(CNN) In videos that show George Floyd's killing in Minneapolis police custody, an officer holding down the Black man's ankles says, "I just worry about excited delirium or whatever." Another officer responds: "That's why we have the ambulance coming."
But Floyd did not meet any of the 10 criteria used by many to diagnose "excited delirium," a police surgeon testified later in the murder trial of the second officer, Derek Chauvin. And an independent autopsy found the 46-year-old died during the 2020 encounter of "asphyxiation from sustained pressure" when his neck and back were compressed.
That same year, Elijah McClain was diagnosed with "excited delirium" by paramedics in Aurora, Colorado. McClain was placed in a carotid hold by police and injected with ketamine when paramedics arrived. The medics never checked the 23-year-old Black man's vital signs, talked to him or touched him before making the diagnosis, a Colorado grand jury found. McClain was declared brain dead three days later.
And "excited delirium" was among the causes of death listed for Daniel Prude in Rochester, New York, along with complications of asphyxia in a setting of physical restraint and acute PCP intoxication, according to a medical examiner's report. The 41-year-old Black man was having a mental health emergency in 2020 when officers covered his head with a mesh hood and held him prone on the ground before he stopped breathing. He was declared brain dead and died a week later.
Excited delirium is used as a field diagnosis by first responders across the country. Officers in many police departments are officially taught to look for "superhuman strength" and "police non-compliance" as symptoms of a syndrome that could kill the subject of an emergency call or induce that person to kill them.
"Pain tolerance," "unusual strength," "agitation" and being "inappropriately clothed" are other potential features of the syndrome listed in an American College of Emergency Physicians white paper cited in expert testimony in Chauvin's trial, though the doctors' group told CNN it never officially endorsed the 2009 document.
Similar descriptions of excited delirium can be found in police training materials used in several major US cities. Officers are called upon to make split-second decisions to identify the condition in order to preserve their own safety and the safety of their subject, including potentially by using force. Such a determination also later can be key to how the public, their supervisors or the courts view the incident.
Authorities claimed these Black men had excited delirium just before they died. But the diagnosis itself is a problem and should be abandoned, a new study says. But a new study from doctors at Harvard, the University of Michigan and Massachusetts General Hospital, as well as civil rights lawyers, says the term excited delirium is "scientifically meaningless" and has become a "catch-all for deaths occurring in the context of law enforcement restraint, often coinciding with substance use or mental illness, and disproportionately used to explain the deaths of young Black men in police encounters."
Indeed, a case that helped cement the term's widespread use unfairly targeted Black people. And while there is no national database of excited delirium deaths in police custody, one study of 166 cases found that Black people made up 43% of those deaths from 2010 to 2020 nationally. Black or African Americans made up 13% of the population in the most recent US Census.
In rejecting the term outright, the coalition of physicians, civil rights attorneys and researchers who worked on the Physicians for Human Rights study wants it stricken from the official vocabulary used by emergency medicine technicians, doctors, law enforcement and medical examiners.
It should be replaced, they say, with an approach that prioritizes immediate treatment of the underlying causes of the behavior encountered by first responders. A better approach might also mean expanding the type of professional who responds to emergency calls to include those with specialized training in mental health and social work.
The problem with "excited delirium" goes deeper than the phrase itself, said Dr. Michele Heisler, medical director of Physicians for Human Rights, a co-author of the study and a professor of public health and internal medicine at the University of Michigan.
"We were concerned about the concept," she explained, pointing to the myriad of symptoms often listed under the term's umbrella.
"People can become agitated or delirious due to multiple factors, ranging from alcohol withdrawal, drug overdose, psychosis. ... What we're arguing is that these underlying causes require medical attention, rather than forcible restraint by police."
Officers learn in academy training to restrain and control a subject until medics -- who are supposed to make any medical diagnosis -- get to the scene.
"Training typically involves recognizing signs of ED (excited delirium) and summoning emergency medical services immediately in such cases," Sherri Martin, national director of wellness services for the Fraternal Order of Police told CNN.
Police also sometimes lean heavily on paramedics to use powerful tranquilizer drugs so subjects experiencing what they say is excited delirium stop resisting. Later on, coroners and medical examiners may use the same language, including as part of autopsies.
An umbrella term like excited delirium can also help facilitate the training process, Sergeant Tony Lockhart, crisis intervention trainer for King's County, Washington, said. "You call it whatever you want; I see these behaviors." Aggregating them into one idea, he said, is "helpful in some areas, to at least give us a different title to think about in our head."
Even so, the term is not listed in the World Health Organization's International Classification of Diseases nor the Diagnostic and Statistical Manual of Mental Disorders, tools seen as the standard for medical diagnosis across the world. The American Medical Association does not support it as a diagnosis, and the American Psychiatric Association, which does not recognize it as a mental disorder, referred to it in 2020 as "too non-specific" and its criteria unclear, adding that no rigorous studies had been done to validate it.
The term's roots also raise questions. Excited delirium was first used in the 1980s, when a deputy chief medical examiner in Florida publicized a theory that Black women could die from "combining sex with cocaine use," the Physicians for Human Rights study details.
"For some reason, the male of the species becomes psychotic and the female of the species dies in relation to sex," Dr. Charles Wetli of Miami-Dade County told the Miami Herald at the time, adding that it might be the genetic makeup of Black people that predisposes them to dying.
The modern incarnation of the term, the report says, was popularized by the 2005 mass-purchase and distribution of one book to police departments by the makers of TASER guns, Axon Network. The company distributed those copies to bring awareness to excited delirium, it told CNN in a statement.
"Superhuman strength," one of the criteria to identify excited delirium listed in the 2009 ACEP report, is completely unfounded, Heisler said. Instead, "if you're frightened, it's going to be an intense adrenergic response," she said. "You're going to have a strong fight-or-flight response. (But) it's not a response that in and of itself is going to cause death."
Adrenaline-related responses are responsible for an increase in heart rate, constriction of blood vessels and dilation of pupils, she said. But it's unfounded "that you can just suddenly scare yourself to death -- which in a way seems to be the implied physiological mechanism of excited delirium. But it certainly is the case that it's very frightening," Heisler said.
In their report, the Physicians for Human Rights authors used the American Psychiatric Association's definition of delirium: "a neurocognitive disorder characterized by a 'disturbance in attention and awareness that develops over a short period of time and is not better explained by another preexisting, evolving, or established disorder.'"
In layman's terms: "Delirium is a symptom of an underlying cause and not an independent diagnosis," Heisler said.
A person with delirium may show "fear, agitation, or euphoria, as well as reduced awareness of the environment," and delirium itself is usually a sign of an underlying problem, such as organ failure, infection, lack of oxygen, low blood sugar levels, drug side effects, intoxication or withdrawal, according to the Physicians for Human Rights report.
In any case, "delirium ... wouldn't be defined just by the need for use of force," said Dr. Debra Pinals, director of the American Psychiatric Association's Council on Psychiatry and Law.
The report also raises concern over the use of the term in medical examiners' and coroners' reports as a cause of death. "Delirium is not itself considered a cause of sudden death," it reads.
"You can't say that someone dies from any form of delirium," Heisler said. "It's like saying, what is the cause of death? Chest pain. What is the cause of death? I don't know, shortness of breath. In a way, it's as nonsensical."
The National Association of Medical Examiners has never issued "any type of consensus on excited delirium and as an organization have not formally 'recognized the condition as a diagnosis,'" it told CNN in a statement. Its president, Dr. Kathryn Pinneri, said, "I suspect it is accepted among many NAME members."
In the field and in medical settings, the treatment for delirium is to address the underlying cause with medical care such as hydration, medication, and pain control, Heisler said. Restraints are actively discouraged, according to the Physicians for Human Rights report, and "never include prone or neck restraints, and are monitored by an independent medical oversight organization."
But Lockhart said in his trainings, he teaches officers to restrain subjects in "altered states" -- for their own safety and for the safety of others involved -- as swiftly as possible. "The longer it goes on, definitely more danger to the subject, definitely more danger to every officer involved and for that matter, any other folks around," he said.
Lockhart's view is that there should be as many officers around the subject as possible. "In an ideal world ... one officer grabs one leg, and another grabs one leg, another grabs an arm and other grabs an arm, obviously giving commands and try to do that quickly as we can to get them detained to get that medical person access to that individual."
But in reality, restraining a person in distress can be much more challenging, especially when only one or two officers are on the scene, he said.
The exhaustive training police officers go through as cadets on excited delirium -- and continue to attend as mandatory refreshers throughout their careers -- has shown, even in court, to be part of the problem.
"The fact is, that term has been increasingly co-opted by nonmedical professionals and being used in nonclinical discussions or nonclinical realms," said Dr. Jeffrey Goodloe, member of the American College of Emergency Physicians board of directors and chief medical officer for the EMS system for Metropolitan Oklahoma City and Tulsa.
"There's quite a spectrum of educational programming, even within the house of medicine between different specialties. And then obviously, that just becomes even more exponentially magnified, if you will, if you look at the various and sundry training programs within EMS agencies, ambulance services, fire departments, law enforcement agencies, and so there's not one national standard educational curriculum in this."
It's clear more training and dialogue between the law enforcement and the medical communities is needed, Goodloe said.
In Lockhart's 40-hour classes on excited delirium, he said he specifically tells officers, "You are not here to learn how to diagnose. You're looking at these behaviors so that you may alter your techniques to get a good solution so everybody's safe."
But a disconnect between first responder training -- based on the handful of studies that validate excited delirium -- and most academic medical literature has first responders acting out of step with the medical community.
"Police officers often feel like they're caught in the middle," said Martin, of the Fraternal Order of Police. "They're not thinking about all of these other voices. They show up to work every day to answer the calls, to do their job, and they want to have the tools and the knowledge to do the best job that they can."
Departments are also concerned with liability, she said, and they have an incentive to ensure officers are acting in accordance with regulations. "They don't want their department, their officer, their community to suffer the death of someone who was or may be suffering with excited delirium."
But changes in how police learn to respond to medical emergencies and mental health crises might not come easy. In Minneapolis, despite a 2021 directive from the city to halt excited delirium training, officers were still being trained on the concept months later, the Star Tribune reported in February. A digital slide from a training program shows the words "excited delirium" stricken through and below them, "severe agitation with delirium," is suggested as a better term, a video obtained by the newspaper shows.
During Chauvin's trial in April, Minneapolis Police Chief Medaria Arradondo testified the then-officer's actions and use of force during Floyd's arrest were contrary to department policy.
"There is an initial reasonableness in trying to just get him under control in the first few seconds," Arradondo said. "But once there was no longer any resistance and clearly when Mr. Floyd was no longer responsive and even motionless, to continue to apply that level of force to a person proned out, handcuffed behind their back -- that in no way shape or form is anything that is by policy. It is not part of our training, and it is certainly not part of our ethics or our values."
After an outcry over the term excited delirium in 2020, even the American College of Emergency Physicians -- whose definition remains the industry standard -- has tried to shift its language in new studies to "'hyperactive delirium."
"We recognize the term 'excited delirium' is increasingly being used in non-clinical medicine discussions and the term can produce a visceral and negative response, particularly among those in communities with complicated relationships with law enforcement or medicine," a spokesperson for the group told CNN in statement. "In clinical discussions, patient care, and especially safety of patients during care, must remain the focus."
Officers instead could be taught about an array of medical emergencies that may look like what's long been known as excited delirium but that may warrant different medical responses, "including heart attacks, drug or substance overdoses or withdrawals, acute psychosis, and oxygen deprivation," the Physicians for Human Rights report states.
"I think we're asking too much of police officers, and I think many of them are responding as best they can," Heisler said. "They're being told that you can put your knee on someone's back and that's safe. ... Are we expecting police officers to be trained in all these medical diagnoses? I mean, are we expecting doctors?"
The Physicians for Human Rights report's main recommendation is to nix the use of the term "excited delirium" altogether -- erasing it from training manuals and autopsy reports -- and encouraging medical associations that haven't done so to issue statements discouraging its use among their members.
Official responses to people experiencing mental and behavioral health challenges must improve, authors say in the report. That might start with rethinking who first responders should be, Heisler said.
"We need to think about -- are there other models? Could we bring in social workers, psychologists, trained behavioral health people, instead of having a group of armed, uniformed police that (are met) with a strong fight-or-flight response?" she said.
Lockhart, the crisis intervention trainer, agrees with this recommendation and sees major advantages in having team of "co-responders" that include police and mental health specialists.
"Just inherently, by that officer being there and listening to the mental health person deal with a subject, that officer is getting better because they're seeing things that work, new ideas, a different way of approaching something," he said, adding that an officer's presence helps ensure the safety of the mental health professional.
In the end, he said, the main benefit is that "the subject we're dealing with is getting better help and hopefully sooner" than they would otherwise.
On an institutional level, the Physicians for Human Rights study recommends establishing "independent oversight systems and mandat(ing) independent investigations of deaths in law enforcement custody," involving excited delirium in state and local governments, and it calls on Congress to do the same.
A report commissioned by Congress could answer many questions the study has identified, said Joanna Naples-Mitchell, human rights lawyer and researcher at Physicians for Human Rights.
"For example, where has excited delirium come up, and trying to understand why it is they are finding what seems to have been the case so far, that it's majority Black men and other people of color this term is being attributed to?" Naples-Mitchell said.
"And is it exclusively in the context of law enforcement where this term is coming up? Is it exclusively in the context of restraints being used that this comes up and deaths are attributed to excited delirium? There's a lot that legislators can do to really leverage their powers as investigators to look at this and bring public attention to it more broadly."