Crime has been declining in many areas across the country for decades, and it continued to do so under Secure Communities. If deportation were an effective crime-prevention method, places that deported the most would display larger decreases in crime than other areas. No trends like that were observed.

But crime data is notoriously noisy, and dependent on a complex range of factors, potentially masking real trends. To counteract some of these possible confounding factors, the authors of the paper took advantage of the program’s staggered rollout to produce data with widely varying conditions.

This natural experiment, in conjunction with models controlling for a variety of demographic and socioeconomic factors, was used to help isolate the potential effect of deportation policy from overall factors and trends in the country. It found no link between higher deportation rates and lower crime.

National spotlight on Nashville

Nashville introduced one of the most aggressive versions of Secure Communities, starting gradually in 2010. By the program’s end in 2014, more than 1,600 people in the city had been deported — almost half a percent of its working-age population.

Since Mr. Trump’s restarting of the program in 2017, the situation for Nashville’s undocumented immigrants has only gotten worse, said Mary Kathryn Harcombe, a lawyer and legal director at the Tennessee Immigrant and Refugee Rights Coalition. She recalled the effect on local law enforcement of Mr. Trump’s early policy memos shifting deportation priorities away from those convicted of serious crimes.

“There was no prioritizing,” she said. “Everybody is fair game. The use of the criminal justice system was no longer based on the concept of, somebody who has committed a crime is more dangerous — it was simply a dragnet system.”

Blurring enforcement priorities heightens the risk of deportation for those with minor convictions, including for misdemeanors like traffic offenses; for violations related only to immigration status, like an overstayed visa; and for those charged with a crime but not convicted. Before Secure Communities was discontinued, a tenth of a percent of Nashville’s working age population had been deported as a result of minor violations — a rate higher than that in 97 percent of areas nationwide.