Californian prosecutors say genealogy websites played a key role in tracking down a man accused of being a notorious serial killer.
Joseph DeAngelo, 72, is suspected of being the so-called Golden State Killer, blamed for a spate of murders and rapes in the 1970s and 1980s.
DNA linked the crimes but police had struggled to identify the attacker.
Investigators revealed the search was narrowed with genetic information from websites used to trace family ancestry.
Mr DeAngelo, who was arrested on Tuesday, has been charged with eight counts of murder. He is due to make his first court appearance in Sacramento later on Friday.
Steve Grippi, a prosecuting attorney for Sacramento County, said investigators had compared the DNA they had to information uploaded to genealogical websites by people searching for parents or other relatives.
The DNA Doe Project, which helps trace unidentified murder victims and return them to their families, told the BBC that DNA sent to such a site by a relative of the murderer may have provided a crucial clue to police.
It is not clear if the websites involved were ordered to provide the information or did so voluntarily.