And yet, while earlier examples of victim-focused advocacy in Latin America have been aimed mainly at governments, many of Mexico’s so-called victim visualizers say they are less interested in politics and marches than in changing their neighbors’ mind-sets. Their campaigns are mostly attempts to create a public conscience, to keep people from committing or accepting violence by making them feel the suffering that ripples out from crime — largely through efforts that can be shared easily by word of mouth or social media.

“These movements are significantly different from the good old ‘marchas,’ ” said Andrés Monroy-Hernández, a fellow at Harvard’s Berkman Center for Internet and Society. “The stereotype of the marchas was that they were movements made up of working-class folk, led by charismatic union or political leaders. These new social media movements seem to be structurally different: they are networked, and attract a different demographic — middle-class youth who probably identify more strongly with Occupy Wall Street and the Arab Spring.”

The Ecatepec project was actually inspired by a star of both the street and the Web: the French photographer known as JR, who posts huge portraits on buildings and in public spaces. A few years ago, he displayed poster-size photos of young people from the housing projects around Paris. Later, in the Middle East, he hung portraits of Palestinians and Israelis side by side, on both sides of the walls that divided them. (Last year, JR won an annual $100,000 prize from TED, the tech-savvy conference juggernaut concerned with “ideas worth spreading.”)

The process in Mexico was more communal. The Murrieta Foundation gave photography classes to young people from rough neighborhoods and recruited crime victims as their subjects.

“Victim” was defined broadly. Along with those who had witnessed murders firsthand, lost relatives or been the victims of violent crime, the category included drug addicts, the girlfriends of criminals and an old man who feared that he would never see his imprisoned son before he died. The subjects’ stories were put together in a compilation of testimonials, their names withheld for security reasons.