Evidence: Death and Decomposition (Lesson 2.02)

Overview of Death Investigation

  • A dead body found along a highway prompts several key questions:

    • When did the victim die?

    • How did the victim die?

    • Was the death an accident or a result of foul play?

  • Medicolegal examiners play a crucial role in answering these questions: coroners, medical examiners, and forensic pathologists.

Goals for the Lesson

  • Role of Forensic Examiners

    • Describe the steps forensic examiners take at a possible homicide scene.

  • Definition and Understanding of Death

    • Define death and explore historical and modern methods of determination.

  • Technological Advances and Careers in Forensics

    • Research and evaluate related technologies and career paths.

  • Changes After Death

    • Analyze and describe the sequence of events occurring postmortem.

  • Signs of Postmortem Changes

    • Identify rigor mortis, livor mortis, and algor mortis and their implications.

  • Time of Death Determination

    • Identify data types useful for establishing time of death.

  • Postmortem Interval (PMI)

    • Explain changes after death used to calculate PMI using mathematical and computational methods.

  • Role of Insects

    • Interpret entomological data to evaluate decomposition and PMI determination.

Understanding Death

  • Definition

    • Death has evolved from being viewed as an event to a process.

    • Historical Perspective:

    • Before the 19th century, death was declared if a person had stopped breathing or showed weak heartbeat.

    • This led to fears of being buried alive; some coffins had bells for signaling.

    • Modern Definition:

    • In the 20th century, the advent of resuscitation techniques complicated the understanding of death.

Determining Death

  • A medical expert must declare death:

    • Circumstances dictate who makes this declaration:

    • In hospitals, the attending physician declares death.

    • In public or accidental deaths, the coroner or medical examiner typically makes this determination.

  • Documentation required upon death declaration:

    • Time, date, place, and the name of the declarant, essential for death certificates and jurisdictional purposes.

Investigation of Death

  • Medico-Legal Examiners

    • Include professionals like coroners, medical examiners (ME), and forensic examiners.

    • Forensic examiners are typically not physicians but have medical training.

  • Process of Handling a Death Scene:

    • Police and paramedics initially respond to the scene.

    • The forensic examiner is dispatched to assess the body:

    • Checks for pulse, breathing, pupils, and responsiveness.

    • Declares death if none are detected; this timing is documented.

    • The examiner then surveys the scene and collaborates with law enforcement.

Responsibilities at the Crime Scene

  • The forensic examiner:

    • Takes charge of the body while other evidence is gathered at the scene.

    • Tasks include:

    • Identifying the victim.

    • Photographing the corpse.

    • Making detailed notes on body condition and environment.

    • Collecting evidence from the body.

    • Body temperature may be evaluated to estimate the time of death.

  • Following the investigation:

    • The body is bagged and transported to a morgue for autopsy or family release.

Postmortem Changes

  • Time of Death Estimation:

    • Often unknown unless witnessed; approximation relies on body condition and evidence.

    • Decomposition stages provide clues for time of death.

Stages of Decomposition

  • First 48 Hours:

    • The body initially resembles its living appearance but undergoes several vital changes:

    • Livor Mortis:

      • Skin turns purple at lower body points due to blood pooling (lividity).

      • Observable changes are significant in estimating death timing and body position.

      • Color normalization occurs within 2-8 hours post-death, becoming permanent after about 8 hours.

    • Rigor Mortis:

      • Muscle stiffness begins around 2 hours post-death, peaks at 12 hours, and dissipates after 36-48 hours.

      • ATP depletion leads to muscle contractile changes.

      • Stiffening begins in smaller muscles (face, jaw) before proceeding downward.

    • Algor Mortis:

      • Body cooling post-death indicates temperature drop averages 1.4°F (0.78°C) per hour initially, changing to 0.7°F (0.39°C) after 12 hours.

      • Influenced by external temperatures and other factors.

      • Measurements are used to establish the time of death.

  • Examination of the Eyes:

    • Post-death eyes dry and discolor, becoming cloudy within 2-3 hours (open eyes) to 24 hours (closed eyes).

    • Potassium accumulation in the vitreous humor suggests potential time of death determinations.

  • Stomach Contents:

    • Food digestion times provide additional clues related to time of the last meal:

    • 6 hours for stomach, 12 hours for small intestine, 24 hours for full excretion.

Five Stages of Decomposition

  • Stage 1: Initial Decay (0-3 days)

  • Stage 2: Putrefaction (4-10 days)

  • Stage 3: Black Putrefaction (10-20 days)

  • Stage 4: Butyric Fermentation (20-50 days)

  • Stage 5: Dry Decay (> 50 days)

Role of Coroners and Medical Examiners

  • Upon determining death, a coroner or ME investigates under suspicious circumstances to establish manner, cause, and mechanism of death.

  • Each stage of decomposition informs investigators on the probable time of death, enhancing the investigative process.