Genetic testing services have become enormously popular with people looking for long-lost relatives or clues to hereditary diseases. Most never imagined that one day intimate pieces of their DNA could be mined to assist police detectives in criminal cases.

Even as scientific experts applauded this week’s arrest of the Golden State Killer suspect, Joseph James DeAngelo, 72, some expressed unease on Friday at reports that detectives in California had used a public genealogy database to identify him. Privacy and ethical issues glossed over in the public’s rush to embrace DNA databases are now glaringly apparent, they said.

“This is really tough,” said Malia Fullerton, an ethicist at the University of Washington who studies DNA forensics. “He was a horrible man and it is good that he was identified, but does the end justify the means?”

Coming so quickly on the heels of the Cambridge Analytica scandal, in which Facebook data on more than 70 million users was shared without their permission, it is beginning to dawn on consumers that even their most intimate digital data — their genetic profiles — may be passed around in ways they never intended.