Since an immigrant who was reported to be undocumented was charged in the murder of an Iowa college student, conservatives have seized on the crime as proof of a need for more stringent immigration policies. "You saw what happened to that incredible, beautiful woman [Mollie Tibbetts]," President Donald Trump said at a West Virginia rally on Tuesday. "Should have never happened ... the immigration laws are such a disgrace. We're getting them changed."
Tibbetts, a 20-year-old student at the University of Iowa, was abducted and murdered in July. On Tuesday, law enforcement officials arrested the suspected killer, Cristhian Rivera, who they said was in the country illegally with a stolen identification card, investigators told the Washington Post. (Rivera's lawyer on Wednesday said that he was in the United States legally, according to the Des Moines Register.)
But social science research shows Rivera is an anomaly: Overwhelmingly, studies prove that immigration does not lead to higher crime rates; if anything, it may actually reduce them. Here are some of the studies informing this consensus:
- A 2018 study published in Criminology analyzed population-level crime rates from all 50 states from 1990 to 2014 and found that the relationship between immigration and crime is "generally negative." "Increases in the undocumented immigrant population within states are associated with significant decreases in the prevalence of violence," study author Michael Light writes.
- A 2015 study found that, in the same period, the immigration population more than tripled in the United States; from 1990 to 2013, the violent crime rate decreased by 48 percent, according to Federal Bureau of Investigation data.
- A 2018 study from the Cato Institute found that immigrants have far lower arrest and criminal conviction rates than native-born Americans—a pattern that study author Alex Nowrasteh says holds for all crimes. Homicide conviction rates were 16 percent lower for immigrants than for native-born Americans in Texas in 2015, and criminal convictions overall were 50 percent lower for immigrants.
- Another Cato Institute study looked at prison data, finding that the incarceration rate for native-born Americas was 1.53 percent, compared to 0.85 percent for illegal immigrants and 0.47 percent for legal immigrants.
- A 2014 study of juvenile offenders in the Journal of Youth and Justice found recent immigrants have "significantly lower" rates of violent or property crime, although second-generation immigrants commit crimes at a level more similar to their native-born peers.
These studies are just a sample of a large body of research confirming what immigration advocates have argued for years. "There's 100 years of data from all different sources that all point in the same direction," Walter Ewing, senior researcher at the American Immigration Council, told USA Today. "If you don't believe one study, there's 10 more behind it that say the same thing."
*Update—August 22nd, 2018: This post has been updated to include Rivera's lawyer's statement regarding his client's legal status.