• Social Network Analysis

    Social network analysis is a mathematical method to describe the structures of street groups. It is increasingly helpful in identifying high-risk individuals to engage with community-based interventions.

About the Innovation

One tool researchers have used to identify high-risk group members is social network analysis (SNA). Yale sociologist Andrew Papachristos has developed a mathematical method to identify the structures of street groups using connections contained within police records of arrests, field stops, and similar data. SNA recognizes that the overwhelming majority of suspects and victims in homicides and shootings know one another. In fact, Papachristos has demonstrated that they are often part of a closely linked social network — that is, shooters and victims tend to be closely linked to many other shooters and victims.

Research on these social networks has found that individuals with links to street groups and those closely linked to homicide victims are at elevated risk of becoming shooters or victims themselves. SNA has helped communities identify group members to notify. Using co-arrest and field stop records, SNA can create graphs of connections between street group members. A GVI partnership can use these maps to identify “brokers” — people with a profusion of group-related connections — and people closely connected to homicide victims and suspects. These high-risk group members can then be given custom notifications to give the city’s antiviolence message the greatest reach and to disrupt street group networks.


We live in a "connected world," not metaphorically, but literally. The ways in which people, groups, organizations, and institutions are connected to each other affects what we feel, think, and do. The growing field of network science has been used to understand a wide range of behavior from the people we marry and the votes we cast to the diseases we catch and the spread of information. This workshop, instructed by Andrew Papachristos of Yale University, is designed to give criminal justice and violence prevention practitioners a basic understanding and working knowledge of social network analysis and, specifically, how it applies to understanding gun violence in U.S. cities. The workshop will contain several “hands on” and interactive models that will walk attendees through the basic computer, data, and analytic skills needed to integrate network analysis into their programmatic efforts.


  • This training is part of a project supported by a Cooperative Agreement (Number 2012-CK-WXK039) awarded to Yale University by the Office of Community Oriented Policing Services, U.S. Department of Justice.  Additional support to support trainees’ travel was funded through the Bureau of Justice Assistance, Office of Justice Programs, U.S. Department of Justice (Grant. 2013-DG-BX-K021).  The opinions contained herein are those of the author(s) and do not necessarily represent the official position or policies of the U.S. Department of Justice. References to specific agencies, companies, products, or services should not be considered an endorsement by the author(s) or the U.S. Department of Justice. Rather, the references are illustrations to supplement discussion of the issues.
  • Workshop materials were developed, in part,  with support from the Bureau of Justice Assistance, U.S. Department of Justice, to the National Network for Safe Communitiesat John Jay College of Criminal Justice.
  • A CAREER award (SES-1151449) from the  Sociology, and Law and Social Science Programs at the National Science Foundation helped funded a large portion of the research highlighted in this workshop.

News & Updates

How Violence Cascades Through Chicago

May 2017  |  Chicago Magazine  

Yale sociologist (and NNSC partner) Andrew Papachristos has conducted extensive research about the social-network theory of gun violence. In Papachristos' latest paper, he and his co-authors consider the timing of homicide victimization within these social networks. In other words, if one person is killed, how much time passes between his death and the next homicide among people he "infected"?

Tags: Chicago Social Network Analysis Social Network Analysis

I Just Lost My Fourth Student This Year to Gun Violence. I Want to Make Sure He’s the Last.

April 2017  |  The Trace  

Tammatha Woodhouse, principal of Excel Academy in Baltimore: "I gave teachers an article by [Yale professor Andrew Papachristos]. It’s about treating gun violence as an epidemic, the way we do with HIV. I felt that the important takeaway for my kids was the idea that bad behavior of people in your social network – your friends and neighbors and relatives – can place you at high risk if you’re interacting with them on a daily basis. Some of the students could relate to the idea of changing your friends. Like, “If I don’t smoke marijuana, why am I hanging out with folks who smoke it?”

Tags: Baltimore Social Network Analysis Social Network Analysis

Researchers Begin To Look At Gun Violence As Public Health Issue

January 2017  |  NPR  

National Network partner Andrew Papachristos and his colleague Gary Slutkin "have started to look at gun violence as a public health epidemic, and how to take a holistic approach and reinterpret the problem."

Tags: Social Network Analysis Social Network Analysis

Race And Policing: Treat Black Men And Boys Like Victims, Too

October 2016  |  NPR  

When researchers looked "at gun violence the way epidemiologists study disease — examining the way it spread by social connections. And like a virus, they found that there were certain people who were especially at risk of being touched by it."

Tags: Social Network Analysis Social Network Analysis

In Effort To Curb Violence In Chicago, A Professor Mines Social Media

September 2016  |  NPR  

"[Professor] Patton [of Columbia University] is trying to create an algorithm that will monitor and identify who might be the next victim or shooter."

Tags: Social Network Analysis Social Network Analysis

CPD’s crucial choice: Treat its list as offenders or as potential victims?

July 2016  |  Chicago Tribune  

NNSC research partner Andrew Papachristos penned a recent op-ed to discuss the methodology and motivation behind Chicago's Strategic Subject List. 

Tags: Chicago Custom NotificationsSocial Network Analysis Custom NotificationsSocial Network Analysis

Gangs tied to 49 percent of shootings in New York City, mostly over petty disputes

December 2015  |  New York Daily News  

"Along with the mass killers and rifle-toting terrorists who are driving the nation’s gun debate are New York’s own gangbangers, who are behind the triggers of nearly half the city’s shootings, officials said. And when gunplay across the five boroughs turns deadly, gang members are quite often responsible, accounting for 130, or 40%, of the city’s murders this year, police said."

Nicolas Enriquez

Tags: New York City Social Network Analysis Social Network Analysis

Use of Data Can Stop Crime by Helping Potential Victims

November 2015  |  New York Times  

Andrew Papachristos is a professor at Yale University and a Senior Research Advisor for the National Network. He recently published this article as part of a New York Times' series asking: "Can Crime be Ethically Predicted?" Professor Papachristos offers a nuanced view of how data can be used in crime prevention. 

Tags: Social Network Analysis Social Network Analysis

Rockford police to map city’s social crime networks

October 2015  |  Rockfrod Register Star  

" Police plan to analyze criminal social networks in an attempt to reveal who is most likely to be involved in violent crime, either as an offender or as a victim."

Tags: Rockford Social Network Analysis Social Network Analysis