Chapter 13

Gasping for Air: Asphyxia

IN THIS CHAPTER

Understanding deaths by asphyxiation

Checking out causes and mechanisms of suffocation

Taking a look at strangulations and hangings

Sniffing out deadly gases

Dealing with drowning deaths

Ever attempt to hold your breath for two minutes? Try it. It’s not as easy as it sounds. Two minutes can seem like an eternity. Now, imagine that you can’t breathe. What if something prevented you from taking a breath or the air that you could breathe in had no oxygen or was laced with a toxic gas? What if the next breath never came? That’s asphyxia — when the body’s cells can’t get oxygen. It can happen in several different ways, each leaving a clue or two for the medical examiner (ME).

Understanding Asphyxia

The air we take into our lungs contains oxygen (O₂). After it’s in the lungs’ air sacs, the O₂ crosses into the blood, combines with the hemoglobin of the red blood cells, and travels with those red blood cells throughout the body.

Normal air contains approximately 21 percent oxygen. When this percentage drops to 10 to 15 percent, judgment and coordination suffer. You lose consciousness when the O₂ concentrations in the air fall below 10 percent, and death occurs at around 8 percent.

An interruption of the supply of O₂ at any step in its path from the environment to the cells of the body can lead to asphyxia. For example:

• Suffocation: The air may contain little or no O₂, or something (like a suffocating gas) may prevent that O₂ from reaching the bloodstream.
• Strangulation: A blockage or obstruction prevents air from entering the airways and the lungs.
• Drowning: The lungs fill with water, thus preventing oxygenation of the blood.
• Inhalation of toxic chemicals: Certain toxins can interfere with the uptake of O₂ by the blood or the cells’ use of oxygen in the body.

Gasping for Oxygen: Suffocation

You can’t see it, and you probably rarely think about it, but oxygen in the air keeps your body operating and your mind at its peak. Whenever you can’t get enough oxygen into your bloodstream, suffocation occurs. It may happen because the air has very little O₂ (at the top of Mt. Everest or in a tiny, air-tight, enclosed space) or because some object (a suffocating gas, for example, or a peanut that got stuck in your throat) keeps the O₂ from reaching the lungs and ultimately the bloodstream.

Suffocating environments

Deaths from environmental suffocation, which occur when someone cannot get sufficient oxygen from his surroundings (usually in a small space or one in which the air quality is poor), are most often accidental, but homicidal incidences are not unheard of. The classic example of an accidental death from environmental suffocation is a child trapped inside an old refrigerator. With no fresh air available, once the oxygen inside has been consumed, the child dies from asphyxia.

A determination of the cause and manner of death in an environmental suffocation relies on an analysis of the circumstances surrounding the death and on the fact that no other cause of death turned up at autopsy. In other words, if someone finds the victim in an oxygen-poor environment or an airtight enclosure with no evidence of trauma or toxin exposure (and if the medical examiner rules out natural causes), the ME may deem the death an accidental suffocation.

Smothering

Smothering occurs when some external device prevents air from entering the nose or mouth. You can distinguish smothering from choking (see the following section, “Choking sensations,” for more about that form of death) because, in smothering, the obstructing material is outside the mouth or throat.

Common examples of smothering include the following:

• Suicidal smothering usually employs a plastic bag, which the individual places over his head and secures with tape or a rope.
• Plastic bags may also account for accidental smothering, particularly in children. On rare occasions, an intoxicated individual can lose consciousness face down on a pillow and die from smothering.
• Homicidal smothering usually employs a pillow, bedding, plastic bag, or the killer’s own hands. When the killer uses a pillow or a plastic bag, the victim typically has no visible marks unless he struggles, in which case the victim’s face or arms may show abrasions or bruises left by the killer’s attempts to control the victim.

Choking sensations

Choking results when an obstruction occurs within the airways. The cause of death may be natural, homicidal, or accidental.

A natural choking death may result from an acute infection and inflammation of the epiglottis, which is the flap at the upper end of the trachea (main airway) that closes to prevent the aspiration of food and water when we swallow. With severe inflammation, the epiglottis can rapidly swell and block the airway. This is a true medical emergency and must be treated immediately, usually with a tracheostomy. This is an incision into the trachea below the larynx (Adam’s apple) that creates an alternate pathway for air to reach the lungs.

Diphtheria, which can cause a natural choking death, is now, thanks to widespread immunization programs, rare in the United States. Diphtheria is a bacterial infection of the throat that is associated with the formation of a thick, tenacious pseudomembrane that can peel away from the throat and obstruct the airway.

Homicidal choking deaths also are rare. However, if an assailant gags the victim by placing a sock, cloth, ball, or other object in the victim’s mouth before applying the gag, the victim may choke and die. As with deaths from smothering, if the choking device is not found in the victim’s mouth or near where the body is found, the ME may not be able to determine the exact cause of death.

Most choking deaths occur accidentally. Children get small objects, such as pieces of balloons, parts of toys, and food materials, into their airway and choke. With adults, the culprit is almost always food. In fact, choking to death on food occurs so commonly that physicians have given it the moniker “Café Coronary.” Typically, the victim is eating, suddenly stops talking, perhaps grabs her throat, and collapses. On the surface, it looks like a heart attack, or coronary. In reality, the airway is obstructed, the victim can’t breathe, the blood oxygen level drops dramatically, and the victim collapses and dies.

With natural and accidental choking deaths, the ME usually has little difficulty in determining the cause of death. However, finding food material within the victim’s airway does not absolutely indicate that the victim choked to death. Many individuals who are eating at the time of death suck food into their airways and lungs as they die. Investigators can take a detailed history of what actually happened from witnesses, giving the ME what may be the most useful information in determining the cause of death. If a piece of meat or other firm food product completely obstructs the airway, the ME may be able to state, on that evidence alone, that the victim indeed died from choking.

Applying pressure: Mechanical asphyxia

Mechanical asphyxia results when some external force applied to the body prevents the expansion of the chest and leaves the victim unable to breathe. A person trapped beneath a heavy object, such as a car or a collapsed wall or ceiling, can die because the force of the external pressure prevents the victim from taking in a breath.

A boa constrictor kills in exactly this way. This muscular species of snake wraps itself around its prey. Each time the prey exhales, the snake coils a little tighter. So, each successive breath becomes increasingly shallower until the prey can’t take another breath. Death follows quickly.

SUFFOCATION BY “BURKING”

Experts have come to know a particular form of mechanical suffocation as Burking. William Burke was a merchant of sorts around Edinburgh, Scotland, in the early 1800s. In 1827, he hooked up with William Hare, who ran a beggars hotel in the village of Tanners Close. In December of that year, a resident of the hotel died, and Burke arranged to sell the body to a Dr. Knox, who needed corpses for his dissection demonstrations. Burke and Hare loaded a coffin with bark and buried it in front of many witnesses. They then delivered the body to Dr. Knox and received seven pounds and ten shillings. The men struck an arrangement whereby Burke and Hare would deliver the doctor more bodies for eight pounds in summer and ten in winter. (Apparently grave robbing was more difficult when the ground was cold.)

Burke and Hare began digging up fresh corpses for their new enterprise, but the local populace refused to die fast enough for the greedy men. They began kidnapping and killing people who were not likely to be missed. Burke sat on his victims, holding their mouths and noses closed until they suffocated, after which Burke and Hare delivered the corpse and collected their fee.

A lodger at the hotel notified authorities when she discovered the sixteenth and last victim beneath a bed. Police arrested the two men. Hare then cut a deal and testified against Burke. Burke was convicted and experienced asphyxia for himself when he was hanged on January 28, 1829, an event attended by as many as 40,000 people.

Suffocating gases

Suffocating gases aren’t toxic or poisonous in and of themselves, but their presence diminishes the percentage of the oxygen in the air. Any gas added to air lowers the percentage of oxygen in the air. Room air contains approximately 21 percent oxygen. Whenever you add another gas to the air, it mixes with the gases already there, and the percentage of oxygen available drops in proportion to the amount of gas added. Oxygen levels below 15 percent can lead to lethargy, confusion, disorientation, and ultimately coma and death.

Carbon dioxide and methane are common examples of suffocating gases. Each is nontoxic and odorless. Methane is the principal component of natural gas. By law, an odor is added to household natural gas so that residents can detect leaks.

At autopsy, the ME rarely uncovers specific findings that prove the death was from suffocating gases. However, in methane-related deaths, the crime lab may find high levels of methane in the victim’s blood. Carbon dioxide is another story. Because carbon dioxide is normally found in our blood and the blood’s carbon dioxide levels often rise around the time of death, the ME may find determining the cause of death impossible when carbon dioxide is the culprit.

Grasping Strangulation

The next time you stand in front of a mirror, take a look at your neck. It’s not very big, is it? Yet, it’s basically the conduit of life: All communication between the brain and the body passes through the neck by way of the spinal cord, and all the brain’s blood supply from the heart must pass through the arteries of the neck. Thus, the neck provides a vital link between brain and body. But it’s exposed and vulnerable to injury, both accidental and intentional.

Strangulations are forms of asphyxia in which an outside force compresses the airways and blood vessels of the neck. This compression prevents blood from reaching the brain and air from entering the lungs.

Finding common threads in strangulations

The mechanism of death in most strangulations is cerebral hypoxia, which means a low level of oxygen in the brain. Strangulation blocks the airway, preventing the victim from breathing. It also prevents the flow of blood to the brain by blocking the carotid arteries, which pass from the aorta to the brain by way of the neck and are the major source of blood supply to the brain. In reality, most strangulation deaths are due to this interruption of blood supply rather than obstruction of air passage. And it can happen very quickly, a fact that is operative in many accidental strangulation deaths.

If you are inspired to feel around for your carotid arteries, be careful: Putting pressure on both carotid arteries at once can cause sudden death by activating a sensitive baroreceptor (pressure receptor) in the arteries that can induce a sudden drop in blood pressure and heart rate and lead to cardiac arrest.

Examiners often find petechial hemorrhages in all types of strangulation. Those hemorrhages are caused by blood leaking from ruptured capillaries and appear as small red dots or streaks in the whites of the eyes (sclera) and the pink parts around them (conjunctivae). These markings appear when the pressure within the veins of the neck rises suddenly and dramatically. This pressure transmits to the capillaries of the eyes, causing them to leak blood.

In many strangulation deaths, the victim’s face becomes congested. Fluid collects in the tissues, and the face appears swollen and often takes on a dusky hue.

Hands on: Manual strangulation

Manual strangulation occurs when someone applies pressure to the victim’s neck with a hand, forearm, or other limb, compressing the airway and the carotid arteries. The ME may be able to uncover any of several indications of manual strangulation:

• Contusions: The pressure from the assailant’s fingers and thumbs may leave bruises in the shape of fingers or, more often, round bruises that match the tips of the fingers and the pads of the thumb. The ME typically finds these bruises on the sides of the victim’s neck, but not always. If the assailant is facing the victim, he may use both hands and press his thumbs into the recesses where the carotid arteries lie. In this case, the major bruising appears on either side of the trachea (wind pipe), with smaller finger bruises on either side or the back of the victim’s neck.
• Abrasions: The assailant’s fingernails can cause abrasions on the victim’s skin. Because assailants tend to use the tips of their fingers to grip the victim’s neck, their nails may dig into or scratch the victim’s flesh. If the assailants’ nails aren’t closely clipped, abrasions may appear as linear scratches or as thin, semicircular or linear marks where the nails “dug into” the victim’s flesh.
• Injuries to the neck: Because most assailants use a great deal more force than they need to, they may cause injury to the neck muscles. The ME often finds bleeding in these muscles at autopsy. Also, the assailant often injures the small bones of the neck. Fractures of the cornu (horn) of the thyroid cartilage (Adam’s apple) and the tiny hyoid bone (a delicate C-shaped bone above the thyroid cartilage) often occur in manual assaults.

When the police locate a suspect, they need to examine the suspect carefully for signs of injury. Victims often put up a fight and scratch or bruise their attacker. The ME typically sees such injuries on the assailant’s fingers, hands, forearms, and face. If the attacker committed a rape-strangulation, the ME may find scratches along the attacker’s flanks or back.

Another form of manual strangulation is the chokehold, often employed by law enforcement officers to subdue a combative subject. The purpose of the chokehold is to collapse the carotid arteries and render the subject unconscious. Two forms exist:

• Bar arm hold: The officer places one forearm across the front of the subject’s throat and, using the other hand, grasps the wrist and pulls back, applying forearm pressure to the subject’s neck. The officer may use a baton rather than a forearm to apply the pressure.
• Carotid hold: The officer places the crook of one elbow against the center of the subject’s neck, and again grasps the wrist and pulls back. This produces a pincher or scissors effect, which occludes (blocks) the two carotid arteries.

Both of these maneuvers are dangerous and should never be performed by anyone who has not been trained to use them. The unconsciousness is caused by a restriction of blood flow to the brain, which, if applied too aggressively for too long, can lead to death or permanent brain injury. Police officers use these holds as a last resort to restrain extremely violent or uncontrollable people.

The ME often becomes involved in situations where these holds have been used and a police brutality complaint is filed. If too much force is used, the thyroid cartilage and the hyoid can fracture, and bleeding can occur in the strap muscles of the neck. In either a living or deceased subject, the ME must evaluate the injuries and develop an opinion.

Applying a ligature

Ligature strangulation occurs when someone tightens a constricting band around the neck. The tightening comes from some force other than the victim’s own body weight, as occurs in hanging (see the following section, “Hangings,” for an explanation of the difference). Essentially all ligature strangulations are homicides.

If the ligature is soft, such as a towel or bed sheet, it may not leave marks on the neck, though some bruising is not uncommon. A thin ligature, such as an electrical cord, leaves a deep groove or furrow in the tissue of the victim’s neck. This furrow’s deep impression matches the width of the particular ligature used. Not uncommonly, the ME sees associated bruises and abrasions on the victim’s neck. How many of these bruises and abrasions occur and how prominent they are depend on how fiercely and successfully the victim struggles against the attacker. Occasionally, these associated abrasions and bruises reveal the pattern of the ligature used.

Even in severely decomposed corpses, the ligature mark can be preserved. Apparently, the severe compression of the tissues within the furrow closes off the blood vessels underneath. The bacteria that cause a body to decompose tend to migrate through the blood vessels after death. Because the vessels in the furrow have been damaged and bacteria can’t pass easily through them, the number of bacteria that reach the area lessens, and thus the putrefaction process within the furrow slows.

The ligature furrow in ligature strangulations tends to be directed horizontally around the neck. Whether the assailant is facing the victim or approaching from behind, the ligature is tightened by pulling laterally on its ends.

At autopsy, the ME examines the victim’s hands and nails since hair clutched in the victim’s hand and blood and tissue from the assailant beneath the fingernails may be found.

Suicide by ligature strangulation is rare, but it’s not unheard of. Because loss of consciousness in ligature strangulations is predominantly due to carotid compression, it can arrive quickly, often in as little as 15 seconds. But, this still gives the victim time to secure the ligature in place by either tying a knot or by wrapping the cord around several times, the overlapping loops securing the ligature in place.

Accidental ligature strangulation is also rare. It typically occurs when a scarf, tie, or other article of clothing becomes entangled in a piece of machinery or a moving vehicle. These accidents often involve ski lifts, elevators, motorcycles, or cars.

ISADORA DUNCAN’S FAMOUS SCARF

Isadora Duncan was famous, an icon in the dance world, and is credited with inventing modern dance. She was also known for the long silk scarves she was fond of wearing. This fashion statement led to her death when, on September 14, 1927, in Nice, France, her scarf became entangled in the wheels of a moving convertible sports car (rumored to be a Bugatti), strangling her.

Hangings

In hangings, asphyxia results from the compression of the airways and the carotid arteries by a noose or other ligature pulled tight by the body’s weight. Thus, the victim must be completely or partially suspended. Hangings are almost always suicidal. Most accidental hangings occur in children when they find themselves tangled in a rope or clothing and in a position of complete or partial suspension.

Though hanging compresses the airway and interrupts breathing, the real cause of death in most hangings is compression of the carotid arteries, which blocks blood flow to the brain. Fractures of the cervical vertebrae (spinal bones of the neck) happen rarely in hanging deaths, except in judicial hangings, because these fractures require that the body drop a sufficient distance to break them.

In cases of death by hanging, the ME is likely to find the following evidence:

• Neck markings: The neck markings that you see after a hanging depend mainly on the nature of the noose used. Soft nooses, such as sheets, may leave little or no markings. A rope or cord may leave a very deep, distinct furrow in the victim’s neck. The longer the body hangs, the deeper the furrow.
• Furrow pattern: In hangings, the furrow has an inverted V pattern. The furrow tends to run diagonally across the neck with its high end at the knot.
• Facial changes: If found several hours after the hanging, the victim’s face may be pale, and the tongue may be dark purple and protrude from the mouth. At autopsy, the ME doesn’t usually find facial congestion or petechial hemorrhages (see the section “Finding common threads in strangulations,” earlier in this chapter, for the details on these reactions) that commonly appear in manual and ligature strangulations.
• Lividity: If lividity appears, it does so in the legs, forearms, and hands. Check out Chapter 11 for more about lividity.

• Drugs or alcohol: The ME should perform a toxicological analysis on all victims of hanging. An assailant may have used drugs or alcohol to subdue the victim in a homicidal hanging, and a suicide victim may have taken alcohol or drugs in order to get the courage to do himself in.

  Here, the ME may be able to determine whether the level of drugs and alcohol found in the victim was enough to knock him out or merely enough to impair his judgment. In most cases, making this call isn’t easy.

DYING FOR PLEASURE: AUTOEROTIC ASPHYXIA

Some people are willing to die for a good time. Autoerotic or sexual asphyxia, in which a person (usually a male) combines strangulation and masturbation, is proof positive.

These misguided adventurers bank on the idea that partial asphyxia somehow accentuates sexual enjoyment. One of the first symptoms of cerebral hypoxia (low oxygen in the brain) is giddiness, and the people who perform this act believe that this sensation accentuates sexual arousal.

Most often, hanging is the method of choice, but nonhanging ligatures and plastic bags also have been used. The victim rigs up a situation where the rope or chosen ligature compresses the neck on demand. This method of masturbation often involves some form of self-rescue device. The victim may be able to move a certain way to relieve pressure or have an instrument with which to cut a ligature or slice open a bag.

Unfortunately, miscalculations can lead to tragedy. Cerebral hypoxia causes poor judgment and coordination, poor assessment of the level of hypoxia, and sudden loss of consciousness. Once unconsciousness occurs, the victim can’t save himself.

Officials typically find a male victim, partially suspended by a hanging noose. At times, his hands are bound, which brings up the possibility of a homicide staged to look like an accidental death. But the victim may have used such binding as part of the ritual. An examination of the bindings may reveal whether the victim could have bound himself or not.

Inhaling Deadly Air: Toxic Gases

Here’s a terrifying thought for you: The very air you breathe can kill you. Chances are good that it never will, but if ever you encounter a toxic gas, breathing becomes not a life-giving but a life-taking exercise.

Toxic gases wreak havoc not by keeping oxygen from entering your lungs and bloodstream (as suffocating gases do) but by keeping your blood or body tissues from making use of that oxygen. Carbon monoxide (CO), cyanide, and the combination of hydrogen sulfide, CO, and methane (known as sewer gas) are common toxic gases.

That sneaky carbon monoxide

Carbon monoxide is sneaky and deadly. When authorities find a suicide victim in her garage, sitting in a car with the engine running, they can usually chalk up that death to carbon monoxide.

Carbon monoxide is a tasteless, odorless, colorless gas that is completely undetectable by humans. It results from the incomplete combustion of carbon-containing fuels like wood, coal, and gas. Faulty stoves, heaters, and fireplaces can fill the air with CO. Carbon monoxide poisoning kills more people trapped in fires than the fire itself does.

CO is particularly treacherous because it binds to hemoglobin, producing carboxyhemoglobin in your blood. Because carboxyhemoglobin contains no usable oxygen, cells containing this molecule can’t supply oxygen to the tissues of the body. Thus, the body’s cells become starved for oxygen. Carbon monoxide binds to hemoglobin 300 times more readily than oxygen does and thus takes oxygen’s place in the body. Your body can get very high blood levels of CO by breathing air that contains only small amounts of it. For example, breathing air that contains a carbon monoxide level as low as 0.2 percent can lead to blood CO saturations greater than 60 percent after only 30 to 45 minutes.

Most people believe that CO is toxic only in an enclosed area, but that’s just not true. People have died while working on their cars in the open air; typically, someone finds the victim lying near the car’s exhaust. Similarly, swimmers and water skiers who loiter near the dive platform on the back of an idling powerboat also run the risk of CO poisoning. Carbon monoxide’s powerful attraction to hemoglobin explains how people can succumb to CO poisoning in open areas.

The signs and symptoms of CO toxicity correlate with its concentration in the blood:

• The normal level of CO in the blood is 1 to 3 percent, but it can be as high as 7 to 10 percent in smokers.
• At levels of 10 to 20 percent, you experience headaches and a poor ability to concentrate on complex tasks.
• Between 30 and 40 percent, headaches become severe and throbbing, and nausea, vomiting, faintness, and lethargy appear. Pulse and breathing rate increase noticeably.
• Between 40 and 60 percent, the victim becomes confused, disoriented, weak, and displays extremely poor coordination.
• Above 60 percent, coma and death arrive.

In the elderly and those individuals with heart or lung disease, levels as low as 20 percent can be lethal. Victims of car exhaust suicide or those who die from fire in an enclosed room may reach CO levels as high as 90 percent.

Autopsy findings in CO poisoning depend, in part, on carboxyhemoglobin’s bright red color. When the ME performs an autopsy on a victim of CO poisoning, the blood and internal organs often appear bright red, and this offers a clue to the possible cause of death.

Individuals who survive CO intoxication can suffer serious health problems. Carbon monoxide mostly damages the brain because it’s the organ most sensitive to a lack of oxygen. Symptoms and signs of significant brain insult may begin immediately or be delayed for several days or weeks. The most common after-effects include chronic headaches, memory loss, blindness, confusion, disorientation, poor coordination, and hallucinations. The ME may be asked to evaluate a surviving victim if authorities suspect that the exposure was the result of a criminal act or they want documentation for a civil lawsuit.

Deadly cyanide

I’m sure you’ve read books and seen movies in which some nasty character uses cyanide to commit murder. In fact, few people use cyanide as a murder device. More people use it for suicide, particularly mass suicides. Individual and group accidental poisoning can occur in industrial settings. Technicians use cyanide salts in metal electroplating, jewelry making, and X-ray recovery industries. The plastic manufacturing industry uses solvents called nitriles, which contain cyanide. When burned, these nitriles can release deadly hydrogen cyanide gas.

JIM JONES AND THE PEOPLE’S TEMPLE

Jim Jones was a fundamentalist Christian pastor who established his People’s Temple in the 1950s in Indianapolis, Indiana, before relocating to the San Francisco area. Because of his claims that he could cure cancer, heart disease, and other maladies, he drew scrutiny and criticism. When suspicions arose about many of Jones’s financial dealings, he moved his followers from the United States to the makeshift town of Jonestown, Guyana.

Rumors of human rights abuses followed him and attracted the attention of some members of the U.S. Congress. In 1978, Congressman Leo Ryan and members of the press visited Jonestown and talked with many of the People’s Temple members, 16 of whom asked to leave with the Congressman and return to the United States. As the departing members and Congressman Ryan awaited a plane at Port Kiatuma Airport, they were ambushed by several of the Temple’s security guards. Congressman Ryan and four others were killed, and 11 people were wounded.

Soon after that incident, Jones fed his congregation a fruit drink laced with cyanide and the sedatives Valium and chloral hydrate. More than 900 people died, including more than 250 children. Toxicological testing of the drink and of fluids taken from the deceased proved that cyanide was the culprit.

Hydrogen cyanide gas is the most deadly form of cyanide. Ingesting cyanide salts such as sodium and potassium cyanide produces hydrogen cyanide gas when those powders react with the acids in the stomach. Gas chamber executions use hydrogen cyanide.

Cyanide is a deadly metabolic poison, which means that it prevents the body’s cells from using oxygen, thus causing the cells to die rapidly. The body acts as if all the oxygen had been suddenly removed. The oxygen is still there, of course, but the cells can’t use it. And because the cells no longer extract the needed oxygen from the blood, the blood remains very well oxygenated (rich in oxyhemoglobin) and thus bright red.

At autopsy, the ME can see that the blood of the victim is bright red and not the expected dark purple, thus suspecting cyanide or carbon monoxide as the cause of death. Also, any lividity may be pinkish, rather than the usual blue-gray hue, which likewise suggests cyanide or CO poisoning. In addition, the ME may detect the typical bitter almond odor of hydrogen cyanide — that is, if he is capable. Curiously, the ability to detect this odor is genetically determined. Some people can while others can’t.

Getting down with sewer gas

Hydrogen sulfide is a byproduct of fermentation and is typically found in sewers and cesspools. Chemists call the combination of hydrogen sulfide, carbon monoxide, and methane sewer gas. When you inhale this sewer gas, the hydrogen sulfide takes oxygen’s seat on your hemoglobin (much like carbon monoxide does, which I describe in the earlier section “That sneaky carbon monoxide”), and your cells can’t get the oxygen they need. Hemoglobin with this gas attached adds a dark purple color to the blood. Sewer gas deaths are almost always accidental and occur when the victim enters an area rich in sewer gas and succumbs to the hydrogen sulfide. At autopsy, the ME finds high levels of sulfide in the victim’s blood.

Drowning: Water, Water Everywhere

Drowning is a common fear and a decidedly unpleasant way to go. As you drown, your lungs fill with water, and they lose their ability to transfer oxygen into the bloodstream. While you struggle to breathe, you force water into your sinuses. Coughing triggers an inhalation reflex, which pulls even more water into the lungs. The loss of an air supply combines with the energy you consume in the struggle for survival, and the oxygen level in the blood rapidly falls. You lose consciousness in one to two minutes. The heart stops shortly thereafter.

Finding the manner of death

Drowning is almost always accidental. But MEs often have a difficult time determining the manner of death. Indeed, concluding that the victim actually drowned mostly comes as a diagnosis of exclusion, meaning that the ME starts by determining what didn’t happen.

The circumstances of the death are often more important than any physical findings. If the ME can’t find any evidence of trauma or natural disease to explain the death, and if the victim is found in water, the ME may determine that the death was from drowning. No pathological findings at autopsy can definitely say one way or the other.

Even the finding of pulmonary edema (water-filled lungs) doesn’t prove drowning because pulmonary edema can occur with deaths from heart attacks and some drug overdoses. If a victim died from a drug overdose and was dumped into water or the person suffered a heart attack and developed severe secondary pulmonary edema (water in the lungs arises when a failing heart causes increased pressure in the lung vessels), the autopsy findings may look identical to those of someone who truly drowned. For this reason, the ME should perform a complete toxicological analysis on all suspected drowning victims.

Experts once believed that a classic finding in victims of drowning was a thick, white, or blood-tinged foam in the mouth, throat, and trachea. However, this finding has little evidence to support it, so most modern investigators have dismissed it.

Diving deeper to identify drownings

Drownings are a complicated business for the ME. In fact, the ME may not be able to determine whether the victim was dead or alive when he entered the water. If you place a corpse in water, and it remains submerged for a period of time after death, the lungs passively fill with water, and the ME’s examination can’t distinguish this postmortem fluid in the lungs from liquid that resulted in death.

As many as 15 percent of drownings can be dry drownings. In this situation, the intake of water into the throat causes laryngeal spasm. The larynx reacts to the water by spasming (constricting or closing). This reaction shuts down the passage of air into the lungs, and the victim asphyxiates. This spasm also prevents water from entering the lungs, so the lungs are dry at autopsy.

But the ME has a few tricks to help him. Finding some or all of the following evidence points the investigation in the direction of drowning:

• Hemorrhaging: If a conscious victim enters the water, the struggle to breathe causes a great deal of pressure trauma to the sinuses and the lungs. The ME expects to find hemorrhaging (bleeding) into the sinuses and airways, as well as debris from the water, which the victim sucks into the sinuses and lungs while attempting to breathe.
• Souvenirs from the sea: Plants or rocks from the bottom of the body of water clutched in the victim’s hand may indicate that the victim grabbed them during the struggle to survive. Sort of like grasping for straws.

• Tiny invaders in the bone marrow: Though controversial, a search for diatoms may indicate whether the victim was alive or not at the time he entered the water. Diatoms are tiny, single-celled organisms that scurry around in salt water and fresh water (diatoms also turn up in many fire investigations — turn to Chapter 8 to find out more). They have silica in their cell walls and are thus very resistant to degradation.

  Until cardiac action ceases, any inhaled diatoms pass through the lungs, enter the bloodstream, and are pumped throughout the body. They tend to collect in the bone marrow. Microscopic analysis of the marrow can reveal diatoms, meaning the victim was alive after entering the water, instead of being placed there after death. Because these diatoms are so hardy, this technique is useful for evaluating severely degraded and even skeletal remains, where no lung or sinus tissues are available for examination.