Bullied at school for his stilted speech and learning difficulties, teenage killer Paul Smith was always seen as the "odd kid".
Like many sufferers of Asperger's Syndrome, the 18-year-old lacked social skills and hated crowded situations such as the fateful party last December.
He had a fiery temper and when Rosie May Storrie started innocently making fun of the older boy, he lost control and smothered the 10-year-old to death.
His loyal parents, Nigel and Susan Smith, claimed from the start their "vulnerable" son had been blamed for the killing because he was an "easy target".
They said ever since he was a young child he was used as a scapegoat because his condition, a form of autism, made him different from other children.
But he was the last person seen with the ballet star at the party and was incriminated by traces of his DNA found on a can of Guinness at the little girl's bedside.
A common perception of Asperger's sufferers is that they are honest and trustworthy. Smith maintained from the very start that he had not touched the youngster.
In the witness box at Nottingham Crown Court he showed no emotion and spoke in a monotone as he described his version of events on December 28 last year.
The teenager, who left school shortly after his 16th birthday to join his uncle's firm as an apprentice electrician, was only occasionally visibly frustrated as he was accused of attacking the youngster.
But Smith, who was 17 at the time of the tragedy, was polite and controlled despite what defence counsel Mrs Oldham termed his "unusual" demeanour.
Experts have found no link between Asperger's Syndrome and violent crime and traditionally sufferers were said to be more likely to become victims than offenders.
However, a lack of empathy with others and an inability to understand the consequences of their actions could lead an aggressive sufferer to lose control.
Asperger's was first identified as a separate condition in 1944 by a German doctor, Hans Asperger, who spotted similar, odd behaviours in more than one of his patients.
The subtle characteristics which make up the condition often lead to it being missed by doctors who might spot the more noticeable deficits of other types of autism.
Smith was diagnosed at the age of 12 or 13 following a spate of disruptive behaviour at his school.
Telegraph | News | Paul Smith, the 'odd' kid' turns killer
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