Cold case detectives have finally found the man who committed a “horrific rape” in 2001 – the culprit was already behind bars for another vicious sex attack.

Serial stalker Jason Dockrill, from Stratford, was serving a life sentence for bludgeoning a Finnish student to death in 2003. He had raped and mutilated 23-year-old Suvi Aronen near Wanstead Common, east London.

The convicton meant that the 46-year-old’s DNA was on record so detective revisiting to the 2001 attack quickly came up with a suspect. The stalker initially denied the crime but changed his plea at the Old Bailey sparing his victim the ordeal of re-living traumatic events that happened 15 years ago.

He pleaded guilty to rape and two counts of indecent assault.

Judge Timothy Pontius, who adjourned sentencing until July 18, said on Monday (May 23): ”Having read the statement of the victim, this is a very serious sexual attack. She was in fear for her life.

“It was a stranger rape carried out in a park and it consisted not just of rape but two serious indecent assaults as well.”

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Dockrill, who will be sentenced in July, is already serving a minimum 25 year term for murder. At the time of the murder trial, in 2004, Judge Michael Hyam said the unemployed fitter was “a danger to women and likely to remain so for a long time, if not indefinitely”.

The judge had described the attack as “sexual and sadistic conduct so brutal that doctors consider it exceptional”. Dockrill had attempted to plea diminished responsibility but failed.

The murder of Suvi was made all the more harrowing as her cries were heard by her parents over her mobile phone.

Mum Sirpa, said in a statement to the 2004 trial: “I heard Suvi crying in Finnish and English, ‘Go away, do not hurt me’. I knew something evil was taking place.”

The killing was the culmination of a day of violence. Dockrill had attacked three other women in the hours, including an 80-year-old in same park.