TWO sons of a Scots woman found dead off the coast of Crete are to return to the island this week to step up their campaign to find out how their mother died.

David and Michael Porter have also hired one of the leading local criminal lawyers to re-examine all of the evidence and help find clues about what happened to their mother Jean Hanlon.

Dimitris Xyritakis previously represented Englishman John Hogan, from Bristol, who threw himself and his two children from a fourth-floor hotel balcony on the island in August 2006 during a family holiday, killing his son.

Hogan was found not guilty of murder by a Greek court on the grounds he was suffering from temporary insanity to the pressures of his marriage collapsing.

David Porter, 34, said he and his brother Michael, 29, who fly out on Saturday, hope the visit could step up pressure on the authorities.

Ms Hanlon, 53, a former hospital secretary who had been living on the Mediterranean island, was last seen alive on a night out in March 2009, four days before her body was found in the sea.

During their week-long visit, the Porter brothers are planning to hire a private detective to speak to people who saw their mother on the night she died, as well as her friends.

"It's been a very frustrating year – the worst so far really – but we're still determined to press ahead," said David Porter, a hospital porter from Dumfries. "There were developments last year and the year before, but this year nothing seems to have happened."

"Mr Xyritakis is one of Crete's top lawyers, he previously represented John Hogan, and knows the system there very well.

"He's suggested hiring a private eye who can speak to witnesses, and try to find something that was missed in the original investigation – new evidence that could take the case to court."

David Porter last spoke to his mother shortly before she disappeared and she had been in a good mood after getting a new job.

Last year the procurator-fiscal in Dumfries contacted him to offer any help, and the family gave the service a copy of the Greek police file on her death. However, the service was unable to afford the £2500 cost of having it translated.

In July last year the authorities in Crete decided not to charge anyone over the death.

Ms Hanlon, from Dumfries, who was divorced, was found dead off the island's capital Heraklion.

She had been living on the island since 2005, working in bars and restaurants in the coastal village of Kato Gouves.

The investigation has been beset by problems and delays. The local coroner initially ruled she had drowned, a verdict that suggested her death was accidental. However, months later he changed his opinion to declare she had died from a neck injury before her body ended up in the sea.

The last anyone heard from her was after she met a man at a bar in Heraklion, when she called a friend and, speaking in a voice that sounded drugged, said she "wanted to get away".

She later sent a text message with the single word: "Help."

Police identified two suspects – a Greek and a Belgian who were both friends of Ms Hanlon on Crete. The two came under suspicion because of inconsistencies in their statements, but were released after questioning.