Traffic Enforcement in San Diego, California an Analysis of SDPD Vehicle Stops in 2014 and 2015
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Traffic enforcement in San Diego, California An analysis of SDPD vehicle stops in 2014 and 2015 Joshua Chanin, Megan Welsh, Dana Nurge, and Stuart Henry San Diego State University November 2016 TABLE OF CONTENTS EXECUTIVE SUMMARY .................................................................................................................. ii ACKNOWLEDGEMENTS ............................................................................................................... vii LIST OF TABLES ........................................................................................................................... viii LIST OF FIGURES ........................................................................................................................... xi CHAPTERS 1. Introduction ................................................................................................................. 1 2. PolicinG in San DieGo .................................................................................................... 3 3. Description of the Data ............................................................................................. 14 4. The Decision to Initiate a Traffic Stop ........................................................................ 26 5. EvaluatinG Post-Stop Outcomes ................................................................................ 48 6. Summary and Recommendations ............................................................................. 68 APPENDICES 1. Detailed data on SDPD staffinG and crime in San DieGo ............................................ 93 2. The San DieGo Police Department Vehicle Stop Data Card ....................................... 95 3. SDPD Officer Survey .................................................................................................. 96 4. LimitinG the veil of darkness analysis to stops involvinG movinG violations ............ 104 5. LimitinG the veil of darkness analysis to stops involvinG male drivers .................... 108 6. Division-level traffic stop patterns, by year ............................................................. 112 7. UsinG loGistic reGression to model post-stop outcomes .......................................... 118 8. DescribinG matched and unmatched drivers ........................................................... 121 9. ModelinG driver hit rates after droppinG missinG contraband cases ....................... 127 10. ModelinG driver hit rates after droppinG missinG contraband cases ..................... 128 11. SDPD officer traininG ............................................................................................. 129 i EXECUTIVE SUMMARY This Report presents the results of an independent analysis of records Generated followinG 259,569 traffic stops initiated by San DieGo Police Department (SDPD) officers between January 1, 2014 and December 31, 2015. This review focused on the extent to which these data reveal Department- and division-level racial/ethnic disparities in (1) the decision to initiate a traffic stop; (2) the decision to issue a citation; (3) the decision to conduct a field interview; (4) the decision to initiate a search; (5) the discovery of contraband; and (6) the decision to make an arrest. Our findinGs can be summarized as follows: • Citywide, disparities between Black and White drivers were evident in vehicle stop data from 2014, but not 2015 or the combined 2014/2015 dataset, while no such disparities were found between Whites and either Hispanic or Asian/Pacific Islander (API) drivers in 2014 or 2015; • Data from both 2014 and 2015 revealed distinct and diverGent stop patterns by driver race/ethnicity in police divisions located above and below Interstate 8; • Citywide and across 2014 and 2015, Black and Hispanic drivers were more likely than White drivers to be searched followinG a traffic stop, and despite facinG higher search rates, were less likely to be found with contraband; • Black, Hispanic, and API drivers were subject to field interviews at Greater rates than White drivers; • No meaninGful difference existed in the rate at which drivers from each racial/ethnic Group were arrested; • Black drivers were less likely to receive a citation than White drivers stopped under similar circumstances, while matched Hispanic, White, and API drivers were cited at similar rates; • Records of traffic stops conducted in 2014 and 2015 were often incomplete, raisinG questions as to whether data Generated by the SDPD’s traffic stop data card system are a reliable measure of actual traffic stops conducted; and • City residents who participated in our focus Groups and SDPD officers who participated in an electronic survey and follow-up interviews recoGnized a tension between the Department and minority community members. The remainder of this executive summary provides an overview of the data and analytic methods used to examine traffic stops and post-stop outcomes, a more detailed review of our findinGs, and a brief description of our recommendations to the SDPD to address the identified racial/ethnic disparities. ii Traffic stops To examine the effect that driver race/ethnicity has on the likelihood that an individual will be stopped by the police, we draw on what has become known as the ‘veil of darkness’ technique. This approach is premised on the assumption that if officers are relyinG on driver race/ethnicity to Guide stop decisions, then such bias will be more apparent in dayliGht stops, when a motorist’s race/ethnicity is more likely to be visible, than stops conducted after dark, when physical appearance is harder to detect. The veil of darkness technique, which thus far has been used by police scholars to study traffic stops in six other U.S. locations, allows researchers to avoid the difficulty of identifyinG and applyinG a benchmark against which to compare traffic stop data. This is the central challenGe in the analysis of traffic stops, as the drivinG population in a Given area may look quite different from the residential population. To account for the possibility that the composition of daytime drivers may differ from those on the road at niGht, we limited the analysis to what is known as the ‘inter-twiliGht period,’ or the time period between the earliest end of civil twiliGht (approximately 5:09 pm on Nov. 27) and the latest (approximately 8:29 pm on Jun. 27). FocusinG on this period allowed us to capitalize on a natural experiment produced by seasonal chanGes. Because the sun Goes down much earlier in San DieGo durinG winter months than it does in the summer, people on the road at 6:00 pm in January would experience darkness, but in July the same drive would occur in broad dayliGht. Thus, we are able to compare the likelihood that drivers on the road durinG this 3-hour and 20-minute window were stopped in dayliGht versus darkness, and to be confident that any differences found are due to race/ethnicity rather than other factors. We omitted from the analysis stops that occurred as a result of a suspect description, code enforcement effort, or other type of call for service. By limitinG our sample to only those stops that involve an equipment (e.G., a broken tail liGht) or movinG violation (e.G., an illeGal left turn), we are able to focus on discretionary decisions, where an officer’s use of race/ethnicity may indicate disparate treatment. Our analysis produced a series of mixed results. In 2014, Black drivers were more likely to be stopped durinG dayliGht hours than after dark, compared to White drivers. We found no such disparity in 2015 or in the combined 2014/2015 dataset. Our review of citywide stops involvinG Hispanic and API drivers revealed no disparities in the day-niGht stop patterns of either Group compared to White drivers in 2014, 2015, or the combined total. Put another way, the odds of an Hispanic or API driver beinG stopped durinG iii dayliGht hours are statistically similar to the odds of a stop involvinG an Hispanic or API driver occurrinG after dark, compared to the day-niGht stop patterns of White drivers. To complement our citywide analysis, we also examined division-level stop patterns in 2014 and 2015. Our review of agGreGate data from the five divisions located above Interstate 8 revealed no statistically siGnificant disparities in the day-niGht stop patterns of either Black, Hispanic, or API drivers as compared to White drivers. NarrowinG the focus to the division level, we found evidence of disparities in the day-niGht stop patterns of both Black and Hispanic drivers stopped in the Northeastern division, as compared to Whites. No such disparities were found between API and White drivers, or in any of the other four divisions located above I-8. Data on stops conducted below Interstate 8 in 2014 and 2015 revealed a much different set of results. We find evidence to suGGest that in the agGreGate, Black and Hispanic drivers were less likely be stopped durinG dayliGht hours than they were after dark, as compared White drivers. In other words, when officers on patrol below I-8 were able to see a driver’s race, they were more likely to stop a White driver than either a Black or Hispanic (but not API) driver. At the division level, this type of disparity was evident in stops occurrinG in the Central division and exclusively amonG Hispanic drivers stopped in the Mid-City division. Post-stop outcomes The Report also includes a detailed analysis of the extent to which key post-stop outcomes vary by driver race. In an effort to eliminate other possible explanations