Forensic Investigative Genetic Genealogy is an emerging technology in Australia allowing police to compare DNA profiles from multiple crimes to match genetic profiles.
The technique rose to prominence after it was used in 2018 to identify the "Golden State Killer", Joseph DeAngelo, for a string of murders and rapes in California in the 1970s and 1980s.
Thousands of DNA markers are analysed to identify familial relationships, even as distant as third or fourth cousins, allowing police to identify possible suspects in seemingly unrelated crimes.
Genetic markers are compared against two publicly available genealogy databases which allow police access to the profiles of people who consent to their information being used in solving serious crimes.
Detectives in NSW began to review cold case sexual assaults using the technology in 2022, allegedly finding a link between three cases spanning 11 years and 500 kilometres.
The first case involved a girl, aged 11, being ushered into a man's car and then allegedly sexually assaulted in Glendenning in Sydney's west in 1991.
Five years later, a man allegedly offered a 16-year-old girl a lift near Wollongong and then allegedly sexually assaulted her.
Finally, in 2002, a woman, 26, was given a lift by a man and then allegedly sexually assaulted in a park in Dubbo in the NSW central west.
After DNA analysis confirmed the assaults were linked by the same male DNA profile, police uploaded the unknown male DNA profile to two public genealogy databases.
It allegedly identified a close relative of the attacker, leading police to arrest an elderly man in South Kempsey on the NSW north coast on Wednesday.
Robert Wayne Kwan, 77, faced court on Thursday on nine sexual assault and several kidnapping charges.
It's the first arrest triggered by the technology in NSW.
The public can assist in solving further cases by approving police access to their DNA profiles when submitting samples to genealogy websites.
"Advanced DNA technology played a crucial role in leading us to this arrest, and we want to remind the community of the important part they can play in similar cases," Detective Superintendent Jayne Doherty said on Thursday.
"Any DNA accessed through these databases is used solely to help solve the most serious victim-based offences being homicides and sexual assaults or to identify human remains."
The profiles can be accessed for use in solving serious and violent crimes.
Kwan did not apply for bail and will return to Kempsey Local Court on April 22.
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