Two key agencies have come to the same conclusion that the DNA of two Britons who were brutally killed on Koh Tao last year appeared on a hoe believed to be the murder weapon.
But just one, the Central Institute of Forensic Science (CIFS), has publicly announced that the hoe did not contain the DNA of the two defendants, both Myanmar nationals.
"As far as I know, the police report does not mention whether the DNA of the defendants was found on the hoe," Dr Worawee Waiyawuth, a forensic physician at the CIFS, said after testifying before the Koh Samui Provincial Court as a witness yesterday. Khunying Porntip Rojanasunan, director-general of the CIFS, said the police had relied on the tests conducted by the Office of Police Forensic Science.
Three officials from the CIFS yesterday took the witness stand in defence of the two Myanmar migrant workers, 22-year-old Zaw Lin and Wai Phyo.
Despite initially confessing to the double murders, the two defendants now insist they are innocent and that they had been coerced into confession.
The chief judge had allowed Porntip to re-test the hoe at the request of defence lawyers.
"We received the items of evidence for this case on July 17," Worawee said yesterday.
He reckoned that some DNA traces could disappear from the evidence over time.
The shocking murders of the two Britons took place on Koh Tao of Surat Thani province in September last year.
Holder of a doctorate degree from Germany, Worawee yesterday confirmed the credibility of the CIFS by explaining that it had won internationally recognised ISO 17025 certification.
He said an analyst at the CIFS had examined the DNA without knowing whom the DNA samples belonged to and which cases the DNA test results would be used for. After the examination was completed, another official would compare the DNA while fully aware for which case the results would be used.
"Then, I checked all the documents before signing to endorse the results of the test," Worawee said.
Nakhon Chomphuchat, a lawyer for the defendants, yesterday called Pol Colonel Krissada Mitruamsap from the CIFS to the witness stand.
During the court session, Nakhon pointed out that police had not yet examined the underpants of the victims as evidence items. Krissada said the underpants and shorts should in fact be used as evidence.
"They are needed in the process to identify the culprits," Krissada said.
This biology expert has solved many big cases in Thailand before, including the murder of Dr Phassaporn Boonka-whosemsanti, whose body was dissected by her husband. The CIFS has just received the clothing and other evidence for examination.
The families of the two defendants also appeared in the courtroom yesterday. The defendants, throughout the court session, did not show any sign of stress.
Today, a DNA-collection expert from Australia will testify in court in defence of the defendants.