A ferocious killer held his head in his hands throughout a Truro Crown Court hearing which ended on Tuesday with him being given a sentence of detention for life.

Dean Ashley Grainger-Allen was also told by Mr Justice Burnett that he will serve 13 years, less 252 days he had already spent in custody on remand, before the Parole Board can begin to consider when it will be safe for him to be released on licence.

A 20-year-old with a record of senseless violence, Grainger-Allen had pleaded guilty the previous day, when his trial was due to begin, to having murdered 28-year-old Jody Crang, who suffered appalling head injuries on Par sand dunes on July 19, the town's carnival night.

Prosecutor Peter Blair QC told the packed court that while sitting on a bench Grainger-Allen had told Mr Crang in small talk that he had a child, his girlfriend having become pregnant when she was 15, and that he saw his son regularly. Later Mr Crang was shown the defendant's mobile phone on which was a picture of the child.

'Foolishly, it may be said in retrospect, nothing more than an off-the-cuff remark, Mr Crang asked "Are you a paedophile or kiddy fiddler", or something to that effect,' said Mr Blair. 'He said he was only joking, but without warning Grainger-Allen began raining blows on his head. Mr Crang did not respond, almost immediately his head lolling backwards and he might have been semi-conscious at that stage. He was bleeding profusely.'

Mr Blair said that Grainger-Allen smashed a beer bottle and made as if to use it as a weapon but a young man pushed him away.

'The defendant then dragged Mr Crang to the floor and repeatedly kicked, jumped and stamped on his head in the view of a number of witnesses. He returned to Mr Crang and again repeatedly stamped on and kicked his head and neck and spat on the prone body.'

Briefly, said Mr Blair, Grainger-Allen appeared to have a change of heart. Realising the extent of the injuries he had inflicted, he moved Mr Crang into the recovery position, then changed his mind again. At that point he committed another violent act.

The court heard that there were no injuries on Mr Crang's hands and arms to suggest he had attempted to defend himself.

At one point, Grainger-Allen lifted Mr Crang's head and took a photograph of the injuries which he texted to a friend. He then took a passport, birth certificate, bank card and other property from Mr Crang's pockets and he threatened witnesses not to tell the police who was responsible. When arrested, Grainger-Allen told a series of lies, describing the attack as 'disgusting', and was self-critical for not having intervened to stop the attack and tried to claim credit for having put Mr Crang into the recovery position.

Mr Blair said that Grainger-Allen had first appeared before Bodmin Juvenile Court in 2004 and had a number of convictions which involved violence.

The judge asked when Grainger-Allen had first accepted that he was responsible for the death and was told that it was in October.

Defence counsel Sarah Munro QC referred to Grainger-Allen's longstanding personality disorder and said he had been involved in impulsive and violent behaviour from a young age. He was described by experts as grossly immature and lacking in insight and understanding. There was no premeditation, it was a spur-of-the-moment and grossly excessive over-reaction to the suggestion that he was a paedophile. Psychiatrists and psychologists were of the view that while he suffered from a mental disorder it was not sufficient to account for the killing.