A teenager obsessed by serial killers and pornography stabbed a nurse more than 70 times as she took a cigarette break, the Old Bailey has heard.
Cheryl Moss was found in woods near the hospital
Stuart Harling is accused of acting out his fantasies by murdering Cheryl Moss, 33, near St George's Hospital in Hornchurch, east London.
Mr Harling, 19, of Rainham, Essex, denies the murder in April 2006 on the grounds of diminished responsibility.
As the case opened he launched a tirade of insults at prosecution lawyers.
Prosecutor Brian Altman dismissed the claims of diminished responsibility and urged the jury to convict Mr Harling of murder.
He said the defendant was a "loner and fantasist" who spent much of his time playing computer games and surfing the internet to fuel his interest in serial killers, knives, racism and pornography.
Stuart Harling denies murder
"He was just a cold-blooded killer who acted out his fantasy," said Mr Altman.
Mr Altman said the defendant was also interested in Equatorial Guinea and "had the notion of carrying out a military coup".
He told his best friend, Andrew Holland, "they should get 150 people together and take over an oil-rich African country".
Ms Moss, of Dagenham, east London, was attacked in a "frenzied and ferocious" attack as she took a cigarette break.
Mr Altman said: "He struck quickly. His actions had so suddenly and completely overwhelmed her that she had no time to flee and was unable to defend herself.
"She had no time to even scream for help. He fled as quickly as he arrived."
She was found in woods behind the hospital and despite attempts to save her by colleagues who ran to the scene, she was already dead.
Jurors heard how a sports bag containing a long, dark, wavy wig, sunglasses, a sharp hunting knife and an envelope with Mr Harling's address on it was found on a riverbank nearby.
Mr Altman said another hospital worker had seen a man loitering in the area apparently wearing the wig and clothing.
Doctors for the defence diagnosed Mr Harling with Asperger's but rejected claims he was "subject to an abnormality of mind at the time of the killing", Mr Altman said.
Mr Altman said Mr Harling had been planning such a killing for some time and had been on several "dry runs".
He had bought the murder weapon - a hunting knife - on eBay nine months before killing Mrs Moss, the court heard.
Mr Altman said there was also evidence that on the morning after the killing Mr Harling had read about the killing of Mrs Moss on BBC News and Google News websites.
When the trial opened on Tuesday Mr Harling was led away to the cells after a series of foul-mouthed outbursts as Mr Altman outlined the case.
At one point, the trainee accountant said: "I'm going to shoot you with a machine gun."
Michael Wolkind QC, defending, later apologised for his client's behaviour and told the jury: "He is certainly not normal.
"One morning he is a scout leader and altar boy and the next minute he is planning a coup in Equatorial Guinea.
"The coup would have needed a lot of weapons and he initially approached Mrs Moss to steal her car."
The trial continues.