This case captures what is wrong with our “justice” system: We have invested in mass incarceration in ways that are crushingly expensive, break up families and are often simply cruel. With less than 5 percent of the world’s population, the United States has almost one-quarter of the world’s prisoners.

This hasn’t always been the case, but it is the result of policies such as mandatory minimum sentences since the 1970s.

In 1978, the United States had 307,000 inmates in state and federal prisons. That soared to a peak of more than 1.6 million in 2009. Since then, the number of inmates has declined for three consecutive years to 1.57 million in 2012. The number of juveniles detained has also begun to drop since peaking in 2000, although the U.S. still detains children at a rate five times that of the next highest country.

In short, there’s some hope that this American experiment in mass incarceration has been recognized as a failure and will be gradually unwound. Among the leaders in moving away from the old policies are blue states and red states alike, including New York and Texas. But America still has twice as many prisoners today as under President Ronald Reagan.

Almost everyone seems to acknowledge that locking up vast numbers of nonviolent offenders is a waste of money. California devotes $179,400 to keep a juvenile in detention for a year, and spends less than $10,000 per student in its schools.

Granted, mass incarceration may have been one factor in reduced crime in the last couple of decades; there’s mixed evidence. But, if so, the economic and social cost has been enormous — including the breakup of families and the increased risk that children of those families will become criminals a generation later.