Police in Thailand may have to face an international regulator over the way they handled the investigation into the murder of British backpackers Hannah Witheridge and David Miller, according to NGOs following the case.
International legal and DNA forensics experts have advised Zaw Lin and Wai Phyo, the two Myanmar immigrants sentenced to death over the killings, to make a formal complaint and demand a retrial.
The bodies of Ms Witheridge, 23, and Mr Miller, 24, were found on the island of Koh Tao in September 2014 with severe head injuries.
Ms Witheridge had been raped and Mr Miller had been drowned in the sea after being struck on the head. 
But experts have now alleged that the DNA investigation by the Thai Police Forensics Laboratory was at best incompetent, and in the worst case scenario actually framed the two men.
The trial of the two men has received wide international media attention and raised questions about the handling of the case.