Killer Robert Napper could have murdered schoolgirl Claire Tiltman two decades ago, a court today heard.
Former milkman Colin Ash-Smith is on trial for allegedly murdering the 16-year-old in a "savage and brutal" knife attack in Greenhithe, Kent, in 1993.
But today his defence lawyers claimed Napper, who carried out a string of brutal killings and sex attacks in south London in the early 1990s, could have been behind the "sadistic murder".
David Nathan QC told Inner London Crown Court: "I want to tell you about somebody else. I want to tell you about a man who, between July 1992 and November 1993, a few months either side of the horrific, sadistic murder of Claire Tiltman, killed two young women, both young mothers, and a four year-old child.
"This man was Robert Napper."
Jurors heard that on 15 July 1992 Napper stabbed young mother Rachel Nickell 49 times on Wimbledon Common in front of her two year-old son Alex.
He later savagely killed and mutilated Samantha Bissett before smothering and sexually assaulting her four year-old daughter Jazmine in 1993.
Describing these attacks, Mr Nathan said: "On the night of the 3 November 1993, only a matter of months after Claire Tiltman was killed, he quite literally butchered a young woman of 27 in her flat in Plumstead.
"He stabbed her 30 times in the throat and in her neck and after she was dead he mutilated her body and took part of her abdomen from the flat.
"Not content with that, he suffocated her four year-old daughter."
He said Napper turned his "perverted lust" onto the child, sexually assaulting her before killing her.
Napper was arrested for the double killing, and, using advances in DNA evidence, police were able to discover that he had already killed Ms Nickell.
Mr Nathan said: "During the morning of the 15 July 1992, so only a matter of a few months before Claire Tiltman was murdered, Rachel Nickell was walking on Wimbledon Common with her four-year-old son when Robert Napper stabbed her 49 times in front of her child."
Jurors heard that Napper, who is indefinitely detained in Broadmoor Hospital, also confessed to a string of other rapes and attempted rapes.
Mr Nathan said Napper painstakingly plotted his attacks, and hid weapons at locations in preparation of striking.
And while most of his attacks took place around Woolwich, Mr Nathan said Ms Nickell's killing showed that he was willing to travel to strike.
Mr Nathan said: "If he was prepared to travel all that way to kill Rachel Nickell, why not Greenhithe six months later?"
The court earlier heard Ash-Smith was a knife-obsessed loner who had carried out a "spree" of attacks on women in the late 1980s and 1990s - and plotted more.
He allegedly bragged about his attacks in journals entitled Assault Plans. In 1988 Ash-Smith, then 20, strangled, stabbed and tried to rape a woman, who cannot be named for legal reasons. And in October 1995 he stabbed Charlotte Barnard just 360 metres away from Claire's murder scene.
But Mr Nathan branded the prosecution case "guess work" and urged jurors to put the "terrible" attacks Ash-Smith has previously admitted to out of their minds.
He said: "Can I ask you to put all the terrible things that Mr Ash-Smith has done in the past to one side?
"If you take that out of the equation you can examine what the rest of the prosecution case actually amounts to?"
He added: "Guess work is not enough to find this man guilty of this horrific murder. There is no evidence to support any of his."
Around half a dozen of Claire's old schoolfriends sat in the public gallery to see the beginning of Ash-Smith's defence.
Wearing a navy suit, light grey tie and white shirt, Ash-Smith stared intently at his barrister as he sat in the dock flanked by four officers.
He denies murder.
Mr Nathan said: "I'm not trying to prove that Robert Napper killed Claire Tiltman. I'm seeking to place material before you so you can consider the realistic possibility that he, and not Colin Ash-Smith, did kill Claire Tiltman."
The QC said Napper could have discovered from research that the alleyway where Claire was killed was an "ideal place to lie in wait for his suitable victim".
Mr Nathan added that a train from Woolwich arrived at Greenhithe station at 6.07pm, just before Claire's murder.
Jurors heard that a 12-year-old boy saw a man matching Napper's description near the station minutes after the train arrived.
In a statement to police at the time, the boy said: "There was something about his face that made me look at him. He looked strange. Not angry looking, not frightening, but pulling a face that made him look strange."
Addressing the jury, Mr Nathan said: "Could he have been describing the face of the killer Robert Napper?"
He said Napper could have left the train and walked to the alley to lay in wait for a woman.
He added: "Minutes afterwards, tragically, Claire walked into the alleyway where the killer was waiting and to her death. And if it was Robert Napper, become his fourth victim."
He added: "Could the killer of Claire Tiltman realistically have been Robert Napper? Ultimately, ladies and gentleman, that will be a matter for you to decide."