William Thomas, a retired Newark police sergeant, left his home in a body bag. To his dismay, he was still very much alive. A team of cops and medical technicians had strapped his limbs together, stuffing his body into a mesh sack to restrain him after he tried to fight them off.

Six hours earlier, Thomas, a decorated narcotics investigator and a veteran of the New Jersey Air National Guard, tortured by post-traumatic stress disorder acquired in Iraq, had downed a fistfull of prescription sleeping pills with an entire bottle of Bermuda rum. He collapsed onto his stepson’s bed, calmly waiting to die. This was the second time since returning from war and rejoining the police force that he had tried to take his own life.

The debate over the militarization of America’s police has focused on the accumulation of war-grade vehicles and artillery and the spread of paramilitary SWAT teams. What has gone largely unstudied, however, is the impact of military veterans migrating into law enforcement. Even as departments around the country have attempted a cultural transformation from “warriors” to “guardians,” one in five police officers is literally a warrior, returned from Afghanistan, Iraq or other assignments.

The majority of veterans return home and reintegrate with few problems, and most police leaders value having them on the force. They bring with them skills and discipline that are regarded as assets. But a Marshall Project investigation indicates that the prevalence of military veterans can also complicate relations between police and the communities they are meant to serve.

To the obvious question — are veterans quicker to resort to force in policing situations? — there is no conclusive answer. Our investigation obtained data from two major-city law enforcement agencies, and considerable anecdotal evidence, suggesting veterans are more likely to get physical, and some police executives agree.

But any large-scale comparison of the use of force by vets and non-vets is hampered by a chronic lack of reliable official record-keeping on issues of police violence.

Some other conclusions about veteran-cops emerged more clearly:

Veterans who work as police are more vulnerable to self-destructive behavior — alcohol abuse, drugs and, like William Thomas, attempted suicide.

Most law enforcement agencies, because of factors including a culture of machismo and a number of legal restraints, do little or no mental health screening for cops who return from military deployment, and provide little in the way of treatment.

Hiring preferences for former service members that tend to benefit whites disproportionately make it harder to build police forces that resemble and understand diverse communities.

When William Thomas returned to Newark, the police department offered no services for returning vets, and he says he probably wouldn’t have applied for help anyway, fearing a stigma. “I just went back to work like nothing happened,” he said.

He lasted eight days in police uniform before his first suicide attempt. Tormented by memories of an explosion at the Baghdad airport that killed a favorite K-9 patrol dog, unnerved by crowds, spooked by loud noises and argumentative with superiors, “I tried to eat my gun.”

His wife drove him to a nearby veterans hospital, where Thomas was diagnosed with severe PTSD. Thomas, now 57, is an advocate in the non-profit military and veterans support group, The Wounded Warrior Project.

The vet-to-cop pipeline

Policing has long been a favored career choice for those who have enlisted in the armed forces.

Today just 6 percent of the population at large has served in the military, but 19 percent of police officers are veterans, according to an analysis of U.S. Census data performed by Gregory B. Lewis and Rahul Pathak of Georgia State University for The Marshall Project. It is the third most common occupation for vets behind truck driving and management.

The attraction is, in part, the result of a web of state and federal laws — some dating back to the late 19th century — that require law enforcement agencies to choose veterans over candidates with no military backgrounds.

In states with the most stringent hiring preferences, like New Jersey and Massachusetts, a police applicant who was honorably discharged from the military leaps over those who don’t have those credentials. Disabled veterans are favored over military veterans with no documented health concerns. William Thomas, the PTSD-afflicted Newark cop, secured a place on the sergeant's promotions list because of his time overseas with the New Jersey Air National Guard.

The Obama administration helped expand the preference: in 2012, the Department of Justice provided tens of millions of dollars to fund scores of vets-only positions in police departments nationwide.

Official data on the impact of veteran-cops is scarce. Nearly all of the 33 police departments contacted by The Marshall Project declined to provide a list of officers who had served in the military, citing laws protecting personnel records, or saying the information was not stored in any central place. The Justice Department office that dispenses grants to hire cops and study policing said it has no interest in funding research into how military experience might influence police behavior.

“I reject the notion that a returning veteran, who has seen combat, should cause concern for a police chief,” said Ronald L. Davis, who headed that office in the Obama administration. “I would even hire more if I could.”

But even those who advocate hiring combat veterans as police officers have raised alarms. The Justice Department and the International Association of Chiefs of Police put out a 2009 guide for police departments to help with their recruitment of military veterans. The guide warned: “Sustained operations under combat circumstances may cause returning officers to mistakenly blur the lines between military combat situations and civilian crime situations, resulting in inappropriate decisions and actions—particularly in the use of less lethal or lethal force.”

“A PTSD moment"

In 2012, Iraq War veteran and Albuquerque police officer Martin Smith responded to a call about a suspicious black SUV. Seconds later, he shot and killed the unarmed motorist through the driver’s side window. In court papers, lawyers for the dead man’s family said Smith “later told his co-workers that he ‘blacked out’ and had a ‘PTSD moment’” during the shooting. Smith had returned from deployment at a time when law enforcement across the country “was really trying to figure out how best to deal with the number of folks who were being activated,” then–police Chief Ray Schultz said in depositions. According to court papers, Smith re-joined the force with a 100 percent disability rating, suffering from flashbacks, blackouts, and waking-nightmares; nevertheless, the department assigned him to patrol a high-crime area of town known as “the War Zone.”

The Albuquerque force has been cited by the Justice Department for a high rate of unjustified police-involved shootings. According to documents provided to the Marshall Project by Albuquerque police, of the 35 fatal shootings by police between January 2010 and April 2014, 11, nearly one-third, were by military veterans. Neither the Albuquerque Police Department nor the city attorney responded to questions about the shooting.

In two other cities that agreed to provide data to The Marshall Project — Boston and Miami — internal police records indicate that officers with military experience generate more civilian complaints of excessive force. Without knowing such details as age, duration of military service and the officers’ assignments, it is impossible to rule out other factors, but in both cities the difference is noteworthy:

In Boston, for every 100 cops with some military service, there were more than 28 complaints of excessive use of force from 2010 through 2015. For every 100 cops with no military service, there were fewer than 17 complaints. Lt. Detective Michael P. McCarthy, a spokesman, said the department would look into the apparent disparity. He added that veterans tend to be younger and more likely to be assigned to units such as drug and gang enforcement, which attract more complaints. “We try to culturalize and de-sensitize these veterans, teach them [about] unconscious bias, de-escalation tactics,” said the city’s police commissioner, William B. Evans, in an interview.

In Miami, based on data from 2013 through 2015, for every 100 veterans on the force, 14 complaints were filed; for every 100 officers without military service, 11 complaints were filed.

The Marshall Project also obtained data for the Massachusetts state police, which showed no significant difference in complaints against vets and non-vets for excessive force.

The International Association of Chiefs of Police (IACP), the largest organization of policing executives, published in 2009 a survey of 50 police chiefs about their experiences integrating returning soldiers. Fourteen percent reported more citizen complaints against veteran officers, 28 percent reported psychological issues, and 10 percent saw excessive violence.

Another indicator can be found in a survey of nearly 8,000 police officers by the Pew Research Center. Asked last year whether they had ever fired their guns in the line of duty, 32 percent of military veterans said yes, compared to 24 percent of non-vets.

The Other ‘Don't Ask, Don't Tell'

When police officers return to work after a military deployment, they cannot be automatically required to sit for a mental health evaluation — the federal Uniformed Services Employment and Reemployment Rights Act prohibits it. Because of the Americans With Disabilities Act, police departments can’t reject a job candidate for simply having a PTSD diagnosis.

The only time most of America’s law enforcement officers, military veterans or not, are required to sit for a mental health analysis is when they first apply to join a police force, and the rigor of the screening varies widely. Fewer than half of the nation’s smallest police departments conduct pre-employment psychological testing at all, according to the Bureau of Justice Statistics.

Many other departments offer “screenings” in name only — in some cases simply a computerized test with no face-to-face interview — says Stephen Curran, a Maryland police psychologist who has researched the transition from the military to policing.

Where there is systematic testing of would-be police, military veterans are more likely to show signs of trauma.

Matthew Guller, a police psychologist, is managing partner of a New Jersey firm, The Institute for Forensic Psychology, that works with about 470 law enforcement agencies across the Northeast, screening for impairment.

Of nearly 4,000 police applicants evaluated by Guller’s firm from 2014 through October of 2016, those with military experience were failed at a rate higher than applicants who had no military history — 8.5 percent compared to 4.8 percent.

The higher rates of trauma are exacerbated by the fact that service members suffering PTSD often aren’t diagnosed and keep quiet about their suffering. Although up to 20 percent of those deployed to Iraq and Afghanistan have PTSD, only half get treated, according to a 2012 National Academy of Sciences study. Veterans are 21 percent more likely to kill themselves than adults who never enlisted, according to an August report by the U.S. Department of Veterans Affairs.

PTSD and traumatic brain injuries have been called the “signature injuries” of the wars in Iraq and Afghanistan. Experts say trauma is cumulative, so the transition from one potentially violent profession, the military, into another, policing, can compound the risk.

Officers with a history of mental health problems — even those who have been treated and are now healthy — can pose a two-fold problem for departments who hire them. First, their history can become a liability if the department is sued. Second, it can be used to attack their credibility on the stand if they’re called to testify.

Mental health advocates and union leaders say the safety net for struggling cops at most police departments is minimal to nonexistent. Even departments sensitive to mental health issues are in a difficult position: top brass needs to be able to take unstable cops off the street lest they hurt someone or themselves on the job. Yet cops must feel they can ask for help confidentially, without jeopardizing their careers, or “you're never going to get cops to come forward” for treatment, says Brian Fleming, a retired Boston Police sergeant who ran the department’s peer support unit from 2010 to 2014.

The lack of official attention in many cities has spurred police unions and individual cops to construct their own safety nets, programs where cops can open up about pain they would never show at a station house.

“I’ve never been at a roll call and someone says ‘Know what, Sarge? I feel sorta sad today,’” said Andy Callaghan, a Philadelphia police narcotics sergeant who spends his spare time at the Livengrin Foundation for Addiction Recovery, outside of Philadelphia, counseling police and combat veterans with mental health issues.

In the last decade, mental health and addiction programs geared towards cops and military veterans have begun to spring up around the country.

“This is an untapped market,” says Clare Seletsky, a manager at Livengrin, which launched the First Responder Addiction Treatment program in 2011. “We need to expect to be treating this population for the next 50, or 60, years,” Seletsky says of police who are also military veterans.

“Early intervention is the key,” says Callaghan. “Waiting for someone to self destruct is what we do, and it's terrible.”

‘Why take the test?’

Boston’s police commissioner has another problem with the vet-to-cop pipeline. In a city whose residents are more than half people of color, the Boston Police Department is two-thirds white. Like many big-city chiefs, Evans is struggling to recruit African-Americans and Latinos to build greater trust with city neighborhoods they serve. But under the state’s strict preference, military veterans go to the head of the line. And Massachusetts veterans reflect the racial demographics of an overwhelmingly white state, not urban Boston. Almost nine out of 10 military veterans who live in Massachusetts are white.

Attracting non-white recruits is hard enough without the veterans’ preference, Evans notes. “Obviously, it’s a tough job for a minority,” he says. “They are in a community that really doesn’t like them. And they think they are a sellout, you know, ‘Uncle Toms.’”

Seattle Police Chief Kathleen O’Toole, who was a predecessor of Evans in Boston, said the preference also makes it hard to change the culture of policing. While she can list many vets who have been “great cops,” she said, “I want to attract people with very different skill sets. We are facing complicated issues with people who are in crisis every day. Why wouldn’t I want people who majored in human services? Or psychology or sociology?”

A Marshall Project analysis of veteran preference laws found that civil service rules in all 50 states and the federal government have historically given an edge to military veterans in law enforcement hiring, promotion or job protection. The most common advantage is an extra five points on the entrance exam, or 10 points for a disabled veteran.

Massachusetts and New Jersey have the most favorable laws for vets seeking police work. An honorably discharged veteran skips to the top of police hiring lists, which makes it more difficult to hire women and minorities.

In New Jersey, eight out of 10 veterans are white men. Only 5 percent of veterans who reach the stage of being screened for police work are women.

Until 2015, Jersey City, where only 32 percent of residents are white, went a decade with no black cops above the rank of sergeant. Jersey City has opened a new police recruitment office, headquartered in a bustling African-American neighborhood, which offers applicants free police test preparation classes and help finding work while they snake through the months-long hiring process.

“Correcting things that have been in place for decades is obviously not easy,” says Jersey City Mayor Steven Fulop. “The civil service process can make it difficult.”

In Boston, without veteran status, applicants need a near-perfect score on the police exam to land a spot in the Boston Police Academy. “It’s pointless,” says Jacobo Negron, President of the Massachusetts Latino Police Officers Association, about taking the Police Academy entrance exam. “Why take the test?”

In an attempt to circumvent the state’s pro-veteran hiring preferences, Evans has revised a once defunct police cadet trainee program and has ordered his recruiters to seek out young minority Bostonians. After a two-year period, these new cadets are eligible to become full-time cops.

“The whole idea of cadets is to basically counteract the absolute veterans preference, which seems to be all white,” Evans says. The first class of 42 junior officers — only a quarter of them white — were sworn in in mid-November.

Outside of the city, more than a half dozen localities in Massachusetts have opted out of the civil service system altogether. “You are seeing so many returning veterans,” says Terry Cunningham, who recently retired as police chief in Wellesley. Wellesley voted to take its police out of civil service in 2010. “For the most part they were white males. We weren’t getting any diversity in the department.”