The victim of a brutal murder is said to have been extremely vulnerable and had only one friend in Leeds.
The judge that presided over the trial described Christopher Laskaris, a former pupil at Charterhouse School, a leading independent school in Surrey, as having Asperger Syndrome and bi-polar disorder, meaning he struggled to communicate and interact socially.
The comments by Mr Justice Goss came after his killer, Philip Craig, was sentenced to life behind bars, with a minimum term of 25 years.
He said: "He had only one friend in Leeds. It is clear from the evidence that his difficulties made him vulnerable and he lacked insight into his vulnerability.
"You preyed on this and saw him as someone you could use to your advantage by plying him with drugs and therefore profiting and stealing from him.
"On the night you killed him you stabbed him through the heart with a knife I am quite sure you carried with you."
He added: "The jury rejected any defence of self-defence and found you meant at least very serious harm when you stabbed him. When you left his flat he was dead or dying.
"You subsequently went back and moved his body, by which time you must have known he was dead."
The judge said the effects of the death on Mr Laskaris's family had been "devastating and far-reaching in every possible sense".
He said: "His difficulties in life were not of his making. He needed help and support, not exploitation and abuse."
In a victim impact statement read to the court, Mr Laskaris's sister Cara, a self-employed violinist, said she had been unable to play her instrument since her brother's murder and was now considering a change in career.
And she said she now felt like she was "living in a horror film", as she kept expecting to see someone with a knife every time she looked out of the window.
She said: "It is very hard for me explain what a beloved and thoroughly unique man Christopher was, and what a large, painful hole his violent death has left in our hearts.
"He was sensitive, caring, charismatic and witty, someone who had real individuality and talent. I will never stop loving and missing my brother."
Miss Laskaris said her brother had not accepted his diagnosis of Asperger Syndrome, and had not been given the help and support he needed "despite the worries and relentless efforts of his concerned family."