A cannabis-addicted teen has been cleared of murder after he stabbed his grandmother to death at her home.
Pietro Addis killed his grandmother, restaurant owner Sue Addis, at her home in Brighton in January 2021, and faced a murder charge over her death.
But the 19-year-old was found not guilty of murder on the grounds of diminished responsibility on Friday.
Addis stabbed the 69-year-old 17 times before leaving her body in a bathtub at her home, before calling 999 to turn himself in.
He told the operators he was "100%" certain his grandmother was dead, but refused to say at the time what his involvement had been.
The then-17 year old claimed to have been suffering from "transient psychosis" when he killed Ms Addis on January 7, a jury at Lewes crown court heard during the course of his trial.
The teenager had been living with Ms Addis at the time due to a dispute with his dad over growing cannabis.
Millionaire Ms Addis was well known in the Brighton community and ran popular Italian restaurants, Pinocchio's and Donatello's, and had become increasingly worried for Pietro's drug use, concerned he was becoming paranoid.
Now 19, Addis pleaded not guilty to murder, but admitted manslaughter.
During the trial, child forensic psychiatrist Dr Peter Misch told the jury Addis couldn’t think rationally at the time.
He said: “Pietro was suffering from paranoid psychosis at the material time.
"It is a state of mind that is extremely abnormal so it impairs rational thinking and is often associated with abnormal beliefs that are not fixed in reality.”
He said that because the psychotic state was "transient", Addis recovered without any treatment or medication and that his condition was likely "drug-induced psychosis" - a part of the “bigger picture of his mental health”.
Addis had also been diagnosed with ADHD in 2018, the court heard, after his grandmother wrote to Dr Daphne Keen expressing her concerns.
"He is suffering paranoia and we are all getting annoyed with him rather than helping," Ms Addis wrote.
"He still says he can't do anything without the Elvanse [his ADHD drug] but with the weed as well he has become impossible to reason with.
"He just wants to sit in his room all day and it is an effort to get him to do anything."
Dr Misch said there was a lot of evidence the teen’s mental health had been declining for some time including reports from family and friends that he was becoming paranoid.
Following the verdict, Surrey and Sussex's Major Crime Team said the killing had been a "tragic case" resulting in the death of a "much-loved and well-respected" grandmother and community figure.
"Our thoughts remain with the Addis family and loved ones who have behaved with dignity and compassion throughout this harrowing ordeal," Det Supt Mark Chapman said.
Addis, of Lancing, West Sussex, will be sentenced on May 5.
