From the streets of Chicago and Los Angeles, to indictments this month targeting criminal networks in Savannah, Georgia and white supremacists in Grand Prairie, Texas, tens of thousands of gangs are responsible for drug crimes, brutal killings and other forms of violence.

According to one recent estimate, nearly one-and-a-half million people are members of gangs in the United States.

In this episode, we look at the lessons learned from the successful police and federal crackdown against Sex Money Murder (SMM), New York City's most violent drug gang in the early 1990's. The Bronx had one the highest murder rates in the country. The notorious SMM was the most violent gang in the city.

Our guest, Jonathan Green, is the author of the new book, "Sex Money Murder: A Story of Crack, Blood and Betrayal." He tells the hair-raising story of how SMM brutally dealt with rivals and anyone else who got in their way, as well as the economics of the crack epidemic, which brought great wealth to gang leaders.

This episode looks at the work of Detective John O'Malley, housing cop Pete Forcelli. federal prosecutor Liz Glazer and others who risked their lives to take violent crews off the streets and win convictions against SMM'S leading members. Jonathan also tells the story of gang leader "Pistol" Pete Rollock and two his top lieutenants, Suge and Pipe.

We look at what works today in the fight against gangs, including the use of federal RICO laws, and intervention by local communities.