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Drowning investigations.

On a lake in Missouri, investigators made a grisly discovery. They found a white male floating with a heavy boat anchor attached to him with a rope. The subsequent autopsy revealed that someone killed him and dumped his body into the water. Eventually, authorities arrested a suspect who later was convicted of murder.


Another case involved a man who was accidentally ejected from a boat traveling at a high rate of speed on a Missouri lake. Apparently, he hit his head, became unconscious, and drowned, disappearing below the surface of the water. The incident occurred in the main channel of the lake, which measured over .5 mile wide and varied from 70 to 110 feet deep. A witness could not closely identify the location of the accident, hampering investigators' attempts to locate the victim. To further complicate matters, the area had a substantial amount of underwater timber that remained from before the formation of the lake. Authorities made numerous attempts to recover the man's body by dragging, scuba diving, and using canines--all of these methods proved unsuccessful. Five years later, the remains of a decomposed foot wearing a sock and a tennis shoe surfaced and began floating in the approximate area of the lake where the man's body disappeared. Authorities identified the sneaker as the one worn by the victim before the accident. Decay was well advanced, and the joint at the ankle had completely rotted away, allowing the foot to float free from the body. Although most corpses come to the surface during the decomposition process, this case probably represented one of the rare instances in which a body remains entangled in some type of underwater obstruction, such as timber or brush.

Law enforcement personnel conduct a large number of drowning investigations. Some involve homicides or suicides, but most result from accidents. Drowning represents the fourth leading cause of accidental death in the United States, with between 4,000 and 5,000 incidents occurring annually. (1) This number alone indicates that many police officers, in the marine environment and otherwise, will routinely investigate drowning deaths. Agencies need to ensure that their personnel remain well prepared to handle these cases when they arise.



Drowning refers to death due to submersion in a liquid--as shallow as 6 inches in cases involving infants, the elderly, people afflicted with epilepsy, or individuals under the influence of alcohol or other drugs. Irreversible cerebral anoxia, or lowered oxygen to the brain, due to asphyxiation serves as the mechanism of death. (2)

Experiments conducted in the late 1940s and early 1950s suggested that many drowning deaths resulted from electrolyte disturbances or cardiac arrhythmia produced by high volumes of water entering the circulatory system through the lungs. However, present thought considers hypoxemia, or deprivation of oxygen to the systems of the body, the most important physiological consequence of drowning. Also contrasting previously held theories, recent research suggested that the heart and kidneys can compensate for large amounts of water absorbed by the lungs. In near-drowning cases, physicians have not observed the electrolyte changes previously thought to occur. This information should not discount the possibility of cardiac irregularities due to the inundation of the circulatory system when an individual absorbs large volumes of water; this heart-related stress can contribute to death. (3)


Experts consider some individuals who drown as victims of dry drowning. In these cases, the fatal cerebral hypoxia, or oxygen deprivation, does not result from water occluding the airway but, rather, from a spasm of the larynx. Water never enters the lungs. These instances constitute 10 to 15 percent of all drownings.

When people sink beneath the surface of the water, they initially react by holding their breath. This continues until they have to breathe, thereby involuntarily inhaling a large volume of water, which either enters the lungs (in most instances) or reaches the larynx--producing the laryngeal spasm that results in dry drowning. In both cases, this gasping for air may continue for several minutes until respiration ceases. Cerebral hypoxia will progress until it becomes irreversible and death occurs. (4)

The point at which a person dies depends largely on the age of the victim and the temperature of the water--if warm, somewhere between 3 and 10 minutes. Some rare situations involving submersion of children in extremely cold water (less than 40[degrees]F) have resulted in successful resuscitation with complete recovery after longer periods of time, the longest being 66 minutes. Such cases probably result from the more rapid development of hypothermia in children. Most commonly, people lose consciousness within 3 minutes of submersion. Also, recent research has indicated that the type of water inhaled, whether fresh or salt, probably has very little influence on whether the individual will survive if resuscitation is initiated.

Death by cardiac arrest, rather than by drowning, presents another possibility when individuals become suddenly and unexpectedly submersed in cold water or overexerted. Additionally, uncontrollable respiratory distress due to cold water immersion may cause the victim to inhale water, and investigators may falsely suspect drowning.

The Body in Water

The human body weighs slightly more than fresh water. Consequently, when individuals become unconscious, they sink--regardless of fat level, which slightly increases buoyancy. Generally, a drowning victim will reach the bottom of a body of water in spite of the depth, unless it meets some obstruction on the way down. As the corpse descends further, the pressure of the water tends to compress gases in the abdominal wall and chest cavities. As a result, the body displaces less water as it sinks and, consequently, becomes less buoyant the further down it goes, until it reaches the bottom. (5)

If a corpse does not sink, investigators should suspect another cause of death, such as heart attack. Or, perhaps, a dry drowning has occurred; in those cases, because the lungs do not contain water, the body will not descend.

Almost without exception, a corpse lying on the bottom of a lake or river eventually will surface because of the gas formed in its tissues as a result of decay and the action of internal bacteria. This results in reduced specific gravity of the body so that it rises. Witnesses to this event have described corpses breaking the surface of the water with force, like the popping of a cork.

Factors that effect the length of time for a body to surface after drowning include fat content, consumption of beverages and food preceding death, water temperature at the bottom, and depth at the location. Recent meals high in carbohydrates (e.g., candy, beer, and potato chips) nourish certain bacteria that will encourage quick refloat. (6) In warm and shallow water, the gases within the body form rapidly, resulting in a possible rise to the surface within a day or two. In deep and cold water, bacterial action takes place slowly, and the corpse may not appear for several weeks. (7) When the body becomes greatly distended with gas, the tendency to float increases. Many well-documented cases exist of homicide victims dumped into lakes and rivers and then later surfacing, even though perpetrators attached heavy weights to them.

In some cases, the body may remain immersed. Extremely deep, cold water conditions (e.g., natural glacier lakes, deep impoundments) may prevent a corpse from ever becoming buoyant enough to overcome the immense water pressure.

Rivers and the Effects of Currents

Rivers differ from other bodies of water in two ways--they are shallow and have currents. Depths of less than 10 feet do not have a high level of compression on the internal air spaces of drowning victims.

In extremely heavy currents, such as in flash-flood situations, the victim's body probably will roll on the bottom for a considerable distance--trees or other debris also may carry along the corpse. During normal conditions in most rivers, this is not the case, and investigators usually will find victims on the bottom relatively close to the drowning site. However, after the body floats to the surface, it may drift due to the current before washing ashore or coming to rest in a back eddy. (8)

Lakes and the Depth Factor

Victims who drown in lakes will sink to the bottom in the area below the point of submergence; authorities usually will locate the body within a radius equal to the depth of the water. However, witness error can come into play. Even when someone sees the incident, authorities may find establishing the site difficult or impossible if the victim drowned far from shore. Because of panic and anxiety, people usually do not think to mark the location where the individual went down or to note nearby landmarks, thereby eliminating triangulation as an option. Investigators find it hard to locate drowned victims in lakes unless the incident occurred near the shoreline, from an anchored boat, or at a dock secured to the shore. This problem becomes further complicated in deep and dingy water, which may eliminate any possibility of recovery attempts by scuba divers. Often, waiting for the body to float to the surface becomes the only viable option.


Lakes rarely have a current strong enough to affect a body sinking or surfacing. However, the victim likely will move after refloat, and wind can push corpses. In lakes, the effect of even slight wind movement easily can offset any current that might exist.

Often, especially in the summer months, lakes have definite thermoclines--two layers of water at different temperatures. While the surface can measure 75 to 90[degrees]F, the temperature can drop 20 to 30[degrees]F at a depth of 40 feet--this cold water will tend to retard the reflotation process. (9) A myth exists that a drowning victim can become suspended on a thermocline because of the difference in water density between these two layers. However, no known case exists of this happening; in fact, internal air compression on descent and expansion on ascent make this virtually impossible. (10)


Investigators can look for some distinctive signs to determine cases of drowning. Officers must recognize these indicators and then articulate them to the medical examiner. Presently, no known and proven pathological test exists to determine drowning as the cause of death, so, by itself, an autopsy usually proves insufficient. Authorities can make this diagnosis only with a knowledge of the circumstances and exclusion of other causes.

Investigators need to answer several questions in apparent drowning cases. For instance, did the person drown, or did perpetrators kill the individual and dispose of the corpse in the water? Was the victim conscious upon submersion? Could the person swim well? Did the victim consume any alcohol or drugs? What was the individual doing at the time? Did anyone witness the incident? If any injuries exist on the body, were they caused before death (antemortem), at the same time (agonal), or afterwards (postmortem)? In the course of their investigation, authorities will find that a combination of external signs will provide valuable information. (11)

Bodily Substances

Investigators should look carefully around the victim's head, face, and mouth for any signs of vomitus. They should make this observation first as this very transient evidence easily can wash away. Presence of vomit serves as a reliable indicator that the victim became submerged while alive.

Foam often exudes from the nose or mouth of victims of wet drownings. This froth results from a mix of mucous, air, and water during respiration. Its presence serves as an indication that the person became immersed while still breathing, although authorities do not consider it conclusive evidence that the individual drowned. Some blood resulting from the tearing of lung tissue by forceful breathing just prior to unconsciousness may exist with it. Investigators should note that decomposition can destroy the foam. (12) This froth is similar to that often found on individuals who have died from acute heart failure or a drug overdose, both of which usually result in massive pulmonary edema. (13)

Transient in nature, this frothy foam easily can wash away during recovery operations. Sometimes, it may continue to ooze from the nose and mouth for a period of time after recovery. In other cases, no visible signs of it may exist, even in confirmed drownings. The lack of a froth cone is more typical when the victim did not fight the drowning process and gasp forcibly for air when disappearing below the surface of the water (e.g., intoxicated or unconscious individuals).

Adipocere refers to a fatty wax substance that forms on bodies either submerged in water or buried in damp conditions without oxygen and air. Its presence on a corpse recovered from water indicates that the victim probably has been there for a long time.


Investigators normally will find postmortem lividity, or blood pooling, on the portion of the body or head lying on the bottom after drowning. For instance, a corpse that ends up face down should have this condition evident on the chest, abdomen, face, or all of those areas. Typically, lividity is most evident in the head or neck because the body normally assumes a position of head down, buttocks up, and extremities dangling downward. Blood pooling not conforming to these patterns should alert authorities to investigate further to determine if death preceded immersion.


A drowning victim's eyes provide a ready, easily accessible, and useful source of information relating to the cause and time of death. As this evidence also is transient in nature, investigators need to note it immediately after recovery.

If death occurred on land, a noticeable horizontal line should exist on the eyeball if, as is common, the eyelids remained partially open, thereby allowing exposure to air and its drying effects. The line, or border, between the clear and cloudy cornea--the raised, usually clear area of the eyeball covering the pupil and iris--and the white and discolored sclera--the opaque, normally white portion--will occur only in these instances.

Conversely, if the victim drowned and is submerged in water at the time of death, then the eyes will retain a lifelike, glistening appearance. No lines will be present. (14)


The skin on the hands and feet of a body will have a wrinkled "washerwoman" appearance if immersed for more than 1 or 2 hours. This is called maceration and does not indicate that the deceased has drowned as it will develop whether the individual was alive or dead when entering the water. After prolonged immersion, the outer layer of skin may become completely separated from the feet and hands and come off in a glove or sock fashion. Investigators can obtain fingerprints from the intact or detached skin, which retains the same ridge pattern.


Rigor mortis, or postmortem rigidity, results from a chemical reaction that commences at death. It usually begins to develop within 2 hours, becoming fully established in 6 to 12. Rigor mortis results from muscle rigidity, not a stiffening of the joints. Once fully established, it remains for a variable period of time and then gradually diminishes (24 to 36 hours after death). Both the onset and disappearance of rigor mortis will vary depending on water temperature. Investigators should note that cold water can retard the process. (15) Also, it may be poorly formed in infants and elderly persons.


When initially recovered from the water, portions of the body--mainly hands and arms--may appear to be in full rigor mortis, even though only a short time has passed since death occurred. This phenomenon, cadaveric spasm, results from the typically violent struggling of an individual at the time of the drowning. Cadaveric spasm forms only under conditions of extreme mental stress and indicates the victim's last thoughts and actions. It occurs virtually instantly and only in groups of voluntary muscles, unlike rigor mortis, which progresses evenly throughout the body at a steady rate. (16)

Another condition, cutis anserina, or goose flesh, is a spasm of the erector pilae muscles due to rigor mortis. It does not indicate whether the person was alive or dead while entering the water.


Putrefaction refers to the decomposition of the body because of bacteria and fermentation. Although this process can take longer in water-submerged victims, these individuals may remain concealed longer when they become hidden in water or vegetation or lost in a large body of water; this results in correspondingly advanced postmortem changes before recovery. No time schedule for the stages of decomposition exists as differing water and climatic conditions will have a profound effect. Generally, cold and swiftly moving water preserves bodies, whereas heavy clothing and stagnant, warm water hasten decomposition.

The sequence of events remains relatively constant. Skin maceration begins, followed by progressive bloating and discoloration. The abdomen becomes greenish or purple; it also becomes distended because the body cavity fills with gas. Skin and hair detach and the tongue and eyes protrude. Features swell until authorities find victim identification difficult. Advanced stages of putrefaction can lead to mummification of the skin, especially if the body refloats, becomes exposed to the drying effects of air, and remains hidden for a long time.

Body Posture

Corpses normally exhibit a relaxed, often prone, semifetal position when discovered by divers on the bottom of a body of water. They assume this posture because of the buoyant properties of water; the natural forces exerted by the skeletal muscles, even when relaxed; and the buoyancy of the lungs, which lie nearer the back than the front. In this position, the arms and legs usually are slightly bent at the elbows and knees. The head often tilts slightly forward, and the spine curves slightly. Authorities should see this configuration upon recovery when rigor mortis is developed.

Any person who has died on land and remained in a terrestrial environment during the onset of rigor mortis will display a different posture. The head likely will be rotated to one side, a position almost never found in a drowning victim. (17)

Hand and Arm Positions

Investigators often will find a drowning victim's arms bent with the hands turned toward the face when rigor mortis has developed. In those cases, it appears that individuals tried to cover their mouths to prevent drowning. Often, they clinch their hands in a fist. These arm and hand positions are much less pronounced or not present at all in victims who drowned while intoxicated because these individuals generally do not struggle, but simply disappear below the surface of the water.

Sometimes, investigators may find objects in the hands of victims, such as grass from an embankment. If the drowning occurred in relatively shallow water, soil or gravel commonly found on the bottom may be clutched in the hands, indicating that the individual probably entered the water while conscious. (18)

Injuries and Marks

Immersion of a body in water for several hours may cause leaching of blood from injuries, such as propellor cuts, lacerations, and stab wounds. Thus, an individual may have a number of what appear to be bloodless postmortem injuries, which actually are antemortem or agonal and the cause of the person's demise. Of course, all recovered bodies need careful inspection for possible antemortem injuries. Because of the leaching effect, investigators may find detecting these wounds difficult.

Severe antemortem or agonal injuries usually will leave definite signs, such as bruising and dispersing of blood into adjoining tissues, because the heart still was pumping blood when these wounds occurred. This appearance will diminish as putrefaction progresses.

Legitimate postmortem injuries can occur to a body, especially around the head, face, knees, tops of the feet, and backs of the hands, although investigators should take care not to confuse these with defense wounds. A corpse that floats to the surface after partially decomposing is subject to currents that can repeatedly drag it across rocks and obstructions. In a very strong current, the body can travel far underwater, also causing these postmortem injuries.

In addition, marine life can cause postmortem damage to a body. It is not unusual for the lips, ears, and nose to be at least partially eaten away.

Boat propellers also can cause postmortem injuries, especially to a body that floats back to the surface at night and then gets hit by a motorboat before discovery. Investigators must differentiate postmortem propellor cuts from antemortem or agonal ones; in most instances, corpses refloat facedown, so those that occur after death nearly always will be to the back and shoulders, back of the head, or buttocks.

Medical examiners can help draw conclusions about the actual nature of wounds detected. But, investigators must provide all pertinent details.


Over the years, experts have developed and tried a number of tests to determine conclusively whether a person drowned. All have proven unreliable on their own. No morphologic findings diagnostic of drowning exist. Although an autopsy usually is not sufficient by itself, it can exclude other possible causes of death. (19)

Coroners will find the lungs of the typical wet drowning victim large and bulky, completely occupying their respective cavities, with a brick red appearance and large quantities of foamy edema. White foam commonly exists in the trachea and bronchi. The stomach may contain water. There may be dilation of the right ventricle of the heart due to absorption of large quantities of water into the circulatory system.

Examiners may find swelling in the brain and hemorrhaging in the petrous or mastoid bones. Authorities also may encounter these symptoms in people who died of heart disease, abuse of substances, or other causes. Thus, the drug overdose victim dumped in a lake and the heart attack victim collapsing into the water can have the washerwoman and goose flesh appearance, pulmonary edema, and hemorrhage into the petrous and mastoid bones. This demonstrates for investigators the importance of gathering other information to assist medical examiners in determining the proper cause of death when drowning is suspected. (20)

Once water has flooded the lungs, osmosis may cause a portion of any alcohol in the blood to pass out of the circulatory system into the flooded alveoli. When this occurs, the possibility exists that the resultant postmortem blood alcohol analysis may measure as much as 30 percent less than before death. (21)


Through a U.S. Department of Homeland Security grant obtained in the spring of 2004, the Missouri State Water Patrol received money to purchase sophisticated side-scan sonar equipment capable of finding underwater bombs, improvised explosives, and other devices that could pose a risk to bridges, dams, and other structures. Fortunately, it also can locate a human body on the bottom of a lake or river. This technology is far superior to conventional paper or liquid crystal graphs. On a computer monitor, it can paint an accurate picture of the bottom of a waterway and effectively eliminate from consideration large sections of water during a search for bombs, vehicles, planes, evidence, or bodies.

This side-scan sonar equipment has greatly improved the recovery rate of drowning victims in various Missouri waterways. It also has enhanced the efforts of the scuba divers of the Missouri State Water Patrol Underwater Recovery Team. Those personnel now can dedicate their limited air and bottom time to potential targets located by the sophisticated equipment. This technology has successfully found victims in large search areas, even in incidents without a witness or when excited individuals did not precisely note the location of the drowning. The use of the side-scan sonar has resulted in the recovery of victims that otherwise may have remained missing without refloating to the surface.


Law enforcement agencies deal with thousands of drowning investigations per year. Officers need to be aware of the unique nature of these incidents. Investigators should not assume that an autopsy will establish cause of death; they need to ascertain as much information as possible at the scene. Then, they must provide these important details to the coroner.

The investigator's role in a drowning investigation is crucial to a medical examiner in establishing an accurate cause of death. The officer must treat a drowning like any other death investigation and help to make sure it is conducted thoroughly and professionally. Then, the investigator can have confidence in the proper determination of cause of death and, if necessary, will be prepared to pursue the investigation further.


(1) The author based this approximate figure on his professional experience and research. For additional information, visit the Web sites of the Centers for Disease Control and Prevention,; the National Safety Council,; and the National Transportation Safety Board,

(2) Dominick and Vincent DiMaio, Forensic Pathology (Boca Raton, FL: CRC Press, 1983).

(3) Ibid.

(4) Ibid.

(5) Bradley Stafford, "The Sinking and Rising of Drowned Bodies" (unpublished thesis, 1988).

(6) Robert Teather, The Underwater Investigator (Fort Collins, CO: Concept Systems, 1983); and Robert Teather, Encyclopedia of Underwater Investigations (Flagstaff, AZ: Best Publishing, 1994).

(7) Supra note 5.

(8) Supra note 6.

(9) Supra note 6.

(10) Supra note 6.

(11) Charles Swanson, Neil Chamelin, and Leonard Territo, Criminal Investigation (New York, NY: McGraw-Hill, 1996).

(12) Bernard Knight, The Coroner's Autopsy (London, England: Churchill Livingstone, 1983).

(13) Supra note 6.

(14) Supra note 6.

(15) Supra note 6.

(16) Supra note 6.

(17) Supra note 6.

(18) Supra note 11.

(19) Supra note 2.

(20) Supra note 2.

(21) Supra note 6.

An Online Resource

To assist investigators in conducting drowning investigations, the Missouri State Water Patrol offers an easy-to-follow resource. The Supplemental Underwater Recovery Report is available on the agency's Web site at
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Author:Haupt, Gary
Publication:The FBI Law Enforcement Bulletin
Geographic Code:1USA
Date:Feb 1, 2006
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