BANGKOK (AFP) - The defence team for two Myanmar nationals accused of murdering a pair of British backpackers in Thailand confirmed on Sunday that they will not be able to retest crucial DNA samples taken from the victims' bodies.
Migrant workers Zaw Lin and Win Zaw Tun are on trial for the murder of 24-year-old Mr David Miller and the rape and murder of Ms Hannah Witheridge, 23, on Koh Tao island last September.
If found guilty, they could face the death penalty. Both have pleaded not guilty.
Thai police and prosecutors say forensic evidence strongly points towards the two 22-year-old suspects with both men's DNA found on or inside the body of Ms Witheridge.
But the defence claims the men have been scapegoated by an under pressure police force who bungled their investigation and coerced confessions from the pair which they later retracted.
They had asked trial judges on the nearby island of Koh Samui permission to independently retest all the police's DNA samples.
On Friday, the court ruled that they could do so.
But there was confusion about which samples left in police possession were still in a suitable state for retesting - particularly the crucial swabs taken from Mr Miller and Ms Witheridge's bodies.
Lead defence lawyer Nakhon Chomphuchart told AFP on Sunday that only a handful of items found near the crime scene can be reexamined, including a garden hoe - the suspected murder weapon - a shoe, a sock and some plastic bags.
But swabs from the victims were among the DNA samples used up in the testing process.
"We wanted to be able to test more but with the other items there are no samples left (to test)," he said.
It is not clear how useful a retest on the available items will prove to either side. Earlier in the week a witness testified to removing and washing down the garden hoe when he came across it shortly after the holidaymakers' bodies were found.
"The Court order means no possible retest on DNA samples from Hannah and David's bodies," Mr Andy Hall, a Thailand-based British rights activist who has raised money for the accused and advises their legal team, told AFP.
"Zaw Lin and Wai Phyo (Win Zaw Tun) now have no chance to retest crucial Thailand based forensic evidence implicating them in the crimes they are charged of," he said, adding that the integrity of the police investigation "has been seriously undermined" by the lack of retestable samples.
However, Mr Hall said the team plan to introduce evidence at the trial that was obtained in Britain, which they say contradicts the prosecution's case.
"We have seen important evidence from the UK investigation that contradicts certain parts of the prosecution's case but we can't say which authorities have given it to us and what the nature of the evidence is, until it is presented in court," he said.
Ms Witheridge and Mr Miller's bludgeoned bodies were found on Koh Tao's main beach just as Thailand's vital tourism industry was beginning to recover from months of violent street protests that culminated in a May 2014 military coup.
The grim case shone a light on Thailand's many underpaid and often exploited Myanmar migrants who work in the lucrative tourist sector, as well as the country's opaque judicial system, which many Thais complain is weighted in favour of the wealthy or influential.
The trial is taking place over 18 staggered days between now and September, with a verdict due in October.