“California is special,” said David Studdert, a professor and gun researcher at Stanford Law School who focuses on the intersection of law and public health. “It’s not possible to do this kind of work elsewhere in the country. You need to be at the individual and household level to make the connection between the gun and a violent outcome. You can’t measure what you can’t see.”

Studdert, the Stanford professor, said Savani’s acknowledgement was “shocking but not surprising.” He added that he was “impressed by the astuteness of the observation. In my view, that’s the number one problem with gun violence research in the United States.”