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Why has the case never been solved?

Despite a few new pieces of information emerging over the years, the case is still a mystery.

Most of the key witnesses are now dead.

SA Police told the ABC it was an ?open inquiry? that remained with the Major Crime Investigation Branch.

Genetic testing on the Somerton Man?s hair, embedded in the plaster cast, revealed the man?s mother had European ancestry, but offered no further clues.

Jessie Thomson died in 2007, six years before her link to the investigation was made public.

Rumours swirled that her son Robin was the biological son of the unidentified man.

In 2013, her daughter Kate Thomson said her mother knew the identity of the man on the beach.

?She said to me she knew who he was, but she wasn?t going to let that out of the bag,? she told current affairs show 60 Minutes.

Romance blossomed during investigations

While sleuths around the world have conducted their own investigations over the years, Adelaide University professor Derek Abbott has dedicated more than 20 years to solving the case.

He found himself more deeply involved in the story while researching the connection between Robin Thomson and the Somerton Man.

While Robin Thomson had died by the time Professor Abbott made the connection, his daughter Rachel Egan was alive and living in Queensland.

Professor Abbott contacted her, and before long, the two developed a relationship. They married.

Professor Abbott said comparing the DNA of his wife and the Somerton Man ? her possible grandfather ? could prove whether or not Robin was the Somerton Man?s son and whether Mrs Thomson had been in a relationship with the mystery man.

The only problem?

No state government has agreed to the exhumation. Until now.

Attorney-General Vickie Chapman told the ABC the State Government had offered its conditional support for an exhumation.

But there?s a catch.

?If somebody can come up with the funds to support that, and there is sufficient supervision of this process, then I will consent to it,? she said.

Ms Chapman has had informal talks with police about an exhumation but said they had not indicated it was a priority.

?We would need to have a clear plan as to what the exhumation arrangements would be, what particles of fibre or tissue might be required for forensic assessment, who would undertake that, the security of that, the reinterment,? she said.

?At this stage, I haven?t had any plan presented or indication that there?s finance available, but I would of course act as expeditiously as possible, if those things were in place and approved.?

Could it be funded?

Professor Abbott estimated the cost of an exhumation from the Somerton Man?s grave at West Terrace Cemetery would be $20,000.

It doesn?t sound like much, especially given the level of interest in the case, but a previous crowdfunding effort came to nothing.

?We?ve got the mother?s side, we need the father?s side which is the Y-DNA and we also need the autosomes, which is part of the DNA,? he said.

?That?s what we really want because it?s from [those] that you can use that data to go on genealogical websites and find close cousins.?

Professor Abbott told the ABC he was considering starting a new crowdfunding effort, to help find the answers to the questions he had been asking for more than two decades.

Ms Egan, who said she was only too happy to take part in genetic testing, said she felt a little like Alice in Wonderland ? on the verge of an abyss, not knowing how deep it went.

?There will still be many questions that remain unanswered but hopefully it will give us far more information about who he was,? she said.

?In one sense it?s irrelevant if he?s genetically related or not because obviously he has a connection to my family.

?If we?re not his family, there?s another family out there who deserve to know what?s happened to him.?

While the world watches to see if this mystery will ever come to a conclusion, for Ms Egan it?s personal.

?Is the unknown man my grandfather, or not??

Reporting and research: Daniel Keane
Photography: Tony Hill, Greg Ashman, Chris Lockyer, Carl Saville
Artwork: Ruth Stentiford
Editor: Jessica Haynes
Thanks to: Tim Leslie, Professor Derek Abbott, Gerry Feltus, Wayne Groom, Dr Carolyn Bilsborow, the SA Police Historical Society and the Adelaide Cemeteries Authority