A renowned United States forensic genealogist who lent her expertise to the Somerton Man mystery says the investigation was like doing a "Sudoku puzzle".
Colleen Fitzpatrick, a pioneer who has worked on numerous "John and Jane Doe" cases in the US, said she first heard of the Somerton Man in 2013, and met up with Adelaide University researcher Derek Abbott in 2014.
The pair have been working together on the case ever since and now believe the man who was found slumped and lifeless at Adelaide's Somerton Beach in 1948, was Carl "Charles" Webb, a 43-year-old Victorian engineer and instrument maker.
Dr Fitzpatrick told ABC News Breakfast that identifying the man using his family tree was like putting pieces of a puzzle together.
"You come up with a list of DNA cousins — these are people that share DNA with you to some extent — and there might be an aunt or uncle or cousin here and there," she said.
"You don't know who these people are, but what you can do is, you keep trying to find out how they're related to each other and you move them around like the Sudoku puzzle."
"And then finally you find the consistent way they all fit together and the missing piece is the person you're trying to identify."
The DNA used came from hairs in a plaster bust of the man, which the team was given access to by police in 2011.
Professor Abbott told ABC Radio Adelaide the team had been extracting DNA from the hairs since 2011, but by February this year had enough to start comparing it to online genealogy databases.
"We found a hit, we found a very distant cousin, actually in Victoria who was the best match of all of them," he said.
"And then we started from that cousin building out a family tree, finding out that person's parents and grandparents et cetera and building out sideways as well.
"And by June this year we had a family tree of 4,000 people on it."
Professor Abbott said they narrowed in on Charles Webb through a relative on his paternal side.
"Charles Webb is in there, in a family with six siblings and guess what, he sticks out like a sore thumb because he's the only one without a date of death," he said.
Professor Abbott said the team then found a relative on Webb's maternal side to further confirm their findings and it was a "beautiful match".
Could they be wrong?
Professor Abbott said the likelihood of the man's identity being Charles Webb was "99.99" per cent.
"The reason why we don't say 100 is because we're scientists and we never say anything is 100," he said.
He said there was a "small chance" they could be wrong if there was a "twist" in the family tree, such as someone in the family being adopted.
"But when you see this guy with six siblings and he's the only one without a date of death, come on," he said.
There has long been speculation that the Somerton Man was a spy, but Professor Abbott said he was a "pretty straightforward type of guy".
"There's no evidence of that at all, but I'm sure people will keep speculating about that," he said.
SA Police have also been investigating the Somerton Man's identity, and his remains were exhumed last year and given to Forensic Science SA in the hope of recovering DNA.
Professor Abbott told ABC Radio Adelaide he had spoken with SA Police about his findings, and they were "delighted with the news", but the coroner would ultimately make the final determination about the man's identity.
An SA Police spokesperson said the force was "cautiously optimistic that this may provide a breakthrough".
"We look forward to the outcome of further DNA work to confirm the identification, which will ultimately be determined by [the] coroner," the spokesperson said.
