2. Introduction  There are many different indicators to help determine the time of death.  Insect evidence  Body temperature  Rigor mortis  Liver mortis  Appearance of the eyes  Stomach contents

3. Body Temperature  Your body temperature is generated by chemical reactions occurring in your body.  Cellular respiration is the most important reaction. Cellular respiration is the process that releases energy from molecules such as glucose and makes it available for cellular use.  Cellular respiration produces ATP (Adenosine Triphosphate) which your body uses for energy.  Heat is generated in the process.  It occurs in the Mitochondria in each cell.

4. Body Temperature  When a person dies cellular respiration stops. No more energy is produced and, as a result, heat is not produced.  So when some one dies their body immediately begins to cool.  Cellular respiration is a very complicated process and a lot of people have trouble understanding it.  However, when you break it down to the basics it is easy to understand.

5. Cellular Respiration  C6H12O6 + O2  CO2 + H2O + ATP (Energy)  C6H12O6 is glucose (sugar)  O2 is oxygen gas.  CO2 is Carbon dioxide gas.  H2O is water.  ATP is energy.

6. Cellular Respiration

7. Body Temperature  When a person dies their body temperature drops at a rate of 0.75 C per hour on average for the first 12 hours (starts at 37 C).  After 12 hours the cooling rate slow to about 0.4 C because the body is closer to the temperature around it.  Eventually the body will reach the environmental temperature and stop cooling.

8. Body Temperature  There are several factors affecting body temperature:  Air temperature – A body will cool faster on a colder night  Body fat – Body fat is an insulator, so the more body fat a person has the slower their body will cool  Clothing – We wear clothing to insulate our bodies, so the heavier the clothing, the slower the body will cool.  Water – A body laying in water will cool much faster. What makes it difficult to determine the time of death.

9. Rigor Mortis  Rigor Mortis the stiffening of muscles after death.  The absence of cellular respiration is the root cause of rigor mortis.  To understand rigor mortis we need to briefly discuss muscles.

10. Muscles and Movement  Muscles are made of muscle fibers.  These fibers are made of units called sarcomeres.  Sarcomeres contain myosin filaments and actin filaments.

11. Muscle movement  During muscle contraction actin filaments slide closer together. Myosin filaments are stationary. When the muscle relaxes actin filaments slide back. The sliding occurs because of myosin heads.  Relaxing and contracting takes energy. ATP provides this energy.

12. Muscle Movement  As mentioned before ATP from cellular respiration provides the energy for muscles to relax and contract.  ATP contains three phosphates which I will represent with P’s. When a phosphate bond is broken energy (chemical energy) is released allowing the muscle to move. The result is a molecule of ADP. Adding a phosphate back to ADP creates another ATP.  APP-P  APP + Energy

13. Muscle movement

14. Rigor Mortis Continued  When ATP is no longer available the myosin heads can not detach, so the muscles stay in a rigid (contracted) state.  It takes 1-2 hours before muscles begin to stiffen.  It begins in the face, jaws, and neck before moving to the upper arms and torso. Finally, it ends in the legs.  It takes 8-12 hours to complete the process  As the muscles break down the body starts to relax again. By 24 to 48 hours the body is totally relaxed again.

15. Livor Mortis (lividity)  The heart keeps blood pumping through the body.  However, after death the heart stops pumping and blood begins to settle closest to the ground due to gravity.  Within 1-2 hours after death blood settles into the lowest parts of the body.  The red blood cells settle and break down into the tissues of the body.  The result is purplish marks which later turn yellow when hemoglobin (protein that carries oxygen in the blood) breaks down.

16. Livor Mortis  The color is known as lividity.  Within 6-8 hours after death the color become permanent where the blood settles.  If the body is moved after 6-8 hours the marks may not agree with the position of the body.  If the lividity turns white when touched then the marks have not become permanent yet. This means the time of death is between 2 and 10 hours.

17. Eye Appearance  If the eyes of the deceased remain open after death then a thin film will develop and they will dry out.  As blood cells in the body break down, potassium is released. It enters the eyes and gives them a cloudy appearance.  This process takes 2-3 hours after death, but will take about 24 hours if the eyes remained closed at the time of death.

18. Digestion and time of death  http://www.mennellmedia.co.uk/VideoProjec ts/ToiletTales/ToiletTales.html. http://www.mennellmedia.co.uk/VideoProjec ts/ToiletTales/ToiletTales.html  After food is chewed and swallowed down the esophagus, the digestive juices released by the pancreas and stomach break it down into substances that are readily absorbed through the small intestine. Material that is not taken up by the body collects in the large intestine, forming fecal matter that is then excreted through the anus.

19. Digestive System

20. Digestion and time of death  After eating, it takes 4 to 6 hours for the stomach to empty its contents into the small intestine.  It takes around 12 hours for food to leave the small intestines.

21. Digestion rules  Undigested stomach contents – death occurred 0-2 hours after the meal.  Stomach empty – death occurred 4-6 hours after the meal.  Small intestines empty – death occurred 12 hours or more after the meal.