Like countless others, MaryAnn Blackmur sent her DNA to be analyzed through an ancestry website, and amid the process, she remembers opting out of, well, something, but she can’t remember exactly what.
“I don’t know. I didn’t want to put it all out there,” said Blackmur, of Hingham.
Hearing how police in California scoured DNA profiles in a database on another genealogy site while hunting for a serial killer, she wishes she had paid more attention.
In-depth news coverage of the Greater Boston Area.
“If you’re not doing anything you shouldn’t be worried, but then it got me thinking more and more," she said.
The way police in California tracked the suspected Golden State Killer has been cause for celebration, and for concern.
It has brought focus to a similar type of testing and search method that some say could put more criminals behind bars.
But privacy advocates worry people of color, who are over-represented in the criminal justice system, could be harassed in DNA sweeps. Or human error could make suspects out of innocent people.
Officials and advocates are wrestling with balancing the reward of catching more violent criminals with the risk of ensnaring the innocent.
“It’s like hitting the lottery,” said Sheldon Krimsky, a bioethicist and professor at Tufts University.
He said the method was ingenious but raises privacy concerns, specifically that police cast can cast too wide a net.
“You’re basically subjecting innocent people to investigation for which they have no probable cause,” he said.
The Golden State Killer is the name given to a serial killer suspected in 12 murders, more than 100 rapes, and dozens of burglaries throughout California from 1974 to 1986.
California investigators had DNA from a crime scene, but they couldn’t find an exact match to a suspect.
So recently they took the DNA profile and plugged it into the site GEDmatch. They were hoping to find a “familial match,” someone in the killer’s family already within the database.
They found the needle in the haystack: a distant relative of the killer. That relative provided the launch point to narrow the list of suspects down to a retired police officer in the family who fit the profile.
To confirm their suspicions, police took trash with the man’s DNA on it for testing. It was an exact match.
Joseph DeAngelo, 72, who lived in Citrus Heights outside Sacremento, was arrested on April 25 as the suspected serial killer.
Privacy concerns have been part of a pushback against a similar type of testing here in Massachusetts.
Researchers said the method lets police drastically narrow their suspect list and could help solve as much as 40 percent more violent crime where DNA evidence exists, but there is no public match.
Dr. Frederick Bieber, a medical geneticist at Brigham and Women’s Hospital, points to a case that made headlines just weeks before the Golden State breakthrough.
Arizona police used familial DNA in a rape and murder case that had gone cold. But instead of using a public genealogy site, they searched more regulated criminal databases and got a hit on a local prison inmate. The suspect turned out to be the inmate’s brother.
“Probably 5 to 8 percent of individuals commit between 50 and 70 percent of reported crime,” Bieber said. “We also know a sad reality that in some instances crime may cluster in families. Not as a genetic trait that’s been inherited but for social or economic reasons.”
Maryland and the District of Columbia have banned familial testing. Two states—Illinois and Louisiana—are considering regulations.
Only 12 states have formally regulated familial testing.
Massachusetts is not one of them, but a State Police spokesperson said the state crime lab lacks the resources, equipment and training to do it.
But, he added that state troopers have used private labs to test for familial DNA in cases like Baby Doe and the Boston Strangler.
Bieber says they should do more.
“We know that there are serial offenders in every state and we need to bring them to justice for the rights of the victims and the future victims,” he said.
A spokesman for the State Police said after the recent successes, they are open to using the testing but would need to study the issue and consult with policymakers.
Private advocates said they will be watching.