The body of Miss Horton,21 from Cardiff, was found in the see of the island in Samui. Miss Horton had travelled to Thailand with a university friend for a two weeks holiday.
She had been to the beach with a group of friends on 1 January, close to the bungalows they had rented,when she is said to have wandered away to speak to her mother on her mobile phone and her body found in 12 hours later by a water biker in the sea off Lamai beach in Samui. A post-mortem examination suggested she was raped and beaten before being left in the water to drown. Thai police have alleged the trial of fishermen Bualoi Posit ,23 and Wichai Somkhaoyai,24. The one-day trial on Friday was told that the men had been watching pornographic films on their boat on the evening of 1 January. They then swam ashore using plastic petrol cans as buoyancy and attacked Miss Horton on the beach as she talked to her mother on her mobile phone.
The men hit her about the head and shoulders with a parasol pole and took turns to rape her while the other held her down, the trial heard.
After that they dragged her out to sea to a boat and used that to tow her further out, where the Reading University student drowned.
The court heard that a British tourist, Christopher Burrows, who later found Miss Horton's mobile phone on the beach, heard a faint voice calling out in English: "I'm sinking, I'm sinking."
The suspects appeared in court at Surat Thani on Friday
The discovery of the mobile phone on the beach led police to investigate fishing boats moored offshore, the trial was told.
Thai officers boarded the boats posing as fish traders, before telling those on board DNA tests would be carried out.
The court was told it was at this point the two men on trial admitted they carried out the murder.
The court was told it was at this point the two men on trial admitted they carried out the murder.
The attack took place at 21.00 local time on New Year's Day, close to where Miss Horton was staying on Lamai Beach, on the island of Koh Samui.
Her body was washed up the next morning on a remote beach a few kilometres away where it was found by a water biker.
The trial on Friday heard from eight witnesses, including police officers, forensic doctors and fishermen. The fishermen did not address the court directly, but confirmed their earlier statements admitting guilt.
Thailand's prime minister Thaksin Shinawatra has declared that the men should face the maximum penalty because of damage done to the country's image.
The provisional court of Surat Thani is around 330 miles (520 kilometres) south west of the capital Bangkok.
A Buddhist memorial blessing in Miss Horton's memory was held on Thursday on Lamai beach by the people of Koh Samui.
The provisional court of Surat Thani is around 330 miles (520 kilometres) south west of the capital Bangkok.
A Buddhist memorial blessing in Miss Horton's memory was held on Thursday on Lamai beach by the people of Koh Samui.