The United States of America keeps more of its citizens under lock and key than any other country on earth. This is not a good thing. But is it a necessary one?

Five years ago Michelle Alexander energized a new discussion of American prisons in her book “The New Jim Crow.” So many black men are locked up, mainly for nonviolent drug offenses, in her view, as to present a home-grown human rights emergency. That viewpoint now dominates elite opinion, so much so that many fine minds and humane sensibilities on the right and the left are coming to grips with putting an end to “mass incarceration.”

Professor Alexander’s ideas are hardly new ones. I can remember when Kurt Schmoke, then state’s attorney for Baltimore City, was describing Maryland’s prisons as “like South African homelands” in the apartheid era more than 30 years ago. An older generation feels vindicated, and a new generation is listening.

Most of the men I met in prison as a correctional case management specialist were African-American. Each of them had a unique story, but I got more than my fill of their tragedies. So many of them were young and had embarked on what we called “doing life on the installment plan.” Drug abuse and drug-selling certainly were all too often part of the countless criminal careers I studied. But many of these men had thrown their lives away on hideous violent crimes, which brings us to the heart of the matter: How do we protect ourselves from men and women who have given way to violence without locking them up?

First, let’s dispense with the notion that it is mainly drug convictions that are filling up our prisons. Fordham Law School Professor John F. Pfaff, a master numbers cruncher and no fan of prisons, has published a new book called “Locked In: The True Causes of Mass Incarceration and How to Achieve Real Reform.”

He writes: “Over half of all state inmates are in prison for violent crimes, and the incarceration of people who have been convicted of violent offenses explains almost two-thirds of the growth in prison populations since 1990. Similarly, almost all the people who actually serve long sentences have been convicted of serious violent crimes. To make significant cuts to state prisons, states need to be willing to move past reforms aimed at the minor offender and focus much more on the (far more politically tricky) people convicted of violent offenses.”

In another new book very much along the same lines, “Locking Up Our Own,” Yale Law School Professor James Forman Jr. writes, “Roughly 20 percent of America’s prisoners are in prison on drug charges. As a result, even if we decided today to unlock the prison door of every single American behind bars on a drug offense, tomorrow morning we’d wake up to a country that still had the world’s largest prison population.”

I have seen too many lives blighted by very bad choices not to wish with all my heart that we could do without so many prisons. To that end, I am in favor of doubling (at least) the budgets of public defenders; of expanding prison industries and work training for inmates (long opposed by chambers of commerce and labor unions, by the way); a vast expansion of drug treatment options, in and out of prison; of expunging arrest records not leading to conviction and even some minor convictions; of as many services for released convicts as we can provide; and of repealing the Second Amendment, so as to tailor gun regulation to wherever the need is, at national, state and local levels.

But we must not avert our eyes from present emergency. As of Monday, Baltimore has already suffered 160 homicides this year. Shootings, carjackings and robberies are also spiking here (the victims of which, by far, are African-American). So I do not see much hope of reducing “mass incarceration” in the United States. Until someone else comes up with a better idea, the containment of violent crime depends on taking dangerous people off the street.

Hal Riedl retired from the Maryland Division of Correction in 2010 and from the office of the state's attorney for Baltimore City in December 2014. His email is haroldriedl@gmail.com.