Delroy Forrester admitted killing 11-year-old Jasmine Forrester in February, when he used weapons including a table leg to inflict more than 100 injuries on her at her great-grandmother’s home in Wolverhampton.
The 51-year-old was convicted of manslaughter on the grounds of diminished responsibility by a jury on Thursday. He had denied a murder charge, arguing he was “legally insane”.
During the trial, Wolverhampton Crown Court heard how Forrester had been suffering from a psychotic mental disorder in the days leading up to the attack.
Forrester experienced paranoid delusions, telling relatives and friends he was “getting messages through the TV telling him what to say” and also spoke of demons in his head.
The court heard his daughter, Tyler Forrester, had tried to seek help from a mental health crisis team at a local hospital hours before the incident, but had been told the centre was unable to help.
On the night of the attack, Forrester visited the home of his mother, Victoria Forrester, where he and Jasmine were due to stay that evening.
Once inside the property, he began to attack the elderly Ms Forrester, dislocating her shoulder, before turning on his niece.
The 79-year-old Ms Forrester attempted to protect her great-granddaughter and was able to alert a neighbour to the unfolding tragedy.
Police arrived on the scene and restrained Forrester within minutes, but he had already inflicted unrecoverable head injuries to Jasmine and she later died in hospital.
In a victim personal statement read in court, Jasmine’s father, Simeon Forrester said: “Jasmine was vibrant, funny and loved life.
“That life was tragically cut short by the actions of a family member with whom she should have been safe in a trusting environment.
“I would give anything to change places with Jasmine; to take away the terror and pain she suffered that night.
“For the rest of my life I will feel guilt, because I was not there to protect her when she needed me most.”
Detective inspector Ian Wilkins, of West Midlands Police’s homicide unit, said following the verdict the case was “truly one of the most tragic” he had dealt with during his career.
He added Forrester had been diagnosed with a brain tumour several years before the attack, the treatment for which had left him with epilepsy.
Giovanni D’Alessandro, senior prosecutor for the Crown Prosecution Service in the West Midlands, said: “Jasmine was a friendly, caring and well-liked girl who had a bright future ahead of her. This was all taken away by Delroy Forrester.
“On the night of the murder, he attacked his elderly mother and, while she tried to get help, used a series of improvised weapons to launch a frenzied attack on Jasmine, inflicting serious injuries to her head and body.
“The jury accepted the defendant was suffering from a mental disorder but dismissed his claim he did not know what he was doing was wrong.”
Forrester is due to be sentenced in September.