Massachusetts Court Chips Away at Third-Party Doctrine


Police Accept Gag Rules on New Surveillance Tech

Criminal Justice

Police Struggle to Act Effectively on Social Mapping Data

In the 19 years since New York’s police department pioneered the CompStat crime mapping system, using computerized maps of crime activity to target law enforcement has become a best practice for major U.S. police departments. (The approach has also spread to other municipal services, helping officials identify systematic problems with garbage collection, for example.) But what happens when computers begin flagging people, rather than city blocks, as “high risk”?

In Chicago, a DOJ-funded pilot program is now predicting which residents have the greatest chance of being involved in a homicide (whether as perpetrator or victim). The programs maps social ties among neighborhood residents using internal police department records and (through a second, related targeting effort) school attendance records and other educational data. As Chicago Magazine recently explained, even “within [a] high-crime, high-risk neighborhood, there are very different levels of risk.” For example, within one African-American community, a network of “co-offenders” (people arrested together for the same crime) comprised just 4% of the population but suffered almost 40% of the homicides. The links among the group can be represented visually:


But police have not yet figured out how to use this information effectively.

The March issue of Harper’s magazine describes the story of Davonte Flennoy — a young black man in Chicago, flagged as ultra-high risk by the system, who was placed in a resource-intensive daily mentoring program, but nonetheless was killed in a gang shooting. Other interventions have included sending police captains to knock on the doors of those who appear on the computer’s “heat list” of high risk residents.

As Andrew Papachristos, a Yale sociologist helping lead the Chicago project, explained, “When you look at a geographic map and it says, ‘Here’s a hot spot on the corner of 63rd and Knox,’ you know what to do . . But when you say, ‘This is a group of people who are in a really high-risk social network,’ it’s not clear exactly how to interpret that for policing.”

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