Gerald Rich Andy Rossback Ivar Vong Interactive byand Justice Lab is a column that examines the science, social science and technology of criminal justice

A growing number of criminal justice reform organizations, among them the ACLU, Rebuild the Dream, and Just Leadership USA, are uniting behind one big goal: to reduce the prison population by 50 percent within the next 10 to 15 years.

With 2.3 million Americans incarcerated in prisons and jails, a 50 percent reduction would mean changing sentencing and parole rules to cut the net population by more than 1 million people, either by releasing current inmates or by not incarcerating future offenders.

Left mostly unsaid is that achieving the goal of this “Cut50” movement would entail touching what has long been a third-rail in criminal justice reform. To halve the prison population, sentencing would have to change not only for the so-called “non, non, nons” — non-violent, non-serious, and non-sex offender criminals — but also for some offenders convicted of violent crimes.

These changes could include shortening sentence lengths; making it easier for prisoners to win parole; deciding that probation or community service are more appropriate consequences than prison time for entire classes of crimes; diverting more suspects to mental illness programs or addiction treatment; and even redefining what offenses are considered violent in the first place.

Simple math shows why violent offenders would have to be part of any serious attempt to halve the number of prisoners. Consider the nation’s largest incarcerated population, the 1,315,000 held in state prisons. Only 4 percent are there for drug possession. An additional 12 percent are incarcerated for drug sales, manufacturing, or trafficking. Eleven percent are there for public order offenses such as prostitution or drunk driving, and 19 percent for property crimes such as fraud and car theft, including some property crimes that many consider serious or violent, such as home invasion.

That leaves a full 54 percent of state prisoners who are incarcerated for violent crimes, including murder, kidnapping, manslaughter, rape, sexual assault, and armed robbery.

So if 100 percent of all people convicted of drug, public order, and property crimes were released early or sentenced to punishments other than prison time, you would still need to free, say, 30 percent of robbery offenders to achieve a 50 percent reduction in the prison population.

Interactive How would you Cut 50? In In scenario one , all property, drug, public order, and "other" offenders would avoid state prison time or be released early, in addition to 30 percent of those convicted of robbery. In scenario two , half of robbery and assault offenders would be released or never incarcerated, in addition to 3 percent of sex offenders, three-quarters of property and drug offenders and 100 percent of public order and "other"offenders.

Though there is a strong bipartisan movement for sentencing reform, discomfort with allowing violent criminals to avoid prison time or to serve much shorter sentences has left prominent conservatives reluctant to echo the call to “Cut50.”

"I have long argued that our criminal justice system locks up too many people for too long,” former House Speaker Newt Gingrich told The Marshall Project in an email. “I have also argued that we should maintain harsh punishments for violent or hardened criminals.”

Pat Nolan, a leading conservative prison reformer dating back to his own 25-month federal sentence for racketeering, said, “I’m not comfortable saying, ‘Yes, 50 percent would be the right number.’ I’m more comfortable saying that we need to dramatically cut the number of people in prison and find that sweet spot where we are protecting the public but not wasting expensive beds.”

Vikrant Reddy, coordinator of the Right on Crime campaign, agreed. “The focus among conservatives is the low-level nonviolent offenders.” As for Cut50, “I just don’t like the name of this organization. The reason is because I see this issue, and most conservatives see this issue, in terms of public safety. If I felt confident the levels of incarceration we have in the United States made us a safer society, I would begrudgingly say, ‘So be it.’”

“I really admire what Cut50 is trying to do, but I am concerned that people are going to misunderstand it,” Reddy added. “The bottom line is not just getting the levels of incarceration down. The end point is that crime rates are still too high.” (Crime is currently at a four-decade low, although rates remain high in segregated, high-poverty neighborhoods.)

Civil rights activist Van Jones is co-founder of Rebuild the Dream, the organization promoting the “Cut50” tagline. Jones and Gingrich are co-hosting a March 26 conference in Washington, D.C. to bring criminal justice reformers together across party lines. Jones acknowledges that conservatives have not signed onto the Cut50 goal. But he points out that many people convicted of violent crimes have, in fact, not hurt anyone physically, such as offenders picked up for theft or burglary and discovered to have a gun on them.

“We might want to look at whether someone who had a gun but didn’t use it should be considered violent,” Jones said. “People will say that’s gun crime and you can’t talk about them. Well, I think that’s ridiculous.”

That might discomfit some liberals who favor stricter gun controls. Meanwhile, the idea of the home as a castle has been popular on the right, resulting in laws that rank burglary alongside violent bodily assault. So on both sides of the political spectrum there is lingering support for the tough sentences that would have to be reduced in order to cut the prison population by 50 percent.

Jones and other reformers, both progressive and conservative, say it is not yet time to focus on the hot-button question of whether to redefine violent crime. “We’re not heavily leaning into that part of the conversation yet, because there is so much common ground on the nonviolent offenders, the indigent population, and the mental health population. We think we can get some momentum going,” Jones said.

Meanwhile, some scholars point out just how modest — by international and historic standards — a 50 percent reduction in the prison population would be.

“When does mass incarceration become regular incarceration?” asked Michael Jacobson, a former New York City corrections and probation commissioner and director of the CUNY Institute for State and Local Governance. To bring the United States to a prison incarceration rate equal to that of European nations — or to our own rate in the early 1970s — we would have to slash our incarceration rate from 623 per every 100,000 adults to about 150 per 100,000. That would be a reduction of approximately 80 percent.

And that would entail some very new thinking. In Europe, a murder sentence of 10 years is considered severe, according to University of Pennsylvania political scientist Marie Gottshalk, whereas life without parole is almost the norm in the United States. Then there is one of the fastest growing groups of American prisoners — those convicted of sex crimes. “A sex offense can be flashing, or raping and murdering a child,” Gottschalk said. “We’re having a quiet war on sex offenders now, and very few people are saying we have to stop that war.”

Those who support Cut50 point out that removing low-level offenders from prison would also naturally lower the violent population, too. Because conditions behind bars are so harsh, incarceration has an acknowledged “criminogenic” effect, turning novice offenders into career criminals and increasing recidivism. (Social science suggests the experience of being incarcerated increases the likelihood of recidivism only modestly, by 5 to 9 percent.)

Jones argues that despite the political challenge in getting to a 50 percent reduction, there are reasons to be optimistic. States have cut the juvenile incarceration rate in half since the mid-1990s without an increase in youth crime. “That should give us a lot of encouragement,” he said. “Numbers that when you first say them sound shocking and impossible are actually doable.”

Alison Holcomb, director of the ACLU campaign to end mass incarceration, said, “We’ve committed to a 50 percent reduction, and more than anything, that’s to force the question of, ‘Well, why not?’” Holcomb’s father-in-law was murdered during an armed robbery, so she understands intimately the sensitivity of speaking about shorter sentences for violent crimes. “There’s quite a range,” she said. “The spouse who plots a murder and hires someone to kill their partner, versus, in my husband’s father’s case, the 17-year old committing an armed robbery and creating a great risk. He pulls the trigger and kills somebody.”

“I think we are capable of identifying those shades of grey within even violent offenses,” Holcomb said. “The tricky part is how you fashion laws based on the nuances of humanity.”

And that will require a shift in public attitudes toward crime and punishment. Polls do show support for lowering the prison population, but the surveys typically frame such reductions as a way to rehabilitate low-level offenders while “keeping violent criminals in prison for their full sentences.”

Glenn Martin, founder of Just Leadership USA, believes the public will only embrace the Cut50 movement if inmates and their families are humanized. “What’s the public really scared of? If it’s only crime, we could get out of this mess quickly. This is about race, this is about class, and we have to tackle those issues. The way you do that is by changing the way the public thinks about who is or was in prison.”

That includes people like Martin himself, who served a six-year sentence for robbery. “It’s a moral argument, that historically, leads to reform,” he said. “You think of HIV/AIDS. It’s not until the people impacted spoke directly to the public that you started seeing real change.”