Since Donald Trump won the Republican Party nomination for president after deriding Mexican immigrants as rapists and criminals, reports of some types of criminal activity from the Latino community to Salt Lake City police have dropped off significantly.

Police Chief Mike Brown fears that undocumented immigrants have receded into the shadows for fear of being deported.

Brown cited a police department analysis of recent data, which comes as a new national report reveals that there are long-term benefits to working with the immigrant community, particularly undocumented immigrants who otherwise may be too frightened to interact with law enforcement. For example, robberies are down in cities where unauthorized immigrants are not fearful that interacting with local police will lead to deportation, the national report says.

There is a true fear out there. I think there are those who are victims and witnesses [in the immigrant community] who sit back and don’t report,” Brown said. “We have to keep reaching out to this community and say we aren’t going to enforce immigration laws.”

Overall, crime is down in Salt Lake City, and therefore reports of criminal activity have decreased. But, in the Latino community, reports of crime have fallen off dramatically. For example, overall crime was down 1.4 percent from January through May 2016 compared with a similar period in 2017. But in the Latino community, it was down 12.9 percent, according to Salt Lake City police statistics.

The difference, Brown said, is not a true reduction in crime. The most telling of the statistics that point to a reluctance to report crime is a 27.7 percent decrease in reports of domestic violence and a 36 percent drop in reports of larceny and theft in the capital city.

Brown said his statistics come from a comparison of crime reports between Jan. 1 and May 31, 2016, to that same time period in 2017.

Shortly after his presidential inauguration in January 2017, Trump issued executive order 13768 that would strip so-called sanctuary cities of federal funding. Although there is no set definition of “sanctuary city,” it refers to local and state policies and laws that limit in some way local police cooperation with federal Immigration and Customs Enforcement (ICE) actions.

These jurisdictions have caused immeasurable harm to the American people and to the very fabric of our republic,” Trump’s order said.

But a December report in the Justice Quarterly by a pair of sociologists disputes Trump’s assertions that sanctuary cities harbor greater numbers of immigrant criminals than other cities.

Municipalities that adopt sanctuary policies for undocumented immigrants do not have higher rates of robbery and homicide than those that cooperate more fully with federal immigration officials. That is the analysis by Ricardo D. Martinez-Schuldt, a doctoral candidate in sociology at the University of North Carolina, Chapel Hill, and Daniel E. Martinez, assistant professor of sociology at the University of Arizona, in their report “Sanctuary Policies and City-Level Incidents of violence, 1990-2010.”

The study is based on crime data from 107 U.S. cities with a population of 100,000 or more between 1990 and 2010.

Our findings suggest that the adoption of sanctuary policy is associated with a modest reduction in robberies over time,” they wrote in Justice Quarterly. They also find that when immigration populations increase within sanctuary cities, the number of homicides and robberies decreases.

Among the reasons for the phenomenon, Martinez-Schuldt said, is that most immigrants are upwardly mobile and focus on jobs and income. Secondarily, he said, immigrants with language and culture in common tend to strengthen disadvantaged communities.

In an interview, Martinez-Schuldt said the study was undertaken to determine if there was any factual basis to Trump’s assertion that sanctuary cities harbor immigrant criminals. Issues surrounding immigrants are highly politicized, he said, citing a 2015 study by the Pew Research Center that found 50 percent of respondents believe immigrants make crime rates worse.

There is no empirical data to support that,” Martinez-Schuldt said.

The Justice Quarterly study bolsters Brown’s view that welcoming immigrants, rather than threatening them, leads to increased reporting of criminal behavior and, therefore, a decrease in crime over time.

Overall, we find modest evidence to support the position held by sanctuary policy proponents that there is long-term benefit to establishing policies that integrate immigrant communities,” the report said, “especially for unauthorized immigrant communities that limit the involvement of local law enforcement in policing immigration laws.”

Salt Lake City officials say Utah’s capital is not actually a sanctuary city. Mayor Jackie Biskupski and the police chief call it a “welcoming city.” But the municipality does have similarities to sanctuary cities in that police do not act as immigration officials and do not seek immigration status from people they encounter.

Like Salt Lake City, Salt Lake County’s Unified Police Department does not ask about immigration status when dealing with the public, said Sheriff Rosie Rivera. UPD emphasizes community policing in which officers interact in a cooperative way with residents to build trust.

But Rivera, who oversees the county jail, said its personnel do cooperate fully with ICE when the federal agency seeks to hold inmates for deportation. During booking procedures, jail staffers determine whether a subject is undocumented, the sheriff said. That information is then forwarded to ICE.

We are not a sanctuary jail,” the sheriff said. “Our process seems to work, and we have not had any complaints.”

Last year, the Salt Lake County Jail had 33,004 bookings. Of them, 253 went into ICE custody for deportation.

Last year, San Francisco, a noted sanctuary city, sued the administration and, in November, Judge William Orrick, U.S. District Court for Northern California, issued a nationwide permanent injunction blocking Trump’s executive order seeking to strip sanctuary cities of federal funding.

In a related matter, Judge Orlando Garcia, of the Western District of Texas, halted most of that state’s ban on sanctuary cities days before it was to take effect in August. San Antonio had sued Texas, arguing the law would diminish law enforcement’s ability to keep communities safe.