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Big Data on the Beat

from the magazine

Big Data on the Beat

Predictive policing has arrived Winter 2016
Technology and Innovation
Public safety

Predictive policing used to be the future,” said career cop William Bratton, “and now it is the present.” In mid-May 2015, Bratton—the visionary former chief of police in Boston, New York City, Los Angeles, and currently again top cop in New York—was talking about his early days as an officer in Boston, about what worked and what didn’t, and about what can work better in the future. That future will involve predictive policing, which Bratton is bringing to New York (a pilot program was launched last summer).

Predictive policing, which Bratton helped develop when he headed the Los Angeles Police Department during the 2000s, seeks not just to fight crime but to anticipate and prevent it. It uses cutting-edge technology and Big Data—some of which comes from past analysis and some of which is new, streaming in real time to an onboard computer in a patrol car—to identify high-risk areas, which precincts can then flood with police. The aim is not to make arrests but to deter crime before it occurs. Predictive policing relies crucially on community engagement—it can work only when the police are seen as part of the neighborhood, rather than as an occupying presence. At a time when police-community relations are frayed and many cities face rising violent-crime rates as well as renewed concern about terrorist threats, the approach may provide a better way forward.

Currently, about a dozen American cities—including Los Angeles as well as Santa Cruz, Atlanta, Georgia, and Tacoma, Washington—are using PredPol, a leading predictive-policing software and analytics program. Many of these cities rolled out the system over the past few years, and they are seeing positive, and sometimes dramatic, results. In Los Angeles, a nearly two-year study by UCLA crime scholars and law-enforcement officials, released this past fall, found that PredPol successfully predicted—and prevented—twice as much crime as human crime analysts did. The LAPD is now using PredPol in 14 of its 21 divisions.

“Every police department in cities of 100,000 people and up,” says criminologist Craig Uchida, “will be using some form of predictive policing in the next few years.” Like every innovation, the method has advocates and critics. Predictive policing strikes its detractors as potentially Orwellian law enforcement; but at its best, it aspires to something quite the opposite—a return, albeit a high-tech one, to the days of police on the beat who knew their constituents and worked with them to keep neighborhoods safe.

The use of information to respond to crime has always been part of the history of policing, an essential part to solving crime after the fact,” Bratton explains. “When Sir Robert Peel [home secretary in early-nineteenth-century England] created the British Metropolitan Police Force, he had nine principles of policing, which were focused on the prevention of crime.”

Before Peel created the Met in 1838, London was policed by the Bow Street Runners, six officers who constituted the city’s first professional police force and solved crimes as a civic service—not, as professional “thief-takers” previously did, for a fee. The force was founded in 1749 by Henry Fielding, author of Tom Jones. It disbanded in 1839, the year after Peel created the Met as a citizen police presence and an alternative to a military force. The Met’s authority depended on public approval. To Peel, this meant that the police—nicknamed “Bobbies,” for Peel’s first name—had to behave respectfully, succeeding not through compulsion but through the willing cooperation of citizens. Bobbies traditionally didn’t carry firearms; when force was necessary, it was to be minimal. And the police were not the judiciary. Bobbies did not judge guilt or innocence, did not punish or avenge. “The police are the public,” Peel said, “and the public are the police.” Peel believed that the Met proved itself not by the number of criminals it caught but by the absence of crime.

In the United States, policing took shape along Peelian principles: cops walking the city beat deterred crime by their presence. They got to know the neighbors and the neighborhoods, which were more stable than they became after World War II. For years, many cops claimed that the most realistic police show on TV was Barney Miller because it showed the everyday neighborhood problems that most officers dealt with: homicides were rare, and few cops ever had cause to pull a gun. In New York City, you drew your weapon only in life-threatening situations, and, when you did, you shot to kill. The most common response to shooting a dangerous criminal was to vomit. But Barney Miller was an exercise in nostalgia. It was produced just as the system was changing.

Bratton began his policing career in 1970. “It was a time of great transition,” he says. “We were coming out of the 1960s, that time of social turbulence.” Police had become reactive. Instead of a benign presence, designed to prevent crime, they spent more and more time in their squad cars, responding to calls. At a time when people were attacking police, throwing bricks off roofs, using guns and Molotov cocktails, and fomenting revolution in the streets, patrol cars were seen as safer—and more efficient, as budgets became stretched. Officers could cover a greater area more quickly in a car than on foot. Random patrols and responses to calls—counterpunching—supplanted an assigned beat. It was “an ultimately damaging refocusing of the police mission and responsibility,” as Bratton puts it.

The introduction of the 911 calling system, starting in the late 1960s, reinforced the trend to reactive policing, as did a technological revolution in everything from ballistics to serology. The lab replaced the street. Suddenly, cops had a new toolbox of crime-solving techniques. “Policing was professionalized,” Bratton said. There was “better training, better education, and more focus on solving crime than preventing it.”

But the new methods generated new problems: police departments found themselves swamped with the surge in calls coming in because of 911. They couldn’t keep up with the demand for their services. Making matters worse: to save money, cities began cutting back police forces around the country. The Boston PD went from 2,800 officers to 2,000. New York City’s force shrunk from 31,698 in 1970 to 22,588 in 1980, about two-thirds the size of the force today. The police who remained faced many new frustrations, especially with the growing legal emphasis on criminals’ civil rights. The Supreme Court’s 1964 ruling in Escobido v. Illinois (establishing the right of suspects to have a lawyer present during police questioning) and the 1966 ruling in Miranda v. Arizona (requiring police to read suspects their rights before they can be questioned) transformed policing, as did modern legal interpretations of the Exclusionary Rule, which deems inadmissible in court any evidence that police collect in violation of a suspect’s constitutional rights. Cops were overwhelmed, too, by the growth of trafficking in hallucinogens and the various forms of cocaine and by the increasing numbers of young people drawn into the drug culture—abandoning homes and schools, hitchhiking across the country, and living on the streets, in communes, and in squats. Haight-Ashbury and the East Village replaced the traditional skid row. Things worsened during the 1980s. “We were being briefed [in Boston] on this new type of cocaine, crack, that had decimated New York,” Bratton said, “and we were starting to see signs in Massachusetts within a short period of time: whoosh, it was like one of these tsunamis.” Crime numbers climbed to frightening new highs.

Deinstitutionalization compounded the problem. A flood of homeless mentally ill people ended up on the streets, degrading neighborhoods further. Every day, people were confronted with evidence of a crumbling social contract. By the end of the 1980s, Bratton observes, the reactive approach dominated police methods, which focused on improving performance in two areas: responding to 911 calls and investigating major crimes. Police neglected a third: preventing disorder. Urban quality of life was deteriorating, with many neighborhoods overrun with litter, crack vials, prostitution, street people, panhandlers, squeegee men—and broken windows.

In March 1982, George L. Kelling and James Q. Wilson’s soon-to-be-famous article “Broken Windows,” about policing that focused on quality-of-life crimes, appeared in The Atlantic. Kelling and Wilson’s theory was that tolerating disorder soon bred the conditions for more serious crimes, as lawbreakers felt emboldened. In the 1990s, during the early years of Rudy Giuliani’s mayoralty, when Bratton began his first tenure as New York’s police commissioner, a new “Broken Windows” philosophy of policing, with Bratton and Kelling as leading advocates (often in the pages of City Journal), replaced the more reactive approach. Broken Windows targeted misdemeanor offenses and prioritized neighborhood order as an important goal in itself. “Working closely with the community to identify what was creating fear,” Bratton says, police operated on “the recognition that fear was being created not only by serious crime but by quality-of-life crimes.” In arresting low-level offenders, moreover, police often found that they were wanted for more serious felonies. Analysis of “root causes” was left to sociologists. “We believed that the causes of crime were not racism, poverty, the economy, demographics,” says Bratton. “They could be significant influences if not dealt with, but the real causes of crime are people—criminals.”

The Broken Windows theory was reinforced by CompStat, the crime analysis and accountability system that Jack Maple created and instituted in the New York Police Department in 1994, when Bratton began his first tenure as the city’s police commissioner. CompStat, the forerunner of predictive policing, helped Bratton and the NYPD transform a city that had been overrun for decades by crime and disorder. “A wide variety of changes in how patrol resources were deployed in New York City were at the center of the regime initiated by William Bratton and crime analyst Jack Maple and continued for years afterward,” observes Franklin E. Zimring in The City That Became Safe. “Crime analyses and mapping were used to target particular problem areas where patrol, detective, and narcotics units might be emphasized.”

How best to use the large amounts of information the police were processing? “We began to use intelligence-led policing to focus on the prevention of crime,” Bratton said. “And, increasingly, as we got more capacity to get that information in a timely fashion [real time], we were able to stop patterns and trends after the second, third, or fourth incident rather than catching them when they’ve committed 20 or 30 or 40. We had found a way to prevent crime by stopping perpetrators after the second or third act.”

The result of the NYPD’s innovations is well known to City Journal readers: between 1993 and 2000, a drop of 57.26 percent took place in the seven major crime categories, from murder and rape to burglary and auto theft. New York’s success was so striking that many cities across the nation adopted the new methods. Not only was technology offering unprecedented amounts of data; it also was developing algorithms that could analyze the data more quickly, and get the analysis to the cop in the patrol car. Two decades after these practices first became systematized, the building blocks were in place for the next phase of the policing revolution: predictive policing.

The PredPol system works by looking at a specific geographical area. A precinct gets divided up into 500-by-500-foot “boxes,” each about the size of a city block. A box thought likely to be a locus of crime—because of its history, location, current activity, and other factors—becomes a “hot box.” A computer analyzes what crimes have occurred there in the past, what is happening in real time, and other inputs. Even the weather can be a factor: when it’s below freezing, for example, fewer potential criminals come out on the streets.

What sites in the area—schools, strip clubs, bars, malls—might serve as magnets for potential burglars? The cops look at an “intersection of risk factors,” said Megan Yerxa, a crime analyst at the Tacoma, Washington, police department, which fully deployed PredPol in October 2013. They have to look at “a terrain that shows hot areas,” such as places where two cultures rub up against each other, as in New York City, where the Upper East Side abuts Spanish Harlem. Once the hot spots are identified, the police visit them two or three times during a tour, making their presence felt and, by doing so, deterring crime. “PredPol doesn’t take into [account] socioeconomic factors,” Yerxa says. It avoids targeting a particular race or income group, and the statistics tend to hold true for all kinds of neighborhoods. For example, according to Yerxa, residential burglary frequently occurs near high schools and middle schools, and not just in bad neighborhoods. “If a home is broken into in an affluent area,” explains UCLA anthropology professor Jeff Brantingham, PredPol’s cocreator, people mistakenly think that it’s an “outsider,” someone from a poorer neighborhood preying on richer people. But “it’s most likely the teenager down the street trying to impress friends.” Because PredPol focuses not on a city, not on a borough, and not even on a neighborhood, but on a block or a few blocks, it is very specific and localized.

The evidence suggests that crime is predictable, at least statistically, because criminals follow patterns. They tend to go back to work in the same area, the same house or business, because they’re familiar with the setup—and they got away with it the first time. The nearby risk of one burglary, for instance, tends to be 600 feet from the first crime over a period of 14 to 28 days. “An offender hits a neighborhood three times,” Yerxa said—and then tends to go to the next neighborhood over. “They travel to avoid detection, but they don’t travel too far.” The question she asked herself was: “Do the last 28 days predict the next seven days?” How do they predict it? And is there a way to intervene to interrupt the repeating pattern of criminal behavior without violating someone’s civil rights?

Brantingham and his PredPol cofounder George Mohler of Santa Clara University thought it was possible to predict certain crimes, using a system similar to the one that forecasts earthquake aftershocks. Initial crimes are often followed by an “aftercrime”—for instance, a car theft can be followed by a robbery in which the stolen car is used. They developed an algorithm to predict future crime locations. Departments using PredPol look at what has happened recently in a hot box—say, a series of house break-ins before dawn. The local precinct may send patrol cars and beat cops into that box. If the cops spot a known offender—someone with a record of that particular crime at that time of day—and the KO is casing a house, that gives the officer probable cause to stop and engage the suspect and—possibly—to make an arrest. “I’ll stop and talk to a guy,” said Los Angeles Foothill Division assistant watch commander Sergeant Scott Kennedy, “and engage him.” Kennedy tries to create a consensual, not a confrontational, encounter. This is not a dragnet, scooping up anyone who looks suspicious. It is targeted—and it’s used only when there is clear probable cause. “Positive outreach,” according to Tacoma’s senior crime analyst Jackie Shelton, Yerxa’s colleague, “is as important as deterrence.” Community-based services, she says, are important if PredPol is to be effective.

JOHN MINCHILLO/AP PHOTO
“The use of information to respond to crime has always been part of the history of policing,” says New York police chief William Bratton. Now he and other innovators believe that advanced data can be used to prevent crime.

PredPol is based on universal principles. “I got hooked on Moneyball and sabermetrics (Bill James’s revolutionary analytic tool for judging baseball players’ performance),” says Craig Uchida, the criminologist who is also president of Justice and Security Strategies—and a member of the Society of Baseball Researchers. When he worked for the Department of Justice, Uchida oversaw grants to develop predictive-policing methods. He noticed the similarity between baseball and police work. “Look at baseball,” he says. “Baseball collects lots of information about everything. You can create different algorithms for different baseball players and how they perform”—and you can do the same for crime.

Cops have always depended on intuition, Uchida says. Now they can “back up intuition with information—have cops talk with people on the streets to find out what is really happening. Write it down. Turn it into statistics, and then—using new technology that we now have—crunch the shared experience.” The outcome depends on good data. “This is a shift in how you do police work,” he says.

When Bratton called Uchida in 2008 to come out to Los Angeles and work with him and Sean Malinowski, the project manager for the LAPD’s predictive-policing initiative and now chief of staff to Bratton’s successor in L.A., Charlie Beck, Uchida says, “I had no idea what he was talking about. Like everyone else, I was skeptical. But there was something about the LAPD that I liked. There seemed to be something there.” He met Jeff Brantingham, whose parents, Uchida said, were “stars” in the criminology field, formulators of the “environmental crime theory” that looks at what situations cause or prevent crime. It was like the gathering of the gang in The Magnificent Seven: Uchida, Brantingham, Malinowski, all working under Bratton—a happy coincidence of people and project that Bratton creates wherever he goes.

By July 2011, Mohler and Brantingham’s PredPol company was supplying increasingly sophisticated and effective algorithms to the LAPD and about a dozen other police departments. At first, though, the process was rudimentary. “George [Mohler] and Jeff [Brantingham] had a great concept,” notes Santa Cruz deputy police chief Steve Clark, “but they didn’t know how to make it relevant in the police world.” Clark and his analysts would gather crime statistics, enter them as Excel columns, and give each case a geographical coordinate. Brantingham and Mohler then cranked out a map with hot boxes. They refined the algorithms over time.

Clark didn’t understand the math, but he knew what it tried to capture: pockets of crime in three key areas—burglaries, theft from vehicles, and theft of vehicles. Those crimes, he said, “are the ones we felt we could [predict] with a good degree of accuracy. Instead of chasing yesterday’s crime, we used yesterday’s crime to predict where today’s crime is going to happen.”

The Santa Cruz PD started testing the predictive accuracy of PredPol. “In some cases, we were 60 percent predicting where or when,” Clark said. “It blew my mind.” Other jurisdictions were seeing increases in crime; Santa Cruz saw reductions. “In our first six months, we saw a drop of 28 percent in burglary compared with the same locations and same time in the previous year,” he observes. They started knocking out “the low-hanging fruit,” he says. “If you catch one burglar, he can’t knock over a bunch of houses” later. Future reductions flow from already reduced numbers. And crime continued to drop. Burglaries fell by 7 percent, robberies by 27 percent. Arrests increased by 56 percent, while recovery of stolen cars increased by 22 percent.

Like Santa Cruz, other cities using PredPol have been getting promising results—an overall reduction in crime compared with other boxes in the city and in the same box a year ago. The results were immediate in Los Angeles. In the L.A. Foothill Division, in the four months following the start of the program in 2012, there was a drop of 13 percent, compared with an increase of 0.4 percent in the rest of the city. Between May 2012 and November 2012, during the LAPD pilot program, there was a 12 percent combined reduction in auto theft, burglary, and theft—the three crimes that L.A.’s PredPol tracks. Burglary alone saw a drop of 25 percent, compared with the same period in the same area a year earlier. In 2014, the Foothill Division saw a drop in auto theft, burglary, and theft from vehicles of 34 percent from the previous year’s lower figures. In the week ending February 15, 2014, Foothill cops spent 108 hours patrolling the hot boxes.

“The week ended with only 42 crimes in the whole division,” says Malinowski, who was captain of the Foothill Division at the time. “That’s in an area 50 square miles with a population of 250,000.” On Thursday of that week, February 13, the Foothill Division recorded no crime. Zero. “So,” Malinowski said, “something is working, right?” It is these striking results that the recent UCLA study captures and that led the LAPD to expand the program.

During roll call one evening, before Officers Allen and Bayer (their names have been changed for this article) had left the Los Angeles Foothill Division station house, they’d been given the daily printout of hot boxes in their precinct. In the watch commander’s office, a wall monitor displayed all the 500-by-500-foot boxes covering the entire division, with the hot boxes highlighted in red. Nearby, on the wall, eight videos showed live CCTV views of Van Nuys and some of the other main streets in the precinct—cars passing, an occasional pedestrian.

The two officers were not responding to a particular call—they were on “additional” patrol, covering predictive box M at Laurel Canyon and Mercer—one of the hot boxes in the 47.3 square miles of the Foothill Division. A mixed racial and economic community of 250,000 people, with some light industry, it consists of well-maintained one-story houses with porches and neatly kept front yards. Thirty gangs, many from other neighborhoods, show up at night. But the fight is gone. The gang members act more like the commuters they are. Fifteen to 20 years ago, the area saw frequent gang fights and shootings, stolen and torched cars, particularly around Hubert Humphrey Park (which, today, holds well-lit nighttime soccer games). Now, the area is safer. Kids who in previous eras may have been loitering on the corners tend to be inside more these days, playing video games.

In their patrol car, Allen and Bayer monitored their laptop, which connected them to the station house and various databases, including those containing car license-plate numbers and criminal records. As they drove through the Pacoima streets, they scanned the area for anything suspicious. “If I see someone walking in shadows instead of under streetlights, I might be suspicious,” said Sergeant Scott Kennedy, Foothill’s assistant watch commander. “At night, most people want to stay in the light.”

What else can make a cop suspicious? Someone holding his or her hand waist-level—possibly ready to pull a gun or drop a bag of dope. On a corner, guys glancing over one another’s shoulders as they talk, as if on the lookout; a car hugging the curb—someone who seems to be trolling, not going anywhere; and, of course, cars that match reports of stolen vehicles. Cops can follow bulletins on their onboard computers while responding to traditional calls from the precinct house.

At the hot box near Laurel and Mercer, Allen and Bayer spotted a car with five occupants—three females and two males, two of whom the cops recognized as gang members. Because the gang members had troubled histories, the cops called for backup from two officers working other hot boxes. When Allen and Bayer stopped the car, they found that one of the two guys in the backseat was carrying a loaded, snub-nosed .38 caliber pistol. A double-barrel 12-gauge shotgun lay on the rear floorboard. The male passenger copped to both weapons, and one of the female passengers was arrested for possession of a controlled substance. Back at the station, the officers checked in with officers from the Foothill Gangs Unit, who, it turns out, were looking for the gun suspect. The stop may lead to additional weapons charges and arrests.

“This was a great arrest,” Malinowski says, “a terrific example of being in the right place at the right time and of the seamless collaboration between detectives, patrol, and specialized units that we’ve got going here. We know from our experience that five gang members in a car with a pistol and a shotgun were probably going to end up in a shooting at some point, right? I don’t think I’m exaggerating when I say that we saved ourselves a shooting and a couple of victims.”

The police can make cities safe, but there is always a cost. Freedom or security: it’s a balance that we weigh every day. At what point does protecting society run the danger of infringing excessively on individual rights, or, more broadly, changing the nature of our democratic republic? And are there reasonable alternatives to these choices?

“Predictive policing has limited use,” argues Constance Rice, a civil rights activist, who cofounded and codirects the Advancement Project of Los Angeles. She finds the name “misleading. It’s not like they have a crystal ball, and they can predict where crime can be.” She’s skeptical that the time and resources devoted to predictive policing are worth it. She adds, “There can be civil liberties repercussions to anything the police do.”

“Predictive policing is not new,” says Richard Berk of the Wharton School at the University of Pennsylvania. “If you go back to the old TV shows—Dragnet—there’d be a map of the city, and there would be pins, and the pins would be concentrated in one area more than another. That’s been around since the 1950s.” According to Berk, predictive policing is just a fancier version of these efforts. It’s a quantitative, not a qualitative, difference—though in most fields, quantitative differences matter. “The additional feature is the mathematics, which helps interpret those pins on the map,” Berk admits, and he concedes that predictive policing may not just displace crime but reduce it. But he doubts “whether it’s as dramatic as some claim.”

There are “three potential problems with predictive policing,” according to Chris Calabrese of the American Civil Liberties Union. “First, garbage in, garbage out. If you put bad data in, you get bad results. By bad data, I mean historical inequities.” Calabrese focuses on stop-and-frisk, which he seems to equate with predictive policing, though most advocates of the latter are careful to distinguish between these approaches. The second problem, Calabrese said, “is transparency: how are these algorithms created, can you audit them, or are they a black box where the computer tells you where you focus, and there’s no accountability? Who is vetting the algorithm?” This concern may be more reasonable, since the brain of a computer is mysterious to most cops. The police must educate themselves about the algorithms used and demand clear explanations from those creating them. Perhaps citizen-review boards with appropriate expertise could help vet the algorithms. “Third,” says Calabrese, “what types of enforcement are being used?” Are the police looking at “where crimes were reported in the last few months, [or] are they looking on Facebook pages? Are they looking at friends of people who have been targeted on Facebook?” Would the ACLU be willing to work with PredPol? I ask. Calabrese hesitates: “Our work [is] to monitor civil rights.” But “our door is always open.”

“My fear is that these programs are creating an environment where the police can show up at anyone’s door at any time for any reason,” says Hanni Fakhoury, an Electronic Frontier Foundation lawyer. Fakhoury cites an incident in which the Chicago PD warned Robert McDaniel, 22, that he was on a “heat” list generated by an algorithm developed at the Illinois Institute of Technology to identify those most prone to violence and that the cops were watching him—though he had no violent criminal record.

“This is what civil rights activists are concerned about,” concedes the LAPD’s Malinowski. The worry is that police will create, as one headline suggested, a “real Minority Report computer to predict crimes,” referring to the dystopian film and its concept of “pre-crime,” in which individuals are arrested based on offenses that they supposedly would commit in the future. A number of predictive-policing software and analytics systems have been developed—IBM Modeler, Bair Analytics, and ESRI Mapping, among others—that do tend to focus on individuals. That could lead to constitutional or civil rights challenges in the future.

The PredPol police departments are different. None would generate a “heat” list such as the one used in Chicago. Again, PredPol focuses on geography—“place-based policing,” as Tacoma assistant police chief Peter Crimmins describes it. “The Constitution doesn’t go away,” adds Uchida. “We made a conscious decision that we weren’t going to target individuals. PredPol has stayed away from individuals and will continue to do that.”

To prevent the new era of Big Data from becoming authoritarian—to balance security with freedom—Bratton, who is sensitive to the danger, says that “it’s also important to make sure to have good people elected and appointed to office.” He continues: “The trust on which democracy itself rests is: you have standards of oversight and the ability to attract the right people into these positions of great trust. Isn’t that the whole foundation of what democracy is based on? We give up certain freedoms to other individuals, who have the power—as in the case of the police—to control your behavior. The challenge for the police is that it be done constitutionally. Legally. Respectfully. Compassionately. That it be done consistently. By consistently, I mean not policing differently in a poor neighborhood than in a rich neighborhood.”

The best defense against misuse of the police is citizen vigilance. When we give up our duties to police our neighbors to a professional force, we are not surrendering our responsibility to monitor those who act on our behalf.

It seems inevitable that some form of predictive policing is on the way. We can’t put the technology of policing back in the bottle any more than the Luddites could stop power looms. We’ll need to decide what forms the system should take—especially with the mounting danger to cities from terrorism. “As criminal and terrorist threats evolve,” Malinowski said a few days after the Paris and Mali terrorist attacks in November 2015, “law enforcement will need to continue to develop ways to use the vast amount of data available to analyze, measure, evaluate, and forecast risks in order to mitigate the impact of crime and terror events.”

Brantingham concurs. “Terrorist events will remain difficult to predict, as they are rare in a statistical sense,” he says, “but the convergence between crime and terrorism indicates that geographically based predictive policing that prevents crime by disrupting opportunities can also interfere with the freedom of action necessary in the planning of terrorist events. PredPol makes no assumptions about what specific environmental and social conditions drive crime or terrorism—and therefore, it is less subject to the biases that such assumptions can entail.”

The most optimistic scenario is that the technological revolution—through systems like PredPol—re-creates the best of traditional beat-cop policing. Officers will get to know their community and will, as in the PredPol model, incorporate community outreach. Police departments will do more with tighter budgets and fewer resources while also protecting individual rights. “For every 10 percent reduction of officers,” said Tacoma’s Yerxa, “there is a 5 percent increase in crime.” PredPol allows cops to reinvent Robert Peel’s preventive policing—to return to the humane principles of the 1830s with twenty-first-century tools. Bratton recently brought Malinowski to New York to consult on building a predictive-policing capability for the NYPD—and he envisions more interaction among the three great police departments in New York, L.A., and London. “We’re testing both PredPol and a new system, Hunchlab,” Bratton explains. “We haven’t committed to either. In the meantime, we have developed our own predictive model that we are field-testing against the other two.”

Now 68, with nearly a half-century in law enforcement behind him, Bratton remains as committed as ever. “It’s my heart, soul, and passion,” he says. “The importance of policing. No one can do it better than us, but we can’t do it alone.”

Night. The L.A. Foothill Division patrol car passed IncoTech Aerospace Fasteners, near what used to be gang turf, along Van Nuys Boulevard, past Rosie’s Tax and Plus. San Fernando Road—past Chabelita’s Restaurant, not far from where dealers used to peddle heroin. Best Buy, Costco, Lowe’s, a Subway, a Panda Express. Hillery T. Broadous Elementary School. One-story ranch houses, beach chairs on porches, front doors flanked by lights. Walls that used to be tagged up that are now free of graffiti. A few stables. Not long ago, someone was arrested for sex with a horse.

On his patrol-car computer, Sergeant Scott Kennedy, the Foothill Division assistant watch commander, punched in a code, letting the precinct know that he was entering a hot box. Kennedy slowed as he skirted Ritchie Valens Park. Hubert Humphrey Memorial Park: under banks of lights, kids played a soccer game. Paxton Park. Near the intersection of two freeways—210 and 118—Kennedy stopped and got out.

When Kennedy first joined the department, kids would push cars into the dry channel and set them on fire. Gangs fought over turf. There were muggings, murders. Thirty years ago, in most cities, when a cop came around the block, people alerted one another by whistling—just as at the beginning of West Side Story. Now, at night, you may see a twinkling of light spreading outward as people hit their cell phones to alert friends.

Kennedy walked into a tunnel, an underpass, still covered with graffiti. As long as one gang didn’t spray over or cross out another gang’s tag, everything was cool. The tunnel smelled damp. An empty beer bottle. A used condom. At the end, Kennedy stopped, looked around. At the tunnel’s entrance, backlit, a shadow flicked past and then returned, joined by three other shadows and then two more. Six, seven bodies blocked the way back to his patrol car. Kennedy kept his eyes on the shadows at the end of the tunnel as he approached them. He stood up straighter. His right hand drifted down toward his holstered gun. But—except for that slight body adjustment—he made a point of being open, affable, as he greeted the people at the end of the tunnel.

“How’s it going? Nice night, huh? Everything okay?” Any tension was defused. The group dispersed. Kennedy returned to his patrol car.

Back at the Foothill station house, Malinowski asked me how the night went.

“Boring,” I said. “Nothing happened.”

“Yeah,” Malinowski grinned. “That’s the story.”

Top Photo: Ann Hermes/The Christian Science Monitor/AP Photo

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