BANGKOK (Reuters) - Two men from Myanmar convicted of killing two British backpackers on a Thai holiday island in 2014 submitted their final appeal on Monday against the death sentence.

Protesters sit on the road as they protest in support of two Myanmar migrant workers Zaw Lin and Win Zaw Htun in front of the Thai embassy in Yangon December 25, 2015. REUTERS/Soe Zeya Tun

The murder of tourists Hannah Witheridge, 23, and David Miller, 24, sent shockwaves around Thailand and the world, because of the nature of their deaths and the fact the killings took place on an island popular with tourists.

Some migrant rights groups accused Thai police of bungling the investigation and failing to properly seal off the crime scene. Police have defended the probe and the families of both victims have spoken out in defense of the police investigation.

Witheridge was raped and murdered and Miller was beaten and killed. Their bodies were found on a beach on the southern island of Koh Tao in the Gulf of Thailand.

Myanmar migrant workers Zaw Lin and Win Zaw Htun lost an appeal in March to have their sentence overturned after they were convicted by a court on Koh Samui island in December 2015.

“The deadline is today so we have to submit it. This is the final chance to appeal,” Nakhon Chomphuchat, head of the pair’s defense team, told Reuters.

The 2015 conviction was mired in controversy with supporters of the two migrant workers arguing that they had been framed and that they had initially confessed to the crimes under duress.

During the trial, police investigators handling the case were accused by the defense of failing to properly collect and test DNA samples from the scene of the crime.

Prosecutors argued that evidence against the pair was rock solid.

Capital punishment has not been carried out in Thailand for many years.