Signed into law in 2010, SB1070 is a controversial Arizona law that requires law enforcement to verify the immigration status of people they believe are not legal immigrants through the “show me your papers” clause. Many cite that the law increases social costs of both law enforcement and civilians, as well as violates the 4th Amendment by promoting racial profiling. The author of this thesis hypothesizes that law enforcement will stop more Hispanic drivers from checking their immigration status because the unauthorized population in Arizona is largely Hispanic; therefore, this thesis examines the impact of SB1070 on racial profiling behavior by law enforcement.

            The author uses data that details police stops which include information about the county of stop, the race of the subject, and many more variables. The data spans from California to Arizona over the years 2007 to 2018 and is obtained from the Stanford Open Policing Project. The author first examines the stop rates of Hispanic drivers in California and Arizona, focusing on stop rates from 2009 to 2015 in three counties that share a border, which ensures there are no drastic differences in counties. The author then runs a simple linear regression to test if SB1070 significantly influences the rate of Hispanic drivers being stopped. They take into account possible variations in racial profiling in the months directly after the implementation of SB1070’s “show me your papers” clause by examining the six months before and after the implementation in June 2012. This ensures that the tests account for the possibility that racial profiling may average out after the initial implementation of SB1070.

The author notices that, in both states, the number of Hispanic driver stop rates decrease during SB1070’s initial enactment period. While there is not enough data to fully examine this occurrence, the author hypothesizes that law enforcement might have stopped fewer Hispanic drivers to avoid racial profiling allegations. The author also recognizes that while Arizona increased both the number of overall and Hispanic stops, California decreased the number of overall stops and kept the number of Hispanic stops constant.

The other tests show that SB1070 increased the likelihood of a suspect that was stopped being Hispanic by 1.5-1.7%; once the author added controls to the test, the probability increased to 1.9%. Furthermore, tests show that six months after the implementation of SB1070 saw the highest effects of the law. Since the regressions show there is a correlation between SB1070 and the number of stops of Hispanic drivers, the author tests how SB1070 affects the number of citations of Hispanic drivers. Results show that during the enforcement of SB1070, Hispanic drivers were 7.6-7.8% more likely to receive a citation than non-Hispanic drivers. These results show a high level of statistical significance. In regards to arrests, the tests did not show a correlation between Hispanic stops and arrests. However, the author highlights that this might be due to variations in the definition of “arrest.” Furthermore, tests show that Arizona police have a 43% higher chance of issuing a citation than California police.

The author highlights some limitations to the study, such as the assumption that the prejudice of the police is constant and did not increase or decrease in response to SB1070. The author concludes that if SB1070 significantly affects police prejudices, their conclusions about the effect of the bill are still valid. The author also highlights their assumption that Arizona police officers’ perceptions about Hispanic drivers are not influenced by SB1070. Overall, the author concludes that there is strong evidence that SB1070 impacted stops. The tests show a 1.5% increase in the probability that a stopped driver is Hispanic due to the implementation of SB1070. The author quantifies these results, concluding that SB1070 caused 412 stops of Hispanic drivers during the treatment period in the three counties. The author also discusses the costs associated with SB1070. They find that in the studied counties, SB1070 costs around $62,614 in police and suspect resources. There are also other costs the author does not include, such as legal costs and drivers fearing being stopped while driving. Ultimately, the author concludes that SB1070 significantly increases the number of Hispanic drivers being stopped and issued citations. These results are relevant as they provide the opportunity to understand how similar laws implemented in other states impact the U.S. population.