Daniel Ainsley, 24, is seen buying a set of kitchen knives before taking out the biggest one and discarding the rest and casually walking off to kill Mark Wolsey, 48.
CCTV footage captured Ainsley hiding the eight-inch blade in the waistband before killing Mark, who had taken him in when he was made homeless.
Leeds Crown Court heard Ainsley stabbed Mark, a father-of-two, repeatedly and then stood over his body “until his last breath” on March 5.
He then dialled 999 and told a police operator that he had killed a “so-called friend”.
A neighbour was horrified to discover Mark's blood-soaked body with the hilt of an eight-inch chef’s knife protruding from his chest and the blade impaled in his torso.
A post-mortem revealed Mark had been stabbed 15 times during the frenzied attack – nine times in the torso and six times to his upper arm.
Seven of the nine torso wounds penetrated his major organs and he also had 37 superficial knife wounds to his body, the court heard.
Ainsley, a drug addict and alcoholic from Harrogate, denied murder but admitted manslaughter on the grounds of diminished responsibility.
However prosecutors rejected his plea and pushed ahead with a murder trial.
A psychiatric report said his guilt wasn't diminished by his complex personality disorder and the killing was carried out in a “targeted, premeditated and goal-driven” way.
Prosecutor Mark McKone QC said Mark had allowed Ainsley to stay at his bedsit in Harrogate as he was homeless. Ainsley became homeless earlier this year and was kicked out of a shelter for violent and abusive behaviour.
Ainsley and Mark had known each other for over three years and worked together for a brief time at a local food-storage firm, the court heard.
He was admitted to hospital for mental-health treatment and after being discharged, Mark showed him “kindness” and allowed Ainsley to stay at his flat. But he had kicked Ainsley out of the flat because of his behaviour, the court heard.
After stabbing Mark, Ainsley immediately called police and told them he had “stabbed a man to death”.
In a chilling audio recording of the call to the police operator, which was played in court, Ainsley could be heard telling the operator: “I need you to come and arrest me.”
When the operator asks him who has been stabbed, Ainsley replies: “A so-called friend.”
When asked where the knife was, Ainsley replied: “Inside him!”
Ainsley was arrested in Mayfield Grove shortly after Mr Wolsey’s body was discovered at about 10pm.
He said he had knocked on Mr Wolsey’s door and when it was opened slightly, he started stabbing him “and did not stop”. As well as the knife wounds, Mr Wolsey had injuries to his ribs, shoulder blade and hands, which showed he had been trying to defend himself during the savage attack.
Dr Harry Wood, who assessed Ainsley following his arrest, said he'd told him he heard a ghost’s voice “whispering in his ear” and “commanding” him to get a knife and kill Mark.
However, the court heard that Ainsley had given doctors several different accounts about why he killed his former friend.
He had “lifelong” and complex mental-health issues including a borderline personality disorder, paranoia and “hearing voices”. But a psychiatric consultant said Ainsley didn’t meet the criteria for diminished responsibility and that his behaviour in the run-up to the murder was “controlled, purposeful and determined”.
Mark's son Taylor described him as his “best friend" and told the court his life now had a “massive hole in it”. He said Mark loved his granddaughter and she would be deprived of “his father’s fantastic personality and his love”.
Mark's daughter Harley said her father’s death had left a “huge, frightening void” in her life. His mother Jane Smith said her “world had fallen apart” and she had nightmares.
She said her son had a “heart of gold” and would “do anything for anyone, especially if they were struggling or in need”.
Judge Simon Phillips QC said: “Mark Wolsey’s death has had a shattering impact on those who knew and loved him.”
He said the circumstances of his death were “tragic and dreadful to a very high degree”, adding: “He was helpless, vulnerable. He did not stand a chance.”
Ainsley was jailed for life with a minimum term of 21 years and three months in prison. If he is ever released, he will remain on prison licence for life.