In more than 40 years of studying this city's street gangs as a social psychologist, Malcolm Klein says his home was burglarized nine times. Now, the retired University of Southern California professor is offering the city what he hopes one day will help stem crime: A test that he says could predict if a child is destined to join a gang.

The multiple-choice screening, some 70 questions long, shows how closely Los Angeles has begun to examine the work of social scientists to tackle complex policy issues like gang violence. Last year, city officials turned to Klein and his colleagues at USC to design a test that they hope will empirically identify which children are headed toward a life on the street. This year, the test will help decide the direction of the millions of dollars the city spends annually on gang-prevention efforts.

The screening, intended for children between 10 and 15 years old, asks a range of questions on issues ranging from past relationships to drug use to attitudes toward violence. One question asks test takers if they recently had a breakup with a boyfriend or girlfriend; another asks test takers if they are kind to younger children.

In order to avoid stigmatizing children with the label of potential criminal, Klein says test takers aren't told that the questions are intended to screen for future gang involvement.

Some youth advocates are worried the test will identify too few children who could genuinely benefit from gang-prevention programs. "This cannot be the only solution," says Ellen Pais, a senior director at Urban Education Partnership, a Los Angeles program that hosts events such as community plays to provide alternatives to gang activity. "We didn't expect this to be so narrow."

Recent research is challenging many of the city's ingrained practices for gang prevention, Klein says. For example, programs to rehabilitate gang members by assigning them to group community-service projects actually reinforce their identities as delinquents. And Los Angeles's strategy of suppressing gangs by barring members from gathering in public places ends up deepening their ties to the group, he says.

Previously, city officials depended on what they concede was a patchwork of information to build gang-prevention programs, often using anecdotal tips from local beat cops or high school teachers. "We were not relying on data," says Rev. Jeff Carr, an evangelical minister who is the city's "gang czar," leading outreach and prevention efforts. "We had gang-prevention programs, but no criteria to determine who was in a gang."

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