Thailand backpacker murders: Two Myanmar migrants face death for killing David Miller and Hannah Witheridge

A Thai court has sentenced two Burmese migrant workers, Zaw Lin and Wai Phyo, to death for the murders of British backpackers David Miller and Hannah Witheridge on the holiday Island of Koh Tao. The investigation that followed the murders has been under heavy scrutiny, with serious questions raised over the kingdom's security status for tourists and its criminal justice system.

The verdict comes amid investigating agencies and the Thai police being accused of incompetence, mishandling of evidence and even torture of the suspects. Both of the convicted men claimed torture by police in order to force them to confess to the murders – an allegation that authorities deny. Defence lawyers have also accused the police of bungling their investigation and using the migrants as scapegoats.

Miller, 24, from Jersey, and Witheridge, 23, from Norfolk, were found murdered on the Thai Island of Koh Tao in September 2014. While Miller was struck by a single blow and suffered deep lacerations to his skull before drowning in the shallow surf, Witheridge was raped and then bludgeoned to death with a garden hoe.

The murders made international headlines and Thai authorities came under intense scrutiny, with tourism in the country already suffering from a military coup in May 2014. The police carried out DNA tests on more than 200 people, and many migrant suspects who were detained complained of rough interrogations, with some claiming that they were scalded with boiling water. A fortnight after the murders, a garden hoe and wooden club were classified as the murder weapons.

During the hearing, it was highlighted that there was no independent forensic testing formalities for criminal cases in Thailand and the DNA analysis in this case was conducted by the Thai police. The DNA sample debate that the police used to link the two suspects has been at the heart of the trial, with defence lawyers asking to retest samples taken from the bodies. No independent testing of the DNA sample was done.

Both Lin and Phyo – neither of whom had a criminal record – claimed that they were on the beach on the night of the murders, but that they had gone home after drinking and playing guitar with a friend. Phyo said: "[Police] kicked me in the back, punched me and slapped me; threatened to chop off my arms and legs, and throw my body into the sea to feed the fish.

"They also said they would take me into another room and electrocute me. Police told me that as I had no passport I had no rights, and they told me it had happened before, where Burmese migrant workers were burned in a circle of blazing tyres on Koh Tao island."

In the final sentencing on 24 December, the ruling judge said there was no weight behind the claims by the men that they had been tortured during interrogation by police.

The case had gained international attention, with British Prime Minister David Cameron intervening to ask Thai Junta chief General Prayut Chan-ocha to allow the Metropolitan police to conduct an inquiry in an attempt to reassure the victims' families that the judicial process in Thailand was carried out in a fair and transparent way.

Prayut had enraged many including the victim's families by hinting that at some level the blame lay with the attractive victims. "Will tourists survive in Thailand if they dress in bikinis? They will if they are not beautiful", he said shortly after the murders on 17 September. He later took back the comments after widespread condemnation.