Ten months after two British tourists were killed on a resort island in Thailand, prosecutors called their first witnesses Wednesday in a case marked by claims that the accused — two migrants from Myanmar — were tortured into confessing.

Following widespread attention, the case has been called a test for Thailand's justice system and its treatment of migrant laborers.

The battered bodies of David Miller, 24, and Hannah Witheridge, 23, were found Sept. 15 on the rocky shores of Koh Tao, a scenic island in the Gulf of Thailand known for its scuba diving. Autopsies showed that the young backpackers, who had met on the island while staying at the same hotel, had both suffered severe head wounds and Witheridge had been raped.

Two migrant workers from Myanmar were indicted on several charges related to the murders, and prosecutors say they have a solid case against them that includes DNA evidence linking them to the crime.

The two men — Win Zaw Htun and Zaw Lin, both 22 — were arrested in early October and initially confessed to the killings but then retracted their statements saying they were extracted through beatings and threats, which police deny. Human rights groups repeatedly called for an independent investigation and raised worries that the men might be scapegoats.

The trial on Koh Samui, an island near Koh Tao, began with prosecutors calling witnesses, starting with the first policeman called to the scene and followed by a doctor who examined the bodies.

"We hope the truth will be revealed," defense lawyer Nakhon Chompuchat said as he headed into the courtroom. "We hope the mechanism of justice in Thailand ... will have the same standards of international countries."

From the start, the case raised questions about police competence. Investigators faced a variety of criticism, including their failure to secure the crime scene and releasing several names and pictures of suspects who turned out to be innocent.

Under intense pressure to solve the case, which drew global attention, police carried out DNA tests on more than 200 people on the island.

Worry that the men were tortured by police originated with advocates for migrant workers, who are often abused and mistreated without the safeguard of rights held by Thai citizens. But the allegations caught the attention of the British government, which expressed concern to Thai authorities about the way the investigation was conducted. As a result, British police were allowed to observe the case assembled by their Thai counterparts.

The victims' families traveled to Koh Samui for the trial and issued a joint statement.

Witheridege's family urged the media not to focus on the "speculation, rumor and theory" that has surrounded the case, making "an unthinkable time harder to bear."

Miller's family said that just hours before he died their son had called home and had described the beauty of Koh Tao and the friendliness of the Thai people. "Over the coming weeks we hope to gain a better understanding as to how such a wonderful young man lost his life in such idyllic surroundings in such a horrible way," they said in a statement.

About 2.5 million people from Myanmar work in Thailand, most as domestic servants or in low-skilled manual labor industries like construction, fisheries or the garment sector.

The gruesome killings tarnished the image of Thailand's tourism industry, which has been struggling to recover after the army staged a coup in and imposed martial law in May 2014.

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Associated Press writer Jocelyn Gecker contributed to this report from Bangkok.