Violence in Chicago neighborhoods. A number of NIJ studies have considered why some youth become violent and use guns. Researchers analyzing data from a long-term study in Chicago showed that young people who witness gun violence are more likely to engage in violent crime. Youth who live in dangerous, disadvantaged neighborhoods and have been exposed to violence are more likely to carry guns.
Read more about this study in Adolescents, Neighborhoods, and Violence: Recent Findings From the Project on Human Development in Chicago Neighborhoods (pdf, 24 pages).
Differential association — why a particular person comes to engage in criminal behavior. The theory of "differential association" was first introduced in 1934 by Edwin H. Sutherland to explain the "process by which a particular person comes to engage in criminal behavior." The process is described in nine points that basically state that criminal behavior is learned through interaction with other persons, specifically within "intimate personal groups," where the person learns techniques of committing crime and the "specific direction of motives, drives, rationalizations, and attitudes."
Read an abstract about this book, Principles of Criminology.
A long-term study — Co-Offending and Patterns of Juvenile Crime — using data from Philadelphia police records confirmed the "differential association" theory of delinquency. The study showed that:
Violence appears to be learned in the company of others. Those who commit crimes with violent offenders, even if the group does not commit violent crimes, are likely to subsequently commit violent crimes. This suggests that young offenders pick up attitudes and values from their companions.
Construct Theory. The above study was in part based upon J. McCord's "Construct Theory," which holds that:
[D]elinquents learn to classify criminal actions as appropriate partially through finding that others think it normal to commit crimes. It follows that juveniles would be more likely to consider violent behavior to be appropriate when committing crimes if their companions consider violence appropriate.
The authors advocate against interventions that place youths "in groups that unintentionally provide negative peer learning."
Read more about Construct Theory in Co-Offending and Patterns of Juvenile Crime.
How youth get guns. Researchers in Atlanta asked incarcerated youth how and why they obtained and used guns. Almost all said that they could easily obtain a gun, would most likely obtain guns illegally on the street, and that gun carrying was commonplace:
[They] had strong feelings about carrying guns — 29 percent of males and 75 percent of females said they did it to feel safer (for protection), and approximately 40 percent overall said it conferred status and made them feel more "energized" and "powerful."
Read more about this study in Reducing Gun Violence: Community Problem Solving in Atlanta (pdf, 40 pages).
This was consistent with earlier findings from surveys conducted in Boston and nationally.
Learn more about gun surveys from Who Has Illegal Guns and How Are They Acquired? and Gun Ownership Surveys.