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Excerpt

I. What does it really take to kill someone with “compression asphyxia”?

Over the years, medical examiners and plaintiff’s attorneys have advanced a variety of speculations to explain the arrest-related deaths of suspects for which no medical cause is readily apparent.

This parade of horribles has included hog-tying, positional (prone) asphyxia, neck restraint, pepper-spraying, and cardiac disruption (electrocution) caused by conducted electrical weapons. And one by one, impartial scientific investigation has largely discredited these assertions.

Now a highly credentialed international research team offers fresh evidence that another alleged cause of ARD is a myth as well. That’s “compression asphyxia,” a fatal interference with breathing supposedly caused by officers kneeling, sitting, or lying on a resistant suspect’s upper body to establish and maintain control for handcuffing.

While compression asphyxia is a commonly documented phenomenon in certain real-world circumstances, it’s “crazy” to consider it a realistic possibility in the context of police street practices, according to the researchers’ leader, Dr. Mark Kroll, an adjunct professor of biomedical engineering at the University of Minnesota and California Polytechnic University.

“Weight on the chest as a cause of arrest-related death?” Kroll says. “No way!”

Details of his group’s findings are newly published in the journal Medicine, Science and the Law. That report is a dense thicket of technical language, but in an exclusive interview with Force Science News, Kroll recently translated its essence into laymen’s terms.

EXPERT CREDENTIALS. With more than 370 patents to his name, Kroll is one of the most prolific inventors of medical devices in the world. He has won the highest international award in biomedical engineering, and in the law enforcement realm his scientific input was critical to the development of the TASER CEW.

He appears frequently as a consulting witness in police litigation, and it was in court that he first encountered the plaintiff claim that compression asphyxia could explain ARDs that seem otherwise baffling. In light of the truth behind other faddish but specious “causes” of ARD, he decided expert investigation was warranted.

He recruited four other PhDs or MDs from British and American universities to join him, including a forensic pathologist, a specialist in the mechanical strength of human bones, an authority on compression deaths from “crowd crush,” and a physician trained in emergency medicine who has studied ARD injuries.

THREATS KNOWN/UNKNOWN. First, the team established the known basics of death from compressive pressure on the human body.

“A fully loaded soft-drink vending machine weighing 1,100 pounds falling on you will kill you,” Kroll says. “So can a car crushing you when a jack collapses, or the impact of a steering wheel slamming against your chest in a collision. But important experiments at the University of California-San Diego showed that a prone, hog-tied subject could withstand 225 pounds of weight on his back and still breathe just fine.”

The team located official records from centuries back when lawbreakers and religious martyrs were subjected to “pressing” under weights piled on their chests for purposes of interrogation or execution. One highway robber bore 350 pounds for half an hour, while a woman was pressed to death in 15 minutes by an estimated minimum of 700 pounds.

“The pressing data shows that about 400 pounds on the chest was survivable because of diaphragmatic breathing, with communication still possible,” Kroll says. “But over 626 pounds was fatal.

“A major mechanism of compression deaths” is the generation of what’s known as “flail chest,” he explains. This involves the fracturing of enough adjacent ribs in two or more places each to cause a segment of the rib cage to break free and move independent of the chest wall.

Such major damage “prevents effective breathing and can cause death even after the source of compression is removed,” Kroll says. “With five to seven ribs involved, you’re shot. Even breathing via your diaphragm (located below the chest) won’t help at that point.”

What he and his colleagues sought to objectively identify for the first time was the specific amount of traumatic force necessary to break enough ribs to cause flail chest. In effect, how much weight on the upper body is required to kill someone via compression asphyxia.

RESULTS. Obviously, testing live volunteers until they died was not an option. But based on the known strength of rib bones, the researchers were able to design a “biomechanical model” of the thorax that allowed for mathematical computations that approximate human experimentation.

From that, they predict a practical rule of thumb, Kroll reports: roughly 570 pounds (they calculated 573 plus or minus 57 pounds) of pressure on the front or back of the torso of a male subject in his 20s or 30s is required to break six ribs sufficiently to cause fatal flail chest.

“In other words,” Kroll says, “it would take two 285-pound cops standing and balancing on the back or chest of a suspect to produce compression asphyxia. And that’s simply not going to happen in the real world.”

Even if an officer were to drop forcefully on his knees onto a suspect, “it wouldn’t significantly change things,” Kroll says. “The weight of dynamic force from dropping needed to cause death is actually higher than the amount of necessary static weight piled on a subject, because the rib cage has an impressive built-in ability to absorb the physical shock of sudden impact.”

Kroll acknowledges limitations to the study. The team’s calculations did not extend to female subjects, children, the elderly, or those with bone disease. He believes, though, that the findings are relevant for most subjects who resist arrest and might end up in a compression situation.


Thoughts?
 

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I always thought that compression asphyxia came as a result of pressure applied against the diaphragm.
 
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I think a lot of that is going to depend on the person being kneeled on. If they're old or have brittle bones they're going to feel it if a 300 lb man kneels on their back. It's like every scenario we discuss here. The answer is, "it depends". I've read about people who were young and strong getting killed by a single punch to the head. I once saw a HS classmate get hit in the head with a baseball bat and walk away like it was nothing.
 

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I think a lot of that is going to depend on the person being kneeled on. If they're old or have brittle bones they're going to feel it if a 300 lb man kneels on their back. It's like every scenario we discuss here. The answer is, "it depends". I've read about people who were young and strong getting killed by a single punch to the head. I once saw a HS classmate get hit in the head with a baseball bat and walk away like it was nothing.
Kroll acknowledges limitations to the study. The team’s calculations did not extend to female subjects, children, the elderly, or those with bone disease.
 

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"...important experiments at the University of California-San Diego showed that a prone, hog-tied subject could withstand 225 pounds of weight on his back and still breathe just fine."

Is that a scientific experiment, or more the "I experimented in college" kind of thing?

Anyway, it sounds like a valid study, but it seems that it doesn't really answer the question. Presumably, if five adjacent ribs are fractured in two or more places, it wouldn't be a "death for which no medical cause was readily apparent." The question is really if asphyxiation can be caused by compression that's not severe enough to crack all those ribs.
 

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I had a motorcycle get off back in the mid 1970's that separated all of my ribs on the left side and 3 on the right side. The MDs at the ER were worried I would die from it due to the compression injury of hitting the pavement at 45 mph. They taped my entire rib-cage so tight I had to breathe through my diaphragm for 3 weeks.
It was pretty painful. But I did it.
 

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"...important experiments at the University of California-San Diego showed that a prone, hog-tied subject could withstand 225 pounds of weight on his back and still breathe just fine."

Is that a scientific experiment, or more the "I experimented in college" kind of thing?

Anyway, it sounds like a valid study, but it seems that it doesn't really answer the question. Presumably, if five adjacent ribs are fractured in two or more places, it wouldn't be a "death for which no medical cause was readily apparent." The question is really if asphyxiation can be caused by compression that's not severe enough to crack all those ribs.
And that particular question is so beyond doubt as to be rhetorical. The study seems to answer the question of how many pounds of pressure does it take to break ribs?
 

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I once had a sports car fall on me when I was working under it. I was a strapping 20 year old in pretty good shape and the gas tank pinned me to the ground. I was able to breath, but it took a lot of effort. My friends lifted the car off me within a minute or so. My very limited experience supports the author's conclusion.
 

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Just IMO it's over-simplified, however when you do research you do have to define the parameters so you can analyze and eliminate or include them. They focused on chest compression.

But during a struggle, there are many factors, the perp doesnt just lie down and have cops kneel on them. The perp could already be in oxygen deficit from fighting or running. Could have nose or throat clogged with blood. Could have head trauma/banged head on ground.

Some of this would also show up in examinations later, some not (O2 deficit).

One other point is that when you do restrict someone's breathing, they often panic. It may not even be conscious. Fear, pain, inability to get enough air...and then once they panic they use up more air and the cops come down even harder.

IMO the technique should be used carefully and the article seems to dismiss the dangers, implies that the technique is ok as is.
 

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Well the real way to prevent this issue is simply "don't mess with the cops" .....turn around, comply and breathe easy. Just sayin.
 
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Kroll acknowledges limitations to the study. The team’s calculations did not extend to female subjects, children, the elderly, or those with bone disease.
Even though the OP used the phrase, "... no medical cause is readily apparent." He also must also be ignoring the 8% of the population with asthma - that we know about. There are a lot cases undiagnosed. About 5,000 asthma sufferers die a year from asphyxia without any weight on their chest at all. Sudden stress (like a cop sitting on your chest) can be an asthma attack trigger.

My other observation is that a cop sitting or kneeling on someone's chest or upper back is unnecessary and not a great technique. Sure, it works if the cop is bigger than the suspect, the suspect has already been stunned or there are other cops helping pin other parts of the body. But if you have studied judo or wrestling, as I have, or even if you watch MMA, you'll notice that a good mount position controls the hips, not the chest. If you sit or kneel on the chest or upper back of someone with grappling skills, you are going to go flying! You want to control the hips with your weight. The cop in the photo below is in a solid control position.
cop pin.jpg
 

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Even though the OP used the phrase, "... no medical cause is readily apparent." He also must also be ignoring the 8% of the population with asthma - that we know about. There are a lot cases undiagnosed. About 5,000 asthma sufferers die a year from asphyxia without any weight on their chest at all. Sudden stress (like a cop sitting on your chest) can be an asthma attack trigger.

My other observation is that a cop sitting or kneeling on someone's chest or upper back is unnecessary and not a great technique. Sure, it works if the cop is bigger than the suspect, the suspect has already been stunned or there are other cops helping pin other parts of the body. But if you have studied judo or wrestling, as I have, or even if you watch MMA, you'll notice that a good mount position controls the hips, not the chest. If you sit or kneel on the chest or upper back of someone with grappling skills, you are going to go flying! You want to control the hips with your weight. The cop in the photo below is in a solid control position.
View attachment 185314
I agree, I used to place a knee at the juncture of the shoulder and neck. That's a much more effective area than the back.

In the pic you put up, I'd have been using the left leg to control the shoulder/neck, not the back with my right knee. By placing the weight on the juncture I used, the person couldn't turn/twist their body. Control the head/neck, you control the body. Basic principles taught in the h2h/knife courses.
 

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I agree, I used to place a knee at the juncture of the shoulder and neck. That's a much more effective area than the back.

In the pic you put up, I'd have been using the left leg to control the shoulder/neck, not the back with my right knee. By placing the weight on the juncture I used, the person couldn't turn/twist their body. Control the head/neck, you control the body. Basic principles taught in the h2h/knife courses.
I think there is some good form (pun intended) shown here. This shows two Swedish cops who were sunbathing off-duty when they saw a purse snatching, chased the suspect down and restrained him.
swedish bikini cops.jpg
 

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I think there is some good form (pun intended) shown here. This shows two Swedish cops who were sunbathing off-duty when they saw a purse snatching, chased the suspect down and restrained him.
View attachment 185322
Both girls are holding his shoulders down. He can't turn on them being restrained like that. Now take the girls knee and move it to the top of the shoulder at the juncture of the head, he's immobilized by a party of one. If she planted her left knee thusly while straddling his head, she'd have been in a better position of control.
 

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I'm glad he pointed out the elderly and kids. Compression Asphyxia is a legitimate killer of poorly restrained kids. I restraint trained with the Cornell University Therapeutic Crisis Intervention program and even trained with the professors that developed it once. It's such a risk with kids that by the time I was leaving the field of at risk youth work TCI was going away from physical restraint to overwhelming the kids with staff to control them. Oddly enough, a couple years of high school wrestling taught me a lot about weight management on the top and wearing down someone on the bottom. It transitioned pretty smoothly to the restraints if you paid attention and knew when to ease up on the addition of weight. We had to be physical but not too physical. Most injuries and deaths occur when the staff does not let up on using their weight when the kid has given up. That's when bad things happen.
 
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I think there is some good form (pun intended) shown here. This shows two Swedish cops who were sunbathing off-duty when they saw a purse snatching, chased the suspect down and restrained him.
View attachment 185322
If I'm ever busted by two Swedish female cops (hell, one), they won't have to restrain me, I'll be grinning like a damned Cheshire cat while they walk me away.

Here's the thing, I think that maybe don't try to fight a cop and you won't get sat on? I don't know what it takes to kill a man by sitting on his chest, but I truly believe cases like it are few and far between. I think it's just another thing "some people" use as another way to protest and hate on police officers.
 

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I wonder if the good Dr. has ever witnessed someone suffocate in a ditch cave in. A person buried to the neck must be rescued rapidly. I have no idea of the weight involved, but the compression on the whole body overwhelms the ability to breathe.

Saw the Dr. had a hand in Taser development. They are wonderful tools. However, IF you are unlucky and taser someone with an underlying arrhythmia, it can be fatal. Many people do not know that when you have a heart attack, the application of an electrical shock by a defibrillator is actually not starting the heart beating, but stoping the heart from an arrhythmia that is so fast the heart muscle cannot pump blood. The shock stops the heart from beating fast, and unless there are other issues, the heart starts again on its own. Or not.

In law enforcement, proper application of appropriate force is a good thing. Application of excessive, inappropriate force is not. Training is the key.
 
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