told reporters outside the courthouse that he knew his daughter was going to be a star, which he attributed to Ghey's following on TikTok.
"It's difficult to comprehend how some people can do these vile things in the world and don’t understand how cruel and heartbreaking their actions can be," he said.
"The impact of Brianna's death has not just affected me as a father, but also my whole family. My heart bleeds every day for Brianna and this will never go away," Spooner added.
