Chapter 11 Death: Meaning, Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to: Discuss the definition of death Distinguish between four manners of death: natural, accidental, suicidal, and homicidal Distinguish between cause, manner, and mechanisms of death Explain the development of rigor, algor, and livor mortis following death All Rights Reserved South-Western / Cengage Learning © 2012, 2009 Forensic Science: Fundamentals & Investigations, Chapter 11

Chapter 11 Death: Meaning, Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to: Estimate the time of death Describe the stages of decomposition of a corpse Use evidence on stomach contents to estimate time of death Use insect evidence to estimate time of death Explain how environmental factors can affect the estimated time of death Forensic Science: Fundamentals & Investigations, Chapter 11

Definition of Death Cessation, or end, of life Irreversible cessation of blood circulation Cessation of all brain activity Experts do not agree on a single definition In cases of suspicious death, a forensic pathologist (MD) conducts an examination on the deceased, called an autopsy. The autopsy is conducted to determine the manner, cause, mechanism, and time of death. Forensic Science: Fundamentals & Investigations, Chapter 11

Introduction Death is a process rather than an instant event. When the heart stops beating, the cells of the body begin to die because they no longer receive a fresh supply of oxygen. As oxygen levels drop, the basic processes of the body fail to occur. Nerves, muscles, organs, and the brain stop working. When a cell dies, it breaks down. Once enough cells begin to break down, life cannot be restarted. Cell breakdown is called autolysis. Forensic Science: Fundamentals & Investigations, Chapter 11

Introduction Autolysis—cell breakdown Forensic Science: Fundamentals & Investigations, Chapter 11

The Manner of Death The manner of death can be: Natural, the most common—interruption & failure of body functions resulting from age or disease Accidental—caused by unplanned events (car accident, falling from a ladder, etc.) Suicidal—when a person purposefully kills oneself (hanging, drug overdose, gunshot, etc.) Homicidal –death of one person caused by another person Undetermined –stated on death certificate if the official cause can’t be determined (this leaves room for further investigation) Sometimes the manner of death is difficult to determine Forensic Science: Fundamentals & Investigations, Chapter 11

Cause and Mechanism of Death Cause of the death is the reason for the death. Examples: disease, physical injury, stroke, heart attack, etc. Cases of Death by Homicide: bludgeoning, shooting, burning, drowning, strangulation, hanging, suffocation, etc. Mechanism of death is the specific change in the body that brought about the cessation of life. Examples: loss of blood (exsanguination), cessation of brain function, cessation of heart function (heart failure), cessation of breathing (respiratory failure), etc. Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Livor Mortis During an autopsy, the forensic examiner wants to determine when the person died. Why??? Time of Death—Livor Mortis The Leaden-Color of Death Lividity—With decomposition, blood seeps down and settles in the lower parts of a body Red blood cells turn bluish-purple; the purplish color is visible on parts of the skin wherever the blood pools. The process takes time. Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Livor Mortis (cont) Lividity (the pooling of blood in the body) begins about two hours after death. Discoloration becomes permanent after eight hours. If death occurred between 2 and 8 hours, lividity will be present, but if the skin is pressed, the color will disappear. After 8 hours, if the skin is pressed, the lividity will remain. Ambient temperature affects the speed of decomposition and lividity to set in. If the corpse is left outside on a hot, summer day, livor mortis takes place at a faster rate. If left in a cool room, livor mortis is slower. Because gravity pulls the blood toward the ground, lividity can also determine the position of the body during the first eight hours. Lividity can also reveal if a body has been moved. (p. 213) Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Rigor Mortis The Rigidity of Death (death stiffness) Without oxygen in the blood— Calcium accumulates in the muscles (due to lack of oxygen) Muscles stiffen Starts within 2 hours after death. Starts in the head and gradually works its way down to the legs. After 12 hours, the body is in its most rigid state. After about 15 hours— Muscle fibers begin to dissolve Softening begins The stiffness gradually disappears after 36 hours.*Depending on body weight and temperature, rigor may remain for 48 hours. Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Rigor Mortis Live muscle fibers slide back and forth After death, muscle fibers become locked in a flexed position Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Rigor Mortis Observation Approx. Time Scale The body is at its most rigid state Just over 12 hours No visible signs of rigor Less than 2 hours or more than 48 hours ago Stiffness generally disappears After 36 hours Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Rigor Mortis Factors affecting rigor mortis: Ambient temperature--the cooler the body, the slower the onset of rigor; the warmer the body, the onset of rigor is faster Weight of the body--A person with less oxygen stored (lower in weight) experiences rigor faster; a person with more oxygen stored (heavier in weight) experiences rigor slower Type of clothing, or lack of it--the presence of clothes accelerates rigor mortis; a naked body cools faster, which slows down the onset of rigor mortis Illness--If a person dies with a fever, the body temp will be higher, and rigor mortis will set in faster Level of physical activity shortly before death—If a person was exercising or struggling before death, then rigor will progress faster Sun exposure--A body exposed to direct sunlight will be warmer, and rigor mortis would occur faster Because so many variables can affect how fast rigor mortis progresses, a precise time of death cannot be determined, it can only be estimated. Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Algor Mortis The Chill of Death—temp loss in a corpse Body heat falls after death About 1.4 degrees per hour immediately after death Slowing to about .7 degree per hour after about 12 hours until the body reaches the same temperature as the surroundings Heat loss is affected by the ambient temperature Corpse temperature is measured by a thermometer inserted into the liver Time of death is expressed as a range of time because it can’t be calculated exactly Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death— Stomach and Intestinal Contents In general, it takes 4-6 hours for the stomach to empty its contents into the small intestine and another 12 hours for the food to leave the small intestine. It takes about 24 hours from when a meal was eaten until all undigested food is released from the large intestines. From this, it can be concluded that: Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death —Stomach and Intestinal Contents State of Contents Timing of Death Undigested food present in the stomach Zero to two hours after the last meal Stomach is empty, but food found in small intestine Death occurred at least four to six hours after a meal Small intestine is empty; waste found in large intestine Death occurred 12 or more hours after a meal Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death —Stomach and Intestinal Contents Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death --Stages of Decomposition A corpse decomposes in predictable ways over time that can help examiners judge when death occurred: 1. Within 2 days after death: Cell autolysis begins following death Green and purplish staining occurs from blood decomposition The skin takes on a marbled appearance The face becomes discolored 2. After 4 days: The skin blisters The abdomen swells with the gas carbon dioxide that is released by bacteria living in the intentines Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death --Stages of Decomposition 3. Within 6-10 days: The corpse bloats with carbon dioxide as bacteria continue to feed on tissues. Eventually, the gas causes the chest and abdominal cavities to burst and collapse Fluids begin to leak from the body openings as cell membranes rupture Eyeballs and other tissues liquefy The skin sloughs off 4. See Figure 11-11 on page 317—Stages of Decomposition Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death —Stages of Decomposition Choose: A. Within 2 days. B. After 4 days. C. Within 6-10 days. Fluids begin to leak from body openings as cell membranes rupture Discoloration of the face The skin sloughs off The skin blisters Green and purplish staining from blood decomposition The corpse bloats Eyeballs and other tissues liquefy The abdomen swells Marbling appearance on the skin Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Insects Forensic entomologist Collects insect evidence from on, above, and below the body Records environmental conditions Within minutes of a death, certain insects arrive to lay their eggs on the warm body—blowflies—they are attracted to 2 gases of decomposition As the corpse progresses through the stages of decomposition, other kinds of insects arrive Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death —Blowfly Life Cycle <8 hours after death—blowfly eggs can be found in the moist, warm areas of a corpse Within 20 hours—1st of their 3 larva stages 4th or 5th day—3rd of their 3 larva stages Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death —Blowfly Life Cycle 8 to 12 days—larvae migrates to a dry place 18 to 24 days— Early pupa; immobile; changes from light brown to dark brown By the 21st-24th day the pupa cases will split open and adult blowflies will emerge. Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Insects The insect life cycle provides scientists with a benchmark to estimate a time of death Insect evidence cannot provide an exact time of death because of fluctuating environmental conditions Insect evidence provides a close estimate Forensic Science: Fundamentals & Investigations, Chapter 11

. . . . . . . . . . . . . . . . . Summary Several definitions of death A body decomposing through three stages— livor, rigor, and algor mortis—provides an estimated time of death Stomach contents and insect evidence also aid in estimating the time of death Environmental factors affect the estimated time of death Forensic Science: Fundamentals & Investigations, Chapter 11