A predatory sex offender who attacked women over a 26-year period is due to be sentenced today.
Donald Robertson, 66, was found guilty by a jury at Reading Crown Court of the murder of Shani Warren in 1987 and the kidnap and rape of another victim six years earlier.
Shani Warren's body was found at the edge of Taplow Lake, near Slough, on 18 April 1987. Her wrists and ankles were bound and she was gagged.
Initially, a pathologist concluded that she had died from drowning, with a strong possibility of strangulation beforehand.
It was his opinion that Shani died by suicide, as there were no defence marks or evidence of sexual assault and she could have applied the bindings herself.
Despite these findings, Shani's death was investigated as suspicious, but there was not enough evidence for the police to charge anyone in connection with the case. An inquest in 1987 concluded with an open verdict.
Six years earlier, a 16-year-old girl had been attacked and raped as she was walking home in Slough.
Robertson was arrested at the time but released when the victim did not point him out during an identity parade.
Although she identified him to police immediately afterwards, procedures at the time meant the identification was not considered sufficient to charge the defendant.
Advances in forensic science provided a breakthrough for both cases in the last few years with new evidence being discovered that clearly linked Robertson to these crimes.
When a cold case team at Thames Valley Police reviewed the unsolved case of Ms Warren, further forensic work found traces of Robertson's DNA on the gag found in Ms Warren's mouth - something that hadn't been swabbed in the initial examination - and on her bra.
A pathologist who reviewed the new evidence and the previous pathologist's findings concluded someone else had been involved in her death.
Evidence taken in 1981 from the other victim's clothing was also tested, and a DNA profile matching Robertson was obtained.
Watch: Donald Robertson is asked by police if he'd ever been to Taplow Lake where he replies: "No...not fishing."
This compelling forensic evidence played a vital part in the case presented by the Crown Prosecution Service at trial.
It was supported in Ms Warren's case by accounts of her life and state of mind at the time of her death from witnesses who knew her well.
The prosecution successfully argued that the positive identification of Robertson made by the other victim after she was raped was admissible as evidence.
Robertson's previous convictions for sexual offences, which spanned more than three decades, were also presented as evidence of his tendency to commit crimes of this nature, and that the DNA findings were unlikely to be a coincidence.
Robbie Weber, of the Crown Prosecution Service, said: "Donald Robertson is a dangerous and deadly predatory sex offender who attacked women over almost three decades, using violent threats to get what he wanted. In the case of Shani Warren, he went as far as to take her life.
"Advances in forensic science led to a breakthrough in the unsolved cases of Ms Warren's death and the sexual attack on another young girl, with new compelling DNA evidence clearly linking Robertson to both crimes.
"This evidence played a vital part in the case that we presented at trial which resulted in guilty verdicts.
"Our thoughts are with Ms Warren's loved ones and the other victim in this case who have waited many years to see justice served."
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