The Department of Special Investigation (DSI) has enlisted the help of Japanese police to pursue a new lead in the case of a Japanese tourist murdered in Sukhothai almost six years ago.
Tomoko Kawashita was found dead in a small patch of jungle near Wat Saphan Hin in Sukhothai Historical Park on Nov 25, 2007. She was at the park for a Loy Krathong festival celebration.
She had suffered three stab wounds to her throat and one to her waist.
Tambon Muang Kao police found no clues leading to the killer, so proposed to Sukhothai prosecutors in May 2009 that they stop probing the case.
The prosecutors agreed to the request, but asked investigators to reopen the case if more information about the murder surfaced.
In July, the DSI reopened the investigation as a special case after receiving a request from the Tourism and Sports Ministry.
Their review of the case files found that a male Japanese tourist had been spotted near the murder scene around the time the killing was believed to have taken place.
Local police had failed to pursue the lead.
Police are now trying to identify the man so that they can compare his DNA to samples found on the victim's body, DSI director-general Tarit Pengdith said.
Japanese authorities will help the DSI obtain the DNA samples.
Mr Tarit on Wednesday joined Justice Minister Chaikasem Nitisiri to announce the joint investigation.
Mr Tarit said the DSI, Japanese police attached to the Japanese embassy and Sukhothai police commander Rangsan Kotchakrai met in Sukhothai on Tuesday to discuss the case.
The investigators agreed in principle to re-examine the DNA found on Kawashita's clothes, he said, adding that a Japanese court will then be asked to order DNA tests on the Japanese man seen by the witnesses when he is eventually found. He said the original investigation found there were DNA traces of other people on the victim's trousers.
Mr Tarit emphasised that investigators have still not concluded that the Japanese man seen near the murder scene was the killer.
He said the DSI will also work closely with Sukhothai police and will meet every month to monitor progress.
The DSI, prosecutors, forensics police and Japanese police will meet on Oct 25 to discuss ways to obtain DNA samples from the victim's clothes in Japan, he said.
A police source said the murder weapon may not be a fruit knife as was reported in the earlier investigation, but could be a bush knife as the cuts to the victim's throat were deep.
More than 200 people have been interviewed in connection with the case including workers in Sukhothai Historic Park, local security guards, and residents, the source said.
Robbery was believed to be a possible motive for the killing as some of the victim's valuables were missing, the source added.