The Claremont serial killings trial has heard how a piece of forensic evidence collected from Ciara Glennon's body was discovered missing the day after it was collected.

Key points: A fibre taken from Ciara Glennon's body was lost after being collected as evidence

A fibre taken from Ciara Glennon's body was lost after being collected as evidence A police officer has admitted touching Ms Glennon's hand while trying to clip her nails

A police officer has admitted touching Ms Glennon's hand while trying to clip her nails It comes as Bradley Robert Edwards' defence attempts to establish examples of evidence cross-contamination

Sergeant Adam McCulloch was responsible for packaging, labelling and storing some exhibits taken from bushland north of Perth where Ms Glennon's body was found on April 3, 1997, and at her post-mortem examination the following day.

Ms Glennon, 27, was the third woman to disappear from Claremont between 1996 and 1997 after Jane Rimmer, 23, and Sarah Spiers, 18, whose body has never been located.

Bradley Edwards is on trial in the WA Supreme Court accused of murdering the three women, with forensic material — including the fingernail clippings from Ms Glennon allegedly containing his DNA — now central to the prosecution case.

'Minute' evidence found on body

Sergeant McCulloch, now a fingerprint expert within WA Police, today gave evidence at the trial and was asked to detail the steps he took at Ms Glennon's post-mortem examination.

Sergeant Adam McCulloch was involved in the DNA examination of Ciara Glennon. ( ABC News: Charlotte Hamlyn )

During the post-mortem, Sergeant McCulloch also assisted in an examination of Ms Glennon's body using a polilight, which can detect things like hair, fibres and semen.

It resulted in a series of exhibits being seized and later stored in a 'drying room' at police headquarters.

Sergeant McCulloch testified that the following day, when he went to collect the samples, he noticed that a yellow top container, said to contain a white fibre, was empty.

Prosecutor Carmel Barbagallo asked him about the nature of that fibre sample.

"They're very small, minute, hard to see with your eye, that's why we used the polilight," Sergeant McCulloch said.

Officer 'touched' Ciara Glennon's hand while clipping her nails

Sergeant McCulloch also admitted he had made contact with the body to assist a mortuary technician who was trying to cut her fingernails.

"I got very close to the point where I actually touched and handled the left hand of Ciara Glennon," he said.

The crime scene on Pipidinny Road in Eglinton where Ciara Glennon's body was found in 1997. ( ABC News )

He told the court he had caught the nail clippings in yellow top containers, before sealing and labelling them.

The prosecution alleges a DNA profile found under Ms Glennon's left middle fingernail and left thumbnail matches Bradley Edwards, claiming it got there when Ms Glennon scratched at her attacker as she fought her life.

It says the same DNA was also found on the 17-year-old victim of the rape at Karrakatta Cemetery in 1995, which Edwards has admitted to.

But Edwards' defence lawyer Paul Yovich argues evidence crucial to the state's case was contaminated while it was in the state's pathology lab and has been attempting to identify flaws in police procedures that may have led to cross-contamination.

Sergeant McCulloch said on the day of Ms Glennon's autopsy he had been dressed in plain clothes but was wearing protective gear provided by the mortuary.

"We were provided with a white overall gown, blue overshoe booties to put over your shoes and a pair of heavy-duty gloves."

Bradley Robert Edwards is on trial accused of being the Claremont serial killer. ( ABC News )

When asked what he knew about DNA technology back in the 1990s, Sergeant McCulloch said his knowledge "very limited" but that had been guided by 'Locard's exchange principle' — which states when two objects come into contact, a transfer of material occurs.

"Whenever we went to a crime scene, the last thing we wanted to do was leave something behind," he said.

Inaccuracies in police officer's statement

Sergeant McCulloch was also involved in the collection of evidence at Karrakatta Cemetery in 1995.

The defence highlighted a series of inaccuracies in witness statements made by Sergeant McCulloch between 1997 and 2019 in relation to both the Karrakatta and Ms Glennon's case.

In one statement from 2015, he had stated that paper bags containing evidence from the Karrakatta scene, including the victim's shorts, had been sealed with evidence tape.

But he admitted to the court that was not the case, conceding the bags had simply been folded over.

Sergeant McCulloch said he had wrongly assumed that the use of evidence tape was common practice in 1995.

"It was brought to my attention from cold case investigation officers and it had been an oversight on my behalf."

He said he then took steps to identify the mistake and corrected it in a later statement.

Mr Yovich acknowledged the sergeant had not intended to be misleading.

"I'm not suggesting you put this in your statement knowingly," Mr Yovich said.

"Quite the contrary, it was an innocent mistake."

Mr Edwards denies the murder charges against him.

His trial is now in its seventh week.