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Forensic Science - 09 Autopsy


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A closer look at how an autopsy can help forensic scientists in their criminal investigation.

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Forensic Science - 09 Autopsy

  1. 1. DRYSDALE CSI Autopsy. Ian Anderson Saint Ignatius College Geelong
  2. 2. WHAT IS AN AUTOPSY?  An autopsy (or post-mortem examination) is a specialized examination of a corpse in order to determine how and why someone died. Source:
  3. 3. WHAT IS AN AUTOPSY?  There are two classifications for autopsies:  Forensic autopsy.   Required when:  Criminal activity is suspected.  Where the body has not been identified.  Where the cause of death is not clear.  Also often required in cases involving accidental death. Clinical autopsy.  Undertaken in an attempt to prevent future deaths. e.g.  To investigate a new disease, or  The effects of a particular treatment.
  4. 4. WHAT IS DEATH?  Death is cessation, or end, of life.   How do you determine this? If you came across someone lying on the ground and they were cold to the touch and comatose are they dead?  In the 17th Century anyone in a coma or with a weak heartbeat were presumed dead and buried. Many were buried with a bell. Why?  Saved by the bell!  Source: top-10-buried-alive-movies-20100929-15x4y.html/
  5. 5. THE MANNER OF DEATH.  There are four ways that a person can die:  Natural death.    Accidental death.   When someone deliberately kills themself. Homicidal death.   Death caused by unplanned events e.g. car accident, falling off a roof, etc. Suicidal death.   Interruption and failure of body functions resulting from age or disease. The most common manner of death. The death of one person caused by another person. Sometimes the coroner will list the manner of death as ‘unknown’ as a definitive determination of the manner of death cannot be made.
  6. 6. CAUSE AND MECHANISM OF DEATH.  Cause of death. Describes the event that lead to a person’s death.  e.g. stroke, heart attack, drowning, burning, strangulation, etc.   Mechanism of death.  Describes the specific change in the body that brought about the cessation of life.  e.g. loss of blood, cardiac arrest, cessation of brain function, etc. Source: s-Bay-man-missing-feared-drowned-20121120
  7. 7. TIME OF DEATH.  Estimation of the time of death can be important in cases of suspicious death.   e.g. a suspect may be proven innocent because they were not in the same place as the victim at the time of death, or a suspect may remain a person of interest because they were in the same area as the victim at the time of death. Early post-mortem changes can be used to determine the time that has elapsed since death occurred (called post-mortem interval).  This because the body changes and eventually decomposes in predictable ways after death.
  8. 8. TIME OF DEATH.  Early post-mortem changes.  Algor mortis (changes in body temperature).   The most accurate measure available for estimating the time of death (particularly in the first 18 hours post-mortem) When alive our body temperature is ~37°C. After death the body cools (or heats) at a predictable rate until it reaches the surrounding environmental temperature.  Approximately one hour after death the body cools at a rate of 0.78°C per hour. After 12 hours the body loses about 0.39°C per hour until it reaches the same temperature as its surroundings.  Other factors (e.g. size of the victim, what they are wearing, atmospheric conditions, etc.) may alter the cooling rate.  Changes in decomposition after approximately 42 hours post-mortem will result in the core body temperature rising slightly.
  9. 9. TIME OF DEATH.  Early post-mortem changes.  Livor mortis (Hypostasis). Post-mortem, blood settles in the lower blood vessels of the body due to gravity, resulting in discolouration of tissues (lividity).  The extent of livor mortis in various tissues can help to determine the post-mortem interval, the position of the body at death and whether it has been moved.  Develops shortly after death; becomes apparent within 2 hours; is fully developed after 3-4 hours; and usually lasts until decomposition.  A less reliable indicator of time of death than rigor mortis.  Source: Bertino & Bertino, 2012
  10. 10. TIME OF DEATH.  Early post-mortem changes.  Rigor mortis (Hypostasis). The stiffening of the body that occurs in the early stages after death.  Immediately after death the body is flaccid, however within two hours the stiffness starts in the head and gradually works its way down to the legs. The stiffness gradually disappears after 36 hours.  Occurs because the skeletal muscles temporarily contract and cannot relax.  Not as accurate as measuring core body temperature, but more accurate than using livor mortis.  Source:
  11. 11. TIME OF DEATH.  Early post-mortem changes.  Stomach & intestinal contents.   The amount of food found in the stomach and/or in the intestines can be used to determine time of death.  If undigested food found in the stomach, then death occurred 0-2 hours after the last meal.  If the stomach is empty, but food is found in the small intestine, then death occurred 4-6 hours after a meal.  If the small intestine is empty, but wastes are found in the large intestine, then death probably occurred 12 or more hours after a meal. Changes to the eye.  Following death the surface of the eye dries out and a thin film forms 2-3 hour later if eyes were open, and within 24 hours if the eyes were closed at death.
  12. 12. TIME OF DEATH.  Insect evidence.  Insects can provide detailed evidence about the time of death due to the sequential colonisation of dead bodies by insects. Source: We will look at forensic entomology in detail later.
  13. 13. STAGES OF DECOMPOSITION.  A corpse will decompose in a predictable way over time.  Within 2 days. Green & purplish staining occurs from blood decomposition.  The skin takes on a marbled appearance.  The face becomes discoloured.  Source:
  14. 14. STAGES OF DECOMPOSITION.  A corpse will decompose in a predictable way over time.  After 4 days. The skin blisters.  The abdomen swells due to the CO2 released by bacteria living in the intestines.  Source:
  15. 15. STAGES OF DECOMPOSITION.  A corpse will decompose in a predictable way over time.  Between 6-10 days. The corpse bloats with CO2 as bacteria continues to feed on tissues. Fluids leak from the body cavities as cell membranes rupture.  Eyeballs and other tissue liquefy.  The skin sloughs off.   Between 20-30 days. The gas causes the abdominal cavities & chest to burst and collapse.  Tissues continue to liquefy and gradually dissolve.  Source:
  16. 16. STAGES OF DECOMPOSITION.  A corpse will decompose in a predictable way over time.  After 30 days. The corpse begins to dry out.  When most of the flesh is gone, further decay is very slow from lack of moisture.  Source:
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