Brit backpacker, 31, found dead in storm drain after pub crawl on Thailand’s notorious Death Island with girlfriend
They had both been bludgeoned to death.
Other cases where the identities of the deceased are known and the official expiation is unclear or disputed include:
Swiss tourist Hans Peter Suter, 44, went missing on Koh Tao before he was washed ashore at Talay Ngam beach in Lang Suan district of Chumphon province in November 2014.
His family and friends do not believe the Thai government's explanation that the strong swimmer had drowned.
Nick Pearson, 25, from Derby, was found floating dead in the sea off Koh Tao after visiting the island on a family holiday, just two months after Witheridge and Miller were found murdered.
Nick's parents maintain that he was killed in December 2014.
Christina Annesley, 23, from Orpington, South London, was on a four-month trip across Southeast Asia when she died on the island in January 2015.
A British coroner refused to accept the Thai findings into the death.
Dmitri Povse, 29, from France was found hanging from a ceiling on a balcony at Ta Chin Bungalow on Koh Tao at the beginning of January 2015.
His hands were tied behind his back, making it unlikely he had carried out the act himself, but local police dismissed it as suicide.
Russian tourist Valentina Novozhyonova, 23, went missing on Koh Tao in February 2015. She was a strong swimmer who had competed in races but she has never been found.
Luke Miller, 26, from the Isle of Wight, was found dead in a swimming pool at the Sunset Bar at Sairee Beach Koh Tao in January 2016.
Police are said to have told his family he was attacked in a bar the night before he died and post-mortem examination even found head injuries but Thai police ruled he drowned.
Scuba diving instructor Jean Francois Lout, 46, vanished on March 14, 2016, on a boat off the coast of Koh Tao, where he was working.
His body was found two weeks later dumped behind a school on the mainland in Surat Thani province.
Belgian backpacker Elise Dallemagne, 30, was found hanging from a tree in a jungle and half-eaten by lizards on Koh Tao on April 27, 2017.
A series of mysterious events were discovered in the days leading up to the death, including her suitcase boarding a boat, but Thai authorities ruled she killed herself.
Her mother Michele van Egten is certain that Elise was murdered and police are covering up the killer's identity.
Alexandr Bucspun, 33, from Moldova, was found dead in the sea off Had Sai Ree beach on Koh Tao on October 11, 2018. Police never found out how he died.
Bernd Grotsch, 47, was found dead at his home deep in the jungle in the Mae Haad part of Koh Tao in June 2018. He had built up a motorbike rental business that challenged local dominance in the local market.
Police claim he died of heart failure - a theory his family do not believe. They say police refused to provide post-mortem examination reports and they do not believe the findings.
Rocio Leticia Gomez, 39, from Argentina was lost on her first scuba dive in December 2018 on Koh Tao. She was pulled to the surface but died a few days later. Her friends pressed for an investigation but no action was taken.
Multi-millionaire hotel owner Rakeshwar Sachathamakul, 59, and his wife Anshoo, 55, were found dead floating in a hotel swimming pool hours after checking into the resort on Koh Tao in June 2021.
Policee said that CCTV cameras at the luxury hotel were "not functioning" on the day the wealthy couple died.
Neil Giblin, 48, was found dead on January 18, 2023. The circumstances surrounding the death of the healthy and highly experienced scuba diver remain a mystery.