Anwar Rosser was a lying, deceitful child who grew into a sadistic psychopath.

Adopted by a professional couple when he was five, he had set fire to a barn using petrol by the time he was 13.

Aged 16, he smashed a trophy into a schoolboy’s face as he lay sleeping, an attack that bore a chilling similarity to the brutal murder of Riley more than 15 years later.

Rosser, usually known as Danny, enlisted in the British Army at 17 and was posted to 5 Regiment Royal Artillery. He did not see active service and was aggressive in drink.

He was imprisoned at a military corrective training centre for being absent without leave and left the Army when he was 21.

He drifted from job to job and had never been in a serious relationship.

By 2005, Rosser was diagnosed with Alcohol Dependence Syndrome. He was violent in drink, shouting at walls and punching them, but quiet and nervous when sober.

In 2010, he was arrested, saying he wanted to kill someone with a knife.

While on a ward at Airedale Centre for Mental Health, he threatened to smash empty beer bottles into the faces of other patients.

He then stayed at a Salvation Army Hostel in Bradford, causing problems with his drink-fuelled anger.

In January last year, Rosser was working as a part-time chef in Denholme. He used a knife stolen from the kitchen to kill Riley.

He took it to Riley’s home that night and carried three further knives from the house upstairs with him.

After the murder, medical experts concluded that Rosser had anti-social personality disorder with psychopathy.

The Crown’s psychiatrist, Dr John Kent, found Rosser presented “an immediate and grave” risk to the public that could involve further acts of sadistic homicide and more child victims.

When he was caught after murdering Riley, Rosser cried when he was handcuffed and whined: “I have ruined my life.”

He later admitted to a nurse that he was the lowest of the low because of what he had done, but he refused to answer any questions when interviewed by the police.