Comparisons between red brick particles found in soil on the strap of Corryn Rayney’s bra and bricks outside the Rayneys’ home were described as “quite remarkable” at her husband’s murder trial today.
Professor Robert Fitzpatrick, a scientist with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) told the Supreme Court trial a comparison between the two samples was “extremely close”.
“There’s a very, very close comparison between the brick fragment and the brick itself,” Prof Fitzpatrick said.
“The comparison is quite remarkable in terms of their pattern, their x-ray diffraction pattern, the broadness, the sharpness and also the mineralogy.”
The bricks particles are relevant to the prosecution case against Lloyd Rayney because they claim that consistencies between particles found in soil on Mrs Rayney’s body and bricks at the Rayneys’ address prove she was killed at home.
Prof Fitzpatrick’s evidence came days after a WA mineralogist told the court there were “many correlations” between mineral components in brick remnants found elsewhere on Mrs Rayney’s body and bricks from her home, two more scientists today gave evidence about particles recovered from her bra strap.
Prof Fitzpatrick and fellow CSIRO scientist Mark Raven took the stand to give evidence simultaneously – an unusual move in a criminal trial.
The decision to put multiple witnesses on the stand at the same time - a practice known in some states as “hot tubbing” - was requested by the prosecution because the two men co-authored reports on their forensic soil investigations.
Those investigations included x-ray diffraction and the use of a Melbourne-based particle accelerator known as a synchrotron.
"Soils are comprised of different minerals and bricks are comprised of different minerals and minerals are comprised of different elements and the power of x-ray diffraction is that it can discriminate between different minerals," Prof Fitzpatrick said.
Mr Raven said the difference between using x-ray diffraction and the synchrotron was effectively that the latter had better separation.
The court was told that some particles recovered from soil on the bra Mrs Rayney was wearing when she died were found to be red brick particles.
Prosecutor John Agius told the court the red brick particles were tested in the synchrotron, with a view to determining "a level of comparability" between the particles on the bra and red brick samples at the Rayneys’ home.
Prof Fitpatrick told the trial that soils can be "very individualistic". However, he also emphasised that “no physical objects will ever be exactly the same”.
“There’ll always be some difference,” he said. “So my fists here, although they come from me, they’ll be slightly different in some way, maybe the fingernails will be different… we accept that there can be a degree of fuzziness,” he said.
Earlier Richard Clarke, a mineralogist at WA’s ChemCentre, told the trial that eleventh-hour experiments performed on bricks taken from the Rayneys’ home only strengthened his view on why brick dust was found in a gouge on Mrs Rayney’s boots.
Before the trial resumed today Mr Clarke, who was giving evidence for a fourth day, spent the morning running an experiment on one of the 34 bricks taken from the couple’s home. The experiment involved using “pencils” topped with different minerals - quartz, feldspar and apatite - each of which has a different value on the so-called mohs scale, which is used by scientists to rank the hardness of different minerals.
“I placed it (the brick) face side up… and I took each of the pencils and I attempted to scribe a mark on the brick and then I examined the marks under the microscope,” Mr Clarke said.
Mr Clarke said each of the pencils made a mark on the brick although the apatite, which is the least hard of the minerals with a mohs value of five, was damaged in the process.
Asked by Mr Agius if the experiment had caused him to have “any reservation” concerning his evidence on the powder, the gouge in the boot and the how the powder may have been formed, Mr Clarke said no.
“I think it supports or strengthens my views,” he said.
Mr Clarke gave evidence last week that scratches on the boots contained bits of quartz, which became stuck as the boot was drawn backwards along a soil-covered brick surface with some force, with the quartz grazing the brick and gathering brick powder in the scratches.
However, under cross-examination yesterday Mr Clarke said he could not say “with certainty” that Mrs Rayney’s boots were dragged across the brick-paving outside the Rayneys’ home.
The trial will resume tomorrow on the fifth anniversary of the day Mrs Rayney’s car was discovered abandoned in Kershaw Street, Subiaco on August 15, 2007.
The discovery was a major breakthrough in the case because the damaged car provided a trail to Mrs Rayney’s Kings Park grave site.
The prosecution’s case is that Mrs Rayney’s car was damaged when it hit a bollard on a Kings Park track.