BANGKOK (Reuters) - Forensic evidence backs up the confessions of two Thai fishermen that they raped student Katherine Horton and left her to drown on the holiday island of Koh Samui, police said on Monday.
Police said DNA samples taken from Bualoi Posit, 23, and Wichai Somkhaoyai, 24, matched DNA found in semen in the body of the 21-year-old Reading University student.
The two men face murder charges which could bring them the death penalty.
"Doctors have confirmed that sperm found in Katherine matched the DNAs from Bualoi and Wichai, whom we have other evidence against, like their confession and scratches on their bodies," Police General Preophan Dhamapong told a news conference.
Both men, flown to Bangkok for forensic tests after being arrested early on Monday, confessed they had killed Horton, but Wichai denied he had raped her, Preophan said.
Police said a tipoff from a British couple, who said they had heard an X-rated movie from fishing boats floating 100 metres (yards) offshore, led to them interviewing more than 30 fishermen, who said Bualoi and Wichai had boasted of raping the woman.
"They said they watched the movie while drinking, then swam naked on empty barrels ashore and found the victim walking alone on the beach," National Police Spokesman Ajiravid Subarnbhesaj quoted the two men as saying.
"One held her neck and the other beat her with a plank, which also hit his friend, and raped her," Ajiravid told Reuters.
"When they came back to the boat, they boasted to their colleagues that they had just raped a foreigner."
The two men would be charged formally in court later this week, police said.
"We will charge them with conspiring to kill and rape, which will have a maximum penalty of death," chief investigator Aswin Kwanmuang told Reuters by telephone from Samui.
Horton was on holiday on Koh Samui with friends. She had been due to return home this week.
(Additional reporting by Noppawan Bunluesilp)