For decades, police across the United States have been warned that the common tactic of handcuffing someone facedown could turn deadly if officers pin them on the ground with too much pressure or for too long.

Recommendations first made by major departments and police associations culminated in a 1995 federal safety bulletin that explained keeping someone on their chest in what’s known as prone restraint can dangerously restrict breathing. The solution: Once cuffed, turn them onto their side.

Yet today, what some officers are doing on the street conflicts with what has long been recognized as safe, a deadly disconnect that highlights ongoing failures in police training, an Associated Press investigation has found.

Cases involving prone restraint are among more than 1,000 AP documented over a decade of people who died not by gunshot but after officers used force that is not meant to kill. In all, at least 740 of these encounters involved prone restraint, making it the most prevalent tactic. It was also commonly misapplied.

Each state writes its own standards, and individual departments and training centers determine what officers hear in classrooms and gyms. The safest techniques don’t always filter down to officers.

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PATCHWORK OF REQUIREMENTS

What officers learn about the risks of prone restraint depends on geography.

Nearly all states have a Peace Officer Standards and Training agency that sets out what must be taught, so AP asked each commission whether it requires instruction on positional asphyxia, which happens when the chest can’t expand, starving the body of oxygen. Among the states that responded, 10 said they did not require positional asphyxia training and 20 states said they do include that training.

MANY OFFICERS HAD TRAINING, OTHERS HAD NONE

To understand what officers knew before deaths involving prone restraint, reporters scoured thousands of pages of interviews and depositions.

In nearly 100 cases, AP identified documents that showed whether officers had training in or otherwise knew the risk of positional asphyxia. In 80 deaths, at least one involved officer had been trained in or knew the potential dangers, though they did not always turn someone off their stomach promptly. Officers in another 14 deaths said they had no training and did not know the risks; could not recall training; or — in a few cases — were trained that prone position is safe.

MYTHS PERSIST

Some officers repeated two common misconceptions that experts and trainers have long tried to dispel: That if someone can talk they can breathe, and that someone struggling for air is resisting arrest.

To speak, air must move across the vocal cords in the throat. To inhale oxygen and expel carbon dioxide, air must travel to and from the lungs. The short additional distance can be huge if someone is laboring to breathe.

“There’s a big difference between fighting the officers and fighting for breath,” said Seth Stoughton, a University of South Carolina law professor and national use-of-force expert who as a former officer and police trainer has written extensively about prone restraint.

LIMITS OF NEW LAWS

California’s Legislature passed a 2021 law that said departments “shall not authorize techniques or transport methods that involve a substantial risk of positional asphyxia.” The legislation’s sponsor said he wanted to limit prone restraint. But the law hasn’t stopped some instructors at state-certified training centers from continuing to teach that holding someone facedown is a best practice.

Among the most senior instructors in California is David Rose, who in his 40 years as a trainer has taught thousands of officers that prone restraint is safe. Rose said he instructs officers to hold a person facedown with as little pressure as necessary, unless they are combative. He said the methods he teaches don’t run afoul of California’s law because prone restraint doesn’t carry a serious risk of positional asphyxia.

“Positional asphyxia doesn’t happen at all. In the field, it doesn’t happen,” Rose said in an interview at a regional training center in Sacramento.

“Putting weight on a person’s back in a prone position does not lead to them expiring unless it’s enough that it can actually squash them,” he said.

Rose bases his belief on studies produced by police-aligned lawyers, professors and experts who defend officers when they’re sued in court.

Officers almost always used prone restraint with other force, and within AP’s database medical officials cited prone position or asphyxia due to restraint as a cause or contributing factor in 61 of the 740 cases that involved the maneuver during the investigation’s 2012-2021 timeframe. In dozens of other cases, officers used prone restraint and “restraint” was cited as causing or contributing to the death, but prone position or restraint was not specified.

In many other cases, the cause of death focused on drugs or medical conditions instead of force. Due to the suppression of records, reporters were not always able to get the official determination.

AP contacted the California Commission on Peace Officer Standards and Training and asked whether Rose’s teachings on positional asphyxia align with state requirements. “POST is taking action and has notified the (Sacramento training) center that they are not compliant with the law. The issue will be remedied,” spokesperson Meagan Poulos wrote in an email Monday.

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Contributing to this story from the Howard Center for Investigative Journalism at the University of Maryland were Sean Mussenden and Mary Dalrymple.

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This story is part of an ongoing investigation led by The Associated Press in collaboration with the Howard Center for Investigative Journalism programs and FRONTLINE (PBS). The investigation includes the Lethal Restraint interactive story, database and the documentary, “Documenting Police Use Of Force,” which premiered April 30 on PBS and is available online. To view stories by journalists at the Howard Center for Investigative Journalism programs, go here.

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The Associated Press receives support from the Public Welfare Foundation for reporting focused on criminal justice. This story also was supported by Columbia University’s Ira A. Lipman Center for Journalism and Civil and Human Rights in conjunction with Arnold Ventures. The AP is solely responsible for all content.

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Contact AP’s global investigative team at [email protected] or https://www.ap.org/tips/