We published a story Sunday about San Diego’s unique approach to curfew enforcement and cited an analysis of crime data that challenges the program’s impact on crime. This story explains the methodology of our analysis and our findings in greater detail.

What’s a Curfew Sweep?

One of San Diego’s most heralded crime fighting programs is often called a collaborative curfew sweep. Once or twice a month, police swarm inner-city neighborhoods and arrest minors out past 10 p.m.

The kids are brought to a detention facility and connected with their parents and social services. Dozens of law enforcement, school and public officials join in the process, and community volunteers often outnumber police officers.

Why Evaluate Curfew Sweeps?

Through the program in the city’s urban core, police have more than tripled curfew arrests in the last five years and forced hundreds of kids to participate in weeks-long diversion programs, pay fines or fight tickets in court.

When pushed to justify the value of these additional arrests, police and elected leaders have repeatedly claimed the program reduces violent crime involving minors. By removing kids from the streets, police argue, kids are less likely to become victims or perpetrators of crime.

Still, police have never conducted a full analysis of the program’s impact on crime. They’ve only cited citywide crime statistics or anecdotal stories about the impact on select children or families to back up the program’s overall merits.

How Did VOSD Analyze Them?

We examined two metrics of crime frequently cited by police: the number of juvenile victims of violent crime and the number of juvenile arrests.

Violent crime includes all murders, rapes, robberies and aggravated assaults. For arrests, we examined three different levels of seriousness: felony, misdemeanor and status offenses. (Status offenses are the lowest-level crimes like curfew and loitering violations.)

Using public record laws, we obtained five years of crime data from the Police Department. The data included date, time and location information for nearly 40,000 incidents. We wanted to know how crime has changed in different neighborhoods and in different times of day.

Some researchers have previously questioned the value of curfew laws by suggesting that they simply shift crime to places without them or shift crime to different times of the day. We wanted to gauge whether that has happened in San Diego following increased curfew enforcement.

We needed to know the location of each incident to compare how crime has changed in areas with and without regular sweeps. Police conduct them in an area stretching from downtown to City Heights to southeastern neighborhoods like Lincoln Park.

We also compared city- and state-wide crime trends for juvenile arrests. Detailed statewide statistics on juvenile crime are posted online by the California Department of Justice.

While San Diego more than doubled curfew arrests between 2007 and 2010, statewide law enforcement agencies went the other direction, cutting curfew arrests in half. The statistics illuminated the uniqueness of San Diego’s tactics. We wanted to test whether it also correlated with unique results.

One last note: For our neighborhood-level analysis, we examined crime during curfew hours and all hours of the day. For the statewide comparison, we only examined crime during all hours of the day because comparative statewide data for curfew hours was not immediately available.

Any Significant Caveats?

The Police Department said it was updating its system for tracking crime statistics and was unable to immediately provide crime data for November and December 2011. Rather than wait several weeks, we projected monthly totals using historical data to fill in the gaps.

Our projection assumes the number of crimes in 2011 included the same proportion of crimes for November and December as the previous year. We used this method rather than annual averages because crime tends to fluctuate seasonally.

What Did VOSD Find?

Our data analysis challenges the claim that San Diego’s curfew sweeps are responsible for a reduction in juvenile crime. Law enforcement officials have reported equal or better results in places without the city’s unique program.

While juvenile crime has plummeted across San Diego during curfew hours in the last five years, our analysis shows that areas without regular curfew sweeps have noticed bigger drops in crime. For misdemeanor arrests, the presence of curfew sweeps correlates with slightly more crime, not less.

If you have any questions about our analysis of the city’s curfew sweeps, contact me directly or post a comment below. I’ll try to respond as soon as possible.

Keegan Kyle is a news reporter for voiceofsandiego.org. He writes about local government, creates infographics and handles the Fact Check Blog. What should he write about next?

Please contact him directly at keegan.kyle@voiceofsandiego.org or 619.550.5668. You can also find him on Twitter (@keegankyle) and Facebook.

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