An inmate looks down from his cell in D.C. Central Jail. (J. Lawler Duggan/For The Washington Post)

Among the many shameful legacies of racial discrimination and segregation in the United States is the fact that African Americans make up a disproportionate share of both those who are victims of violent crimes and those who are incarcerated for committing them.

“Locking Up Our Own,” a remarkable new book by Yale Law School professor and former D.C. public defender James Forman Jr., tells the poignant but neglected story of how newly enfranchised black communities coped with this dilemma as a crime wave swept through urban America in the 1980s and 1990s, driving the murder victimization rate among blacks to an astonishing high of 39.4 per 100,000 population in 1991.

African American mayors, police and prosecutors responded to the pleas of beleaguered constituents with rhetoric, and policy, that were no less “tough on crime” than that of their white counterparts. Black leaders often framed crime-fighting as an issue of salvaging the civil rights revolution.

“What would Dr. King say?” about the violence plaguing predominantly black cities, they would ask rhetorically — and then crack down on mostly youthful offenders, which inevitably involved “locking up our own.”

This was an era, Forman reminds us, during which activist-attorney Johnnie Cochran regularly attended rallies against drug dealing in Los Angeles, calling for PCP dealers to be punished “harshly,” and Eric Holder, then the District’s top prosecutor, supported aggressive, often pretextual police stops and searches of cars in predominantly black sections of the city, in a desperate effort to get guns off the street.

Forman’s beautifully written narrative, enriched by firsthand knowledge of the cops and courts, neither condemns black leaders in hindsight nor exonerates the white-dominated institutions that laid the basis for what dramatic block letters on the cover of an August 1979 “special issue” of Ebony labeled “black on black crime.”

However, he adds historical nuance to the story of “mass incarceration” told in Ohio State University law professor Michelle Alexander’s influential 2010 book “The New Jim Crow.”

This makes Forman’s book the second important corrective this year to Alexander’s. The first, “Locked In” by Fordham University law professor John Pfaff, deployed statistical evidence to show that the United States’ highest-in-the-industrialized world incarceration rate did not result from the war on drugs, contrary to a theme of Alexander’s book that has been repeated so often Pfaff dubs it “the Standard Story.”

Even if everyone in state and federal prison on a drug conviction were released tomorrow, the U.S. incarceration rate would still be about quadruple what it was in 1970. That is because, Pfaff demonstrates, most people in prison are there for violent crimes such as homicide or aggravated assault.

Punishment for these offenses drove incarceration rates higher, Pfaff shows, but not, as is often supposed, because of laws imposing harsh mandatory- minimum sentences.

The key factor was discretionary prosecutorial decisions; at least from the early 1990s on, prosecutors in the nation’s 3,000-plus counties charged arrestees with felonies at a higher rate even as the crime rate itself declined. Ultimately, more punitive exercise of prosecutorial discretion fed a steady net influx of convicts to state prisons.

District attorneys were motivated by tough-on-crime politics and enabled by cost-shifting economics: Counties pay for police and prosecution, but imprisonment comes out of the state budget.

The most recent evidence indicates that the age of mass incarceration is abating; it has been, oddly enough, since just prior to the publication of “The New Jim Crow.”

The Pew Charitable Trusts has reported, based on Justice Department data, that the U.S. incarceration rate declined from a peak of 1 in 100 adults in 2007 to 1 in 115 in 2015. Keith Humphreys, of Stanford University, has shown that racial disparities, though still large, may be diminishing. The incarceration rate for blacks fell steadily between 2000 and 2014, while that of whites rose slightly.

The challenge now is to accelerate the de-incarceration trend while sustaining low levels of crime. A troubling uptick in urban homicide last year may have helped elect President Donald “American Carnage” Trump. Certainly his harshest, most racially tinged anti-crime rhetoric both stimulated fear and exploited it. His attorney general, Jeff Sessions, has called for punishing crime rather than consent decrees against allegedly abusive local police.

Under the circumstances, Forman and Pfaff’s emphasis on local politics, and county- and state-level prosecutorial discretion, is paradoxically hopeful.

Federal policy makes headlines, but in the vast majority of cases, criminal justice takes place at the grass roots. And in recent years, that is the level at which the most promising reform efforts have occurred. Those efforts can and should continue, whatever might happen next in Washington.

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