When companies like Ancestry.com and 23andMe first invited people to send in their DNA for genealogy tracing and medical diagnostic tests, privacy advocates warned about the creation of giant genetic databases that might one day be used against participants by law enforcement. DNA, after all, can be a key to solving crimes. It “has serious information about you and your family,” genetic privacy advocate Jeremy Gruber told me back in 2010 when such services were just getting popular.

Now, five years later, when 23andMe and Ancestry both have over a million customers, those warnings are looking prescient. “Your relative’s DNA could turn you into a suspect,” warns Wired, writing about a case from earlier this year, in which New Orleans filmmaker Michael Usry became a suspect in an unsolved murder case after cops did a familial genetic search using semen collected in 1996. The cops searched an Ancestry.com database and got a familial match to a saliva sample Usry’s father had given years earlier. Usry was ultimately determined to be innocent and the Electronic Frontier Foundation called it a “wild goose chase” that demonstrated “the very real threats to privacy and civil liberties posed by law enforcement access to private genetic databases.”

The FBI maintains a national genetic database with samples from convicts and arrestees, but this was the most public example of cops turning to private genetic databases to find a suspect. But it’s not the only time it’s happened, and it means that people who submitted genetic samples for reasons of health, curiosity, or to advance science could now end up in a genetic line-up of criminal suspects.

Both Ancestry.com and 23andMe stipulate in their privacy policies that they will turn information over to law enforcement if served with a court order. 23andMe says it’s received a couple of requests from both state law enforcement and the FBI, but that it has “successfully resisted them.”

23andMe’s first privacy officer Kate Black, who joined the company in February, says 23andMe plans to launch a transparency report, like those published by Google, Facebook and Twitter, within the next month or so. The report, she says, will reveal how many government requests for information the company has received, and presumably, how many it complies with.

“In the event we are required by law to make a disclosure, we will notify the affected customer through the contact information provided to us, unless doing so would violate the law or a court order,” said Black by email.

Ancestry.com would not say specifically how many requests it’s gotten from law enforcement. It wanted to clarify that in the Usry case, the particular database searched was a publicly available one that Ancestry has since taken offline with a message about the site being “used for purposes other than that which it was intended.” Police came to Ancestry.com with a warrant to get the name that matched the DNA.

“On occasion when required by law to do so, and in this instance we were, we have cooperated with law enforcement and the courts to provide only the specific information requested but we don’t comment on the specifics of cases,” said a spokesperson.

As NYU law professor Erin Murphy told the New Orleans Advocateregarding the Usry case, gathering DNA information is “a series of totally reasonable steps by law enforcement.” If you’re a cop trying to solve a crime, and you have DNA at your disposal, you’re going to want to use it to further your investigation. But the fact that your signing up for 23andMe or Ancestry.com means that you and all of your current and future family members could become genetic criminal suspects is not something most users probably have in mind when trying to find out where their ancestors came from.

“It has this really Orwellian state feeling to it,” Murphy said to the Advocate.

If the idea of investigators poking through your DNA freaks you out, both Ancestry.com and 23andMe have options to delete your information with the sites. 23andMe says it will delete information within 30 days upon request.

By Kashmir Hill for Fusion.net