Four men charged with the murder of Karen activist Porlajee "Billy" Rakchongcharoen on Monday lodged a petition with the Office of the Attorney-General (OAG), calling for further collection of DNA evidence to ensure a fair trial.
OAG deputy spokesman Prayuth Phetkhun said the four accused questioned DNA evidence gathered by the Department of Special Investigation (DSI) to build the case against them and urged prosecutors to order the collection of further evidence.
Porlajee went missing on April 17, 2014 while he was helping relatives to sue former chief of Kaeng Krachan National Park Chaiwat Limlikit-aksorn for setting fire to their villages during forest evictions in Kaeng Krachan National Park.
Mr Chaiwat and park officials were earlier charged in connection with his disappearance but the charges were dropped due to lack of evidence. The DSI reopened the case last June and launched a murder probe after finding skull fragments in Kaeng Krachan reservoir.
According to the DSI, nine more bone and skull fragments were retrieved from Kaeng Krachan reservoir in Phetchaburi last year. While a test on mitochondrial DNA from a skull fragment found previously had matched DNA of Porlajee's mother, the new samples did not match.
The nine bone pieces were found 10 metres from the spot where an oil drum was discovered containing Porlajee's skull fragments.
Mr Prayuth said Attorney-General Wongsakul Kittipromwong had been informed of the issue and the petition would be considered by the prosecution's working panel.
Defence lawyer Pornchai Pruekpichailert said the petition challenged the DNA evidence, although he said his clients would not request additional questioning of any witnesses.
The petition with the OAG was lodged after the accused reported to the Central Criminal Court for Corruption and Misconduct Cases, as part of their bail conditions.
The three others charged with murder are Bunthaen Butsarakham, Thanaset Chaemthet and Kritsanaphong Chitthet.