Consumer genetic sequencing, used to provide individuals with data about their ancestry and health, could identify more than half of Americans of European descent from anonymous samples, a new study has found.

The study, published in the journal Science, found that anyone sharing their genetic data online to search for relatives could be unwittingly aiding law enforcement officers in their task.

Yaniv Erlich, the chief science officer of the direct-to-consumer genetics company MyHeritage and study leader, showed how a DNA match, combined with basic information such as age and a reconstructed family tree, could identify an anonymous person who participated in a research project: “Each individual in the database is like a beacon of genetic information, and this beacon illuminates hundreds of individuals – distant relatives connected to this person via their family tree.”

Another study recently proved that even the small amount of DNA stored by police databases could be cross-referenced with consumer genetic data to identify relatives.

While a recent survey found that the majority of the public is in favour of the police using genetic websites to solve violent crimes, the majority of genetic companies have signed transparency guidelines on the issue, and refuse to allow police bodies to search their databases without explicit approval.

Despite the increased transparency, criticisms are still being voiced that those who receive consumer tests as a present may not think about what they are giving away, both about themselves and family members.

However CeCe Moore, an investigative genetic genealogist working with Parabon NanoLabs, said that the study is overly simplistic about how matches are used to find individuals’ identities. She said that while most of the US could be matched to a second or third cousin by an open genealogy database, finding an identity is still difficult without the critical information that was used in the researchers’ sample case.