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 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 Accidental Suicidal Homicidal Undetermined 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 Mechanism of death is the specific change in the body that brought about the cessation of life Forensic Science: Fundamentals & Investigations, Chapter 11

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 Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Livor Mortis Lividity begins about two hours after death Discoloration becomes permanent after eight hours Ambient temperature affects the speed of decomposition Lividity can determine the position of the body during the first eight hours Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Rigor Mortis The Rigidity of Death Without oxygen in the blood— Calcium accumulates in the muscles Muscles stiffen Starts in the head and expands throughout After about 15 hours— Muscle fibers begin to dissolve Softening begins 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 2 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 Weight of the body Type of clothing, or lack of it General health of person at time of death Level of physical activity at time of death Sun exposure Forensic Science: Fundamentals & Investigations, Chapter 11

Time of Death—Algor Mortis The Chill of Death Body heat falls after death About 1.5 degrees per hour immediately after death Slowing to less than 1.0 degree per hour after about 12 hours 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 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 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 As the corpse decomposes, 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—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