The continued narrative emanating from the prison and capital punishment abolition movements (marking this recent article from the Los Angeles Times) is that three-strikes legislation fills prisons and bad social conditions cause crime.
The first is true—and has resulted in crime rates dropping—but the second is not and continues to hamper rehabilitative efforts by diverting focus on the true cause of crime, that criminals choose to become criminals.
Granted, there are certain social, familial, psychological and physiological conditions from which many criminals tend to come, though many within the same conditions do not choose to become criminals, so we are left with the one indisputable fact, crime is a matter of individual choice.
The best work in the arena of crime causation over the past several decades has been that done by James Q. Wilson and his collaborators, expressed magisterially in his two major works, as the co-author of Crime & Human Nature (1985) & as co-editor of Crime & Public Policy (2011).