1. Cause and Mechanism of Death
Cause of death- a disease or injury that initiated the lethal chain of events , however prolonged or brief, that led to death of the person
Mechanism of death- a biochemical or physiologic abnormality produced by the cause of death that is incompatible with life
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2. Cause of Death Examples Drowning Overdose Car crash
Struck by lightning
Blunt force trauma
Gun shot wound (GSW)
Stabbing
Asphyxiation (strangulation)

3. Manner of Death
defined as the fashion in which the cause of death came to be
Types:
Natural
Accidental
Suicidal
Homicidal
Undetermined
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4. Time of Death Three methods used to estimate time of death
Rigor Mortis
Livor Mortis
Algor Mortis
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5. Time of Death
Rigor Mortis- stiffening of muscles which occurs following death:
Results from a chemical reaction with glycogen
ATP is used up and not reformed
Normally sets in about 4 hours after death
Exceptions include instant rigor mortis and death from electric shock- both create shorter onset of rigor mortis from time of death
Generally disappears hours after death
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7. Time of Death
Livor Mortis- discoloration of body from settling of red blood cells after blood stops circulating (aka lividity)
In light skinned individuals, lividity may be seen within an hour after death
In dark skinned individuals, lividity may not be able to be seen
Substantial blood loss may result in little lividity
Lividity becomes fixed about 12 hours after death, and slowly disappears with decomposition after 36 hours
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9. Time of Death
Algor Mortis- cooling of the body after death, and assumes ambient temperature is lower than body temperature
General rule of thumb- a nearly nude body exposed to degrees Centigrade loses 1.5 degrees first 8 hours
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10. Classification of Traumatic Deaths
Traumatic deaths are classified as
Mechanical- sharp and blunt trauma
Chemical- poisoning
Thermal- exposure to excessive heat or cold
Electrical- electrocution
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11. Mechanical Trauma
Mechanical trauma occurs when applied physical force exceeds the tensile strength of the tissue to which the force is applied
Sharp objects produce incised and stab wounds
Example- a stab wound by an object, such as a knife, which has more depth than its other dimensions
Blunt objects produce lacerations
Example- a wound caused by an item such as a brick or stone, which creates significant damage
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13. Mechanical Trauma
Exsanguination- death after a significant loss of blood - a major artery or the heart is damaged and blood loss occurs, and can occur in either sharp or blunt force trauma
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14. Firearm Injuries Firearm projectiles cause blunt trauma
Firearm projectiles are classified by their propellants:
Gunpowder
Smokeless gunpowder- nitrocellulose
Most common suicidal and homicidal wounds are results of firearm blunt trauma
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15. Firearm Injuries Firearm injuries are distinct due to type of weapon
Rifled weapons- rifles, handguns
Smooth bored weapons – shotguns and antique weapons
Injuries produced are result of velocity of projectile
The extent of injury increases as the square of the velocity increases times the mass of the projectile
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17. Firearm Injuries Gunshot wounds can be classified in two manners
Penetrating- creates an entrance wound but not exit wound- projectile must be recovered from body to confirm this
Perforating – creates both an entrance and exit wound- no projectile recovered from body
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18. Firearm Injuries
Distance each component of reaction travels is the basis for determining the distance of the barrel from the victim of the shooting
Gas is projected from barrel only a few inches and creates a near-contact wounds– which creates blackening of skin if victim is close to discharge of weapon
Skin will also show lacerations from force of gas
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20. Firearm Injuries
Carbon monoxide from discharge mixes with hemoglobin and myoglobin in wound to produce carboxyhemoglobin and carboxymyoglobin, which are both bright red in color, compared to normal dull red color of hemoglobin and myoglobin
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21. Firearm Injuries
As the distance of the barrel away from the skin increases, gas diminishes and only unburned powder and bullet can penetrate skin
Stippling- created by unburned powder on skin around defect produced by bullet
Handguns create stippling when held .5 centimeters to 1 meter away from skin
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23. Firearm Injuries Distant gunshot wounds Lack smoke and powder effects
Range is normally indeterminate
Comprised of a circular skin defect and rim of abraded skin around edges
Diameter of skin defect is some indication of diameter of bullet, but not always reliable due to differences in diameters of common bullets
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24. Firearm Injuries
Directionality- direction from which bullet enters and traverses the body.
Emergency room physicians without forensic training who assess directionality of entrance wounds to the body have error rate of almost 100% in assessing direction of wound when an exit wound is present
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25. Firearm Injuries Estimating velocity of exiting bullet
Assess exit wound
Small, slit shaped wounds with few side lacerations are generally from bullets traveling at slow speeds
Exit wounds with many side lacerations generally have traveled at high speeds- military or hunting long arm rifles
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29. Firearm Injuries
Exit wounds are supported or shored if victims wears tight clothing such as a heavy leather coat, or is against a material such as dry wall which will support the skin and allow penetration of the bullet
Shored exit wounds appear to be remarkably like entrance wounds- one must closely note the rim of abrasion of the wound, as it is larger
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31. Firearm Injuries
Entrance wounds are generally round due to being fired from a rifled barrel
Rotation of bullet during flight causes wound to be round or elliptical
Yawing- when a bullet enters a body sideways
Yawing does not normally occur, but can when bullet passes through a medium thicker than air
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32. Firearm Injuries Normally, bullets that exit body waste kinetic energy
However, with handguns, alterations made to a bullet affect the probability of exiting. Designed to enlarge during passage through tissue, they are called
Hollow points
Jacketed hollow points
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34. Blunt Force Trauma
Blunt force trauma can result from motor vehicle accidents
Generally, with exception of gunshot wounds, homicidal blunt force trauma in an adult requires lethal head injury – injuries to other areas rarely produce death
In children, head injuries are most common, however, but chest and abdominal trauma with lacerations to spleen, liver and heart are seen
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35. Blunt Force Trauma
Most common mechanism of death from blunt force trauma is drowning in blood that has aspirated into lungs
Contusion- accumulation of blood in tissue outside the blood vessels- most commonly caused by blunt force trauma
Pattern of blunt object may be transferred to person who is struck
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37. Chemical Trauma
Ethyl alcohol, (ethanol) active ingredient in beer, wine and liquor is a contributory factor in 50% of traumatic deaths
Alcohol is a depressant: it slows reactions and communications from the brain and spinal cord neurons
Person under influence of alcohol breathes slower and slower until lack of oxygen causes death
Around a .30 gram percent of blood alcohol, person goes into coma
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38. Chemical Trauma
Barbituates, diazepams, and opiates produce deaths in same manner as death from alcohol
Cocaine is a stimulant and high doses can cause seizures, extremely high body temperatures and uncontrolled quivering of heart
Marijuana is exception- never known to have produced an overdose death
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39. Stomach full of bags of cocaine

40. Chemical Trauma
Carbon Monoxide (CO) is an odorless, colorless, explosive gas
Deaths due to CO may be accidental, suicidal or homicidal
CO kills by asphyxiation: binds to hemoglobin 300 times more than oxygen and cuts off oxygen to brain
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42. Chemical Trauma
Cyanide is generally available as sodium or potassium salt
Has a distinct odor like almonds
Up to 50% of the population can’t smell cyanide
Forensic Pathologists should be able to smell cyanide, especially in cases of suspected of suicide by cyanide.
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43. Thermal Trauma Exposure to excessive heat or cold may produce death
Exposure to either cause breakdown of body mechanisms that maintain body temperature around 37 degrees Celsius
Hypothermia death common in individuals who are intoxicated by alcohol- alcohol increases loss of body heat and reduces appreciation of the cold
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45. Thermal Trauma
Hyperthermia – heat related illness which can cause death
The ability to maintain homeostasis declines as people age
Thermal burns are wounds caused by hyperthermia- temperatures above 65 degrees C (140 F) will produce burns upon direct contact
People who die at fires most commonly die from inhalation of Carbon monoxide
People who die with only a 1-2% CO level in a burned structure is presumptive evidence they were dead or not breathing when fire started
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46. Electrical Trauma
Passage of electricity through a person may cause death by a number of different mechanisms
Low voltage AC current ( under 1000 volts) crosses the heart and ventricular fibrillation is experienced (nonpropulsive quivering of heart) that leads to nonresucitability within minutes
Heart normally produces 300 quivers per minute
AC produces 3600 quivers per minute
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47. Struck by lightning

48. Electrical Trauma In high voltage exposures:
Poration occurs: result of flow of current through tissues which creates holes in membrane of cells. This creates a devastating loss of limbs in person exposed to high voltage
Electrical current burns person in a fraction of a second
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50. Asphyxias Asphyxia- interruption of oxygenation to brain
Drowning- death from asphyxiation due to immersion in water or other liquid
Water enters stomach, then coughing and reflex inhalation cause water to enter smaller air passages of lungs
Loss of consciousness occurs within 1-2 minutes, unless additional air can be obtained

51. Asphyxias
Diatoms assist in providing clues to determine time and place of drowning
Diatoms are small unicellular one celled organisms found in salt or fresh water
Contain silica, and resist degradation
During late stages of drowning, diatoms in aspirated water are circulated by heart to organs, including bone marrow
Not normally found in bone marrow, diatoms can assist especially if body is severely decomposed or skeletonized
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53. Asphyxias Asphyxia may be caused by: Manual strangulation using hands
Strangulation by ligature
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54. Asphyxias Results of manual strangulation using hands
Typically, manual strangulation fractures the cornu of the thyroid cartilage
Even more common in manual strangulation is hemorrhage of muscles in neck
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56. Asphyxias
In manual strangulation, fracture of hyoid bone in neck is infrequent, and seen in elderly women who have osteoporosis, which makes fracturing the bone easier

57. Asphyxias
Ligature strangulation, whether by hanging or garroting, generally results in findings of a furrow in the neck
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