Marvin D. Krohn is a Professor in the Department of Sociology and Criminology & Law at the University of Florida, Gainsville, USA. He is primarily interested in developmental and life-course approaches to the explanation of delinquency, drug use, and crime. He is a Fellow of the American Society of Criminology.

James C. Howell is a Senior Research Associate with the National Gang Center, Tallahassee, USA. He is author of The History of Street Gangs in the United States (2015), and a textbook, Gangs in America's Communities (2019). His numerous other works on youth gangs include a developmental theory of gang involvement.