Most people sign up to genealogical websites to find out about their ancestry, but it turns out there's another use for them - and it's raised ethical questions.
Sacramento investigators have revealed this tactic helped identify former police officer Joseph DeAngelo as the man accused of killing 12 people and raping 45 women, between 1978 and 1986.
The actual websites involved haven't been confirmed.
"They managed to track down his extended family network, then by discarding people based on a profile they came up with a pool of suspects," Otago University's Dr Nic Rawlence says.
But websites such as Ancestry.com and My Heritage have grown in popularity and offer DNA analysis services.
Customers send in DNA via a tube of saliva - and in return they get a breakdown of their ancestry.
Officers took DNA from the crime scenes and found a match with DeAngelo's relative who was on the website database.
Undercover detectives then tracked him and collected a new DNA sample, which confirmed him as a suspect.
Dr Rawlence says the investigation method is an "ethical and legal minefield".
"When you've actually handed over your DNA sample you would have not of agreed for your DNA profile to become part of what could be seen as a giant criminal DNA database."
But New Zealand Police insist such a case could not happen here, telling Newshub it would be against the law to use genetic information found on consumer genealogical websites in investigations.