Forensic evidence in the investigation into the rapes of two Melbourne women in the 1980s sat under scientists' desks for months, a court has heard.
Convicted Russell Street bomber Craig Minogue and Peter Michael Komiazyk are each facing 38 charges including abduction by force and rape over attacks on the women, aged 18 and 19, in November 1985 and March 1986.
DNA evidence forms part of the prosecution case, but Komiazyk's barrister Malcolm Thomas on Wednesday grilled a forensic biologist Louise Brown over practices in the lab back then.
Ms Brown admitted DNA wasn't at the forefront of their minds in the 1980s, but items were contained "as much as possible" to prevent contamination.
Lab benches were "wiped down" and gloves were worn, but practices weren't followed as diligently as they are now, she told a committal hearing for the men on Wednesday.
There was no protocol at all for cleaning the microscopes in those days either, she said.
"Certainly from time to time the microscopes were cleaned but there wasn't a process of cleaning between each forensic process," she said.
The court heard evidence items including clothing and swabs were recorded when they were taken for analysis in the lab and when they were returned to storage.
A document has revealed some of the evidence taken from one of the alleged victims was out of storage for more than two months, with no record of when or how many times the exhibits were removed from their sealed packets and examined.
Ms Brown said it was not unusual that a scientist might store items under their desk while working on an investigation in case they wanted to re-test an item, and that multiple items from different cases might be stored there.
She said the items could have been accessed by anybody in the lab, but the policy was "you just didn't handle other people's exhibits".
Ms Brown admitted if two items from two cases were opened at the same time there was potential for contamination, but she didn't expect exhibits in different cases would be mixed up because each was clearly labelled.
"What, for me, would have been of greater concern is contamination if anything fell off a bench onto the packaging of other items," she said.
"The possibility of contamination of the actual item would be fairly slim, but if contaminating material got on the outside it could transfer to the examiners' hands onto other surfaces."
Komiazyk appeared by video link during the hearing while Minogue, who is serving a life sentence over the 1986 Russell Street police headquarters bombing that killed Constable Angela Taylor, did not appear at all.
Ms Brown's evidence is expected to continue on Thursday.