Her testimony contradicted what police witnesses told the court during the first three days of the trial on July 8-10: that only four items were available for re-examination because other key pieces of evidence, such swabs of DNA taken from the victims’ bodies, were "used up."
Yesterdayʼs (July 23) witness, a scientist from police’s forensic division named Kewalee Chanpan, said that "all" genetic material tested in the lab is replicated for future processing.
Pol Lt Col Kewalee, who was in charge of testing several items in the investigation, also said that original pieces of evidence, such as a condom found at the crime scene, are still in police custody, though she added that DNA traces on objects diminish over time.
The availability of more forensic evidence is seen as a huge victory for the defense team, which has repeatedly protested their inability to access the alleged DNA match that police say incriminates the two suspects, whose names are Zaw Lin and Wai Phyo.
Police’s internal processing of the forensic tests – which were conducted privately in police lab – and the prosecution’s efforts to evade an independent re-examination of the evidence have fed long-running suspicions that the two Burmese migrant workers were framed.
In court this week, the two men, who must wear metal shackles around their ankles, have appeared engaged with the proceedings, but generally relaxed inside the courtroom.
Although the forensic witness said yesterday that all genetic material is replicated as a matter of protocol in the police lab, she did not specifically confirm which samples can be retrieved for further examination.
According to the prosecution, the key pieces of incriminating evidence are semen found in the female victim’s body, and DNA on cigarette stubs found close to the crime scene.
The defense team told Khaosod English that they will discuss which pieces of additional evidence they would like send to the Central Institute of Forensic Science, a lab administered by the Ministry of Justice.
"We have to be specific about what we want retested, and for what purposes," said Nakhon Chompuchat, one of the defendants’ lawyers. "But at least our perception of things is now clearer."
He said the institute is still processing the items that were sent for a retest earlier this month, which included the bloodied garden hoe police believe was used in the murder, and a shoe, sock, and bag found at the crime scene.
Pol Lt Col Kewalee, who conducted police’s original testing of the garden hoe, told the court yesterday that only Witheridge’s blood was found on the weapon. No other DNA was found on the tool, she said.
When pressed by the defense about why there was no DNA found on the hoe that matched the suspects, who presumably had to grip its handle tightly, Pol Lt Col Kewalee said that skin cells from the hand are not as likely to adhere to an object as blood.
She also did not supply the full documentation of the results she gathered in her forensic testing, citing a policy that bars scientists from providing investigative officers with detailed graphs of a person’s genetic makeup.
The defendants’ lawyer, Nakhon, said he was suspicious of this reasoning, and has requested access to all of the material in order to ascertain whether any documents were tampered with.
"The prosecutor tried to be evasive by saying that no law supports giving the graphs and tables to the investigative officers, which is true," he said. "But once you testify to the court, you must show them."
He added, "I have already requested this information, but they won't give us. That is why I am suspicious."
According to Nakhon, the defense has not received a number of requested documents from the prosecution, including photographs taken during the post-mortem examinations, and required paper trails – known as a ‘chains of custody’ – that document the collection, movement, and current location of all physical evidence.
"We haven’t received any of this," he said.
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