Forensic scientists decipher courtroom dispute over Floyd’s cause of death


Perhaps one of the most important witnesses to call in the Derek Chauvin murder trial is Dr. Andrew Baker. It was his duty to determine why George Floyd had died.

Dr Baker, the Hennepin County medical examiner, performed Mr Floyd’s initial autopsy and ultimately determined that his heart and lungs had stopped working as he was being overpowered, restrained and compressed by police officers.

The way Mr. Floyd died, Dr. Baker concluded, was homicide. And in the months that followed, almost everything he said in the autopsy report was analyzed and studied by experts and lay people alike.

In its opening statements last week, the prosecution said it would pursue an unusual strategy: to challenge aspects of Dr. Baker’s findings and introduce a reason he did not cite – a lack of oxygen – as the cause of Mr. Floyd died.

For its part, Mr Chauvin’s defense team told jurors that the pre-existing heart disease, high blood pressure and recent drug use documented by Dr Baker resulted in Mr Floyd’s death because of it. which they considered to be a cardiac arrhythmia.

As the trial approaches a phase where Mr Floyd’s cause of death takes center stage, we spoke with several forensic pathologists not involved in the case to explain some of the terms used in the proceedings, how they determine the cause and mode of death and how it relates to the case. Here is what we learned.

In the United States, some jurisdictions use coroners and others use forensic pathologists to determine the cause of some deaths, including those that occur in police custody. Unlike coroners, forensic pathologists must be physicians. Dr Baker is board certified in forensic pathology and is the chief medical examiner for Hennepin County. The Medical Examiner’s Office is an independent agency. It is not part of the application of the law.

When a person dies, a death certificate is completed for public health and legal reasons. The form includes a cause of death in the first section and contributing factors in the second section. “We usually have to find a cause,” said Dr Judy Melinek, a board-certified forensic pathologist. Anything important “that might not be right for a person is” contributing. “

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Pathologists describe the cause of death as the immediate injury or illness that results in death. It is “the disease or injury that sets off the fatal sequence of events without an intermediate cause,” said Dr Melinek.

Mode of death refers to the circumstances surrounding the death. There are generally five choices (some jurisdictions include more): natural, accident, suicide, homicide, or indeterminate.

Homicide is often described as “death at the hands of another or another”. Homicide is not necessarily criminal – homicides can be a matter of self-defense, for example. Courts, not forensic pathologists, determine criminal culpability.

In addition to the examination of the body, which usually occurs quickly, pathologists take into account other documents such as the police report, videos, medical records and toxicology reports, said Dr Priya Banerjee, board certified forensic pathologist. “We don’t practice in a black box,” she says. Until the full results of the investigation are known, she says, she generally says the case is awaiting further investigation.

In the vast majority of cases, the cause and manner of death are obvious, according to forensic pathologists. But in some situations, the professional opinions of well-trained and experienced experts may differ.

“Some cases are much more complicated than others,” said Dr Banerjee. When an “autopsy was not a slam dunk,” said Dr Banerjee, the written cause of death may be “more wordy because it takes into account many factors.”

This can happen when an autopsy does not reveal a fatal injury such as a gunshot wound to the brain. “Autopsies are good for showing demonstrable changes in body tissue,” said Dr. Christopher Happy, a certified medical examiner, “but they are not good for showing things that were functional, like seizure, depression. respiratory or arrhythmia. unless there is an injury associated with it.

Dr Baker described Mr Floyd’s cause of death as “cardiopulmonary arrest complicating the subdualization, restraint and compression of the neck”. The mode of death, he wrote, was homicide.

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The use of the term cardiopulmonary arrest has confused the public because some people have mistakenly assumed it to mean Mr. Floyd has had a heart attack. Cardiopulmonary arrest means that “the heart stops beating and the lungs stop moving,” said Dr Cyril Wecht.

Some pathologists say they don’t include it as a cause of death because it describes all deaths.

Dr Baker also detailed “other significant conditions” including pre-existing conditions such as severe disease of the vessels in Mr Floyd’s heart. He also described the lab results of fentanyl and methamphetamines, an opiate drug, in Mr. Floyd’s blood. Not including them under cause of death means he concluded that “these were there before but did not trigger the lethal sequence of events,” said Dr Melinek. Listing them “aims to clarify” what made Mr. Floyd more vulnerable to the cause of death, she said, “do not excuse him.”

Here, context matters. Dr Baker told prosecutors that if Mr Floyd had been ‘found dead alone at home’ without ‘any other apparent cause’, they wrote, it might have been acceptable to determine that Mr Floyd died of an overdose due to the levels of fentanyl found in his blood drawn at the hospital.

Instead, the recordings revealed both Mr Floyd’s prolonged restraint just before his death and also that he appeared restless rather than lethargic, which could suggest tolerance to higher doses of fentanyl. The drug “usually relaxes you,” said Dr Wecht.

In contrast, said Dr Melinek, defense attorneys for Mr Chauvin appear to be trying to use the medical findings to convince the jury that Mr Floyd “was essentially a ticking time bomb, already had pre-existing conditions which made this end point possible, not because excessive force was used. “

Simply claiming he was at a higher risk of dying under police duress due to underlying health conditions or drug use would likely be legally insufficient, some experts have said.

The medical examiner’s office had not completed its investigation when prosecutors filed a charge sheet saying preliminary findings showed no physical evidence to support a diagnosis of “traumatic asphyxia or strangulation.” He said the combined effects of the police restraint, underlying health issues including heart disease, and “all of the potential intoxicants in his system likely contributed to his death.”

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Forensic pathologists have said that in high-profile cases, it can be problematic to release results early because they may be misinterpreted or incomplete. “Basically, I never disclose the preliminary cause of death,” Dr Banerjee said.

After the initial autopsy, forensic scientists no longer have access to an intact body, and sometimes organs or tissues are unavailable, having been removed for further study. Even so, doctors sometimes document findings that an examiner missed during the first autopsy or that were not apparent.

“There are several reasons why you might see something on the second autopsy that was not seen on the first and vice versa,” said Dr Melinek.

Mr Floyd’s family hired Dr Michael Baden and Dr Allecia Wilson to perform a second autopsy. The two experts said the pressure on Mr Floyd’s neck and back during his restraint by the police had caused him to die of asphyxiation, a term Dr Baker did not use in his official report. .

The word asphyxia derives from an ancient Greek term meaning “without pulse”. Doctors now use it to refer to oxygen deprivation, which can occur for many reasons. At the center of the case is whether Mr. Chauvin’s actions led to any of them, such as inhibiting the movement of the diaphragm which allows the lungs to expand or reducing the flow of blood carrying l oxygen to vital tissues. Oxygen deprivation can come not only from compressing the neck, experts say, but also from pressure on the back when someone is lying on their stomach, and this may not leave any major physical marks.

According to some experts, the cause of death described both by Dr. Baker and by the pathologists who performed the second autopsy amounts to much the same thing, namely that “the external pressure while lying on Mr. Floyd caused his death. dead, ”said Dr Floyd. Banerjee said.

Shaila Dewan contribution to reports.


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