UPDATE 4pm: Marks found on the bottom of Corryn Rayney's jeans were "suggestive of drag marks" but it was impossible to say whether her body had been dragged at the Rayneys' Como home or at Kings Park where she was buried, Lloyd Rayney's Supreme Court murder trial was told today.
The forensic evidence underpinning the State's case against Mr Rayney was again scrutinised as mineralogist Richard Clarke took to the witness stand for the second day in a row.
He gave evidence about the marks found near the hem of Mrs Rayney's jeans, and soil and brick particles found on her body, and was questioned about the possibility of a third "scene of interest", based on evidence found inside Mrs Rayney's car.
The defence also renewed its attack on the credibility of the forensic evidence, including questioning Mr Clarke's qualifications and lack of experience in examining damage to footwear after he yesterday said marks on the heel of Mrs Rayney's boots suggested they had been "drawn backwards" over a hard brick surface.
Mr Clarke today gave evidence about marks found on the back of Mrs Rayney's jeans, saying the "V-like formation" was "suggestive of drag marks". Grains of quartz and brick particles were found in the marks.
"The question was where was the dragging event," Mr Clarke said. "Was it at (the Rayneys' house) or could it have been at King's Park?"
Ultimately he said that, based on analysis of soil and brick particles found on Mrs Rayney's jeans, he could not tell whether Mrs Rayney had been dragged at Kings Park or the Rayneys' home.
Mr Clarke, a mineralogist at WA's ChemCentre, was cross-examined by Mr Rayney's lawyer Tony Elliot about the "mobility" of soil, brick, plastic and paint particles that were found on Corryn Rayney's body and how easily the particles might or might not have been transferred.
Mr Clarke said that although some particles were very "light" that did not necessarily mean they were "mobile".
He also gave evidence that, despite apparent similarities in soil samples taken from the Rayneys' Como home, the Bentley Community Centre where Mrs Rayney was last seen alive and Kings Park, where she was buried in a clandestine grave, his method of examination could "achieve very good discrimination".
The court heard yesterday that particles found on the liquidambar seed pods recovered from Mrs Rayney's hair and on her boots were consistent with, and similar to, particles found at the Rayneys' Como property.
The forensic evidence is relevant to the prosecution's case because they claim it proves Mrs Rayney went home after her dancing class on the night she was killed.
The State alleges Mrs Rayney was killed at her home and her body likely dragged across the brick paving and into the back seat of her car.
The prosecution alleges the seed pods came from the liquidambar tree outside the Rayneys' home, while the defence has attacked the forensic integrity of the pods and questioned when and how they were recovered from Mrs Rayney's body.
Mr Elliot questioned Mr Clarke's qualifications to determine the nature of the damage done to Mrs Rayney's boots, including his claim that the damage would have been made relatively recently in the lifespan of the boot because otherwise the particles gathered in the boot scratches would have been dislodged.
He said a lack of overall damage on the boots suggested the heel striations were not from general wear and tear.
Mr Clarke said in response: "That's what we do."
He said he was "not just a mineralogist" but had a background in geology, which helped him to determine "if a material is fresh or otherwise".
Asked about an "extremely irregular" mark on the scuffing next to the boots, which Mr Elliot said was inconsistent with the motion of "this linear dragging", Mr Clarke said he had made note of irregular marks in the reports he prepared for police.
He said he had not specifically examined the mark microscopically but had examined "the whole boot" for any significant evidence.
Separately the court heard about evidence collected from Mrs Rayney's car.
Mr Elliot suggested "purple grains" found on the door sill of Mrs Rayney's car that were not found at either the Rayneys' home or at Kings Park, suggested a possible third "scene of interest".
He said glass, glitter and a bead were also found in the car, which was used to transport Mrs Rayney's body to her bush grave and subsequently abandoned in Subiaco.
Mr Elliot questioned Mr Clarke about soil found on a button attached to Mrs Rayney's shirt that did not match other soil samples. Mr Clarke said he had noted colour variations between the soil found on the button and soil found elsewhere but said the samples were "very similar".
The court was told soil samples were taken from a number of locations around Kings Park, including from Mrs Rayney's grave, from the nearby vehicle track and from a test pit dug by police to mimic a grave.
Mr Clarke said there was some difficulty with samples taken from the test pit, which showed little differentiation between samples taken from surface and those at depth. He said he "got the impression either the soil profile had been previously disturbed or possibly there was a problem when they took the control samples".
Mr Elliot found time to educate court onlookers about Locard's exchange principle: a theory applied to crime scenes that suggests that anyone who commits a crime likely both picks up evidence from the scene and leaves evidence behind.
Quoting from a seminal book on forensic crime investigation, Mr Elliot described the principle as: "Wherever he steps, whatever he touches, whatever he leaves… will serve as a silent witness against him."