A SUSPECTED murderer's DNA is on a sample taken from the bra of a woman found bound and gagged in a lake 35 years ago, a court has heard.

Donald Robertson is accused of killing 26-year-old Shani Warren, whose body was found in Taplow Lake, Buckinghamshire, in 1987.

Forensic scientist Rosalyn Hammond carried out tests on samples taken from the crime scene more than three decades ago, Reading Crown Court heard on Monday.

Ms Hammond examined tapings taken from the victim's clothing in 1987, and she also tested a piece of cloth which had been used to gag her.

READ MORE: Doubt cast on suggestion Shani Warren killed herself

Her results suggest "DNA attributable to Robertson" was present on a sample taken from her bra, the court heard.

She also said the gag appeared to have had a blood stain and possibly semen residue on it, as well as "yellowish, gritty staining", jurors were told.

However, a number of other unknown persons' DNA was also found on the samples.

Ms Hammond said this could be caused by people touching or wearing the clothing before Ms Warren died, or by scientists handling them in labs.

For instance, she told the court, from her observation, gloves would "rarely" have been worn in laboratory examinations in the 1980s.

Ms Hammond hypothesised that the defendant's DNA could have somehow "inadvertently" contaminated the taping in a lab after it was taken from the bra.

But she said she had seen nothing to indicate this had happened, the court heard.

Ms Hammond carried out a chemical test on the gag, which she said showed the presence of acid phosphatase, an enzyme which is found in semen.

READ MORE: Man accused of murdering Shani Warren raped girls aged 14 and 17, court hears

Ms Hammond added: "I refer back to my conclusion about the AP [acid phosphatase] reaction where I said, in my opinion, this suggests that AP constituent of semen was still present on the cloth."

Michael Ivers, QC, for the defence, highlighted that the AP enzyme is not just found in semen, citing vegetables, vomit, saliva, pond vegetation or lab contamination as alternative sources.

He also queried the length of time before the results showed up in the chemical test.

The court heard AP results can sometimes show within 10 minutes but this test was left overnight, before a reading was recorded the next morning.

Prosecutor John Price QC told the court: "As everybody knows in this particular case, that gag spent several hours in the waters of Taplow Lake.

"If semen or seminal fluid was deposited on it shortly before it went into the water, would you have expected the water to have diluted its presence?"

Ms Hammond said this would likely be the case.

READ MORE: DNA found in rape victim's underwear, court hears

Ms Warren's GPs, Dr Peter Kersely and Dr Susan Lynch, had provided statements after her death saying they did not think she was suicidal, the court heard.

Their view was supported by Dr Richard Hamilton, of Broadmoor Hospital in Berkshire, who never met Ms Warren but reviewed her diaries for the inquest into her death.

Police reportedly initially treated her death as suicide, despite the fact she was found bound and gagged.

Ms Warren's former housemate, Katherine Whitehouse, had said in a statement that she was "an extrovert who liked going out enjoying herself", the court heard.

A neighbour described her as "bubbly and happy".

Robertson, now 66, who was not in court, denies the false imprisonment, indecent assault and murder of Ms Warren between April 16 and April 19 in 1987.

Robertson also denies the kidnap and rape of a 16-year-old girl, who cannot be named for legal reasons, on July 16, 1981.

This alleged rape took place less than four miles away from where Ms Warren's body was found, the court previously heard.

Robertson also has convictions for raping two girls aged 14 and 17 in separate incidents, and was convicted of burglary with intent to commit rape and kidnap following an incident in Slough in April 1990.

Robertson was charged in October 2021 over Ms Warren's death.

The trial continues on Tuesday.