1. Classification of Trauma

2. Types of Trauma Mechanical Chemical Thermal Electrical
Medical doctors and surgeons may classify wounds differently than medical examiners and forensic pathologists

3. Mechanical Trauma
Occurs when the force exceeds mechanical or tensile strength of that tissue
Resulting from sharp or blunt force
Size, shape, and kind of wound may allow the forensic pathologist to determine if a sharp or blunt object caused it
Judicious interpretations and caution are required because of the flexible nature of many of the body’s tissues and the variability of the violent force
Death from blunt and sharp trauma results from multiple processes

4. Mechanical Trauma: Sharp Force
Refers to injuries caused by sharp implements, such as knives, axes, or ice picks
Takes significantly less force for a sharpened object to cut or pierce tissue than what is required with a blunt object
Produce incised wounds – more depth than length or width

5. Mechanical Trauma: Sharp Force
Sharp objects produce incised wounds - a wound that has more depth than length or width
Sharp trauma most commonly causes death from a fatal loss of blood (exsanguination) when a major artery of the heart is damaged

6. Mechanical Trauma: Blunt Force
Caused by dull or non-sharpened objects, such as baseball bats, bricks, or lamps
Blunt objects produce lacerations, or tears in the tissue, typically the skin
Blunt trauma causes death most often when the brain has been severely damaged

7. Mechanical Trauma: Blunt Force
Contusion – an accumulation of blood in the tissues outside the normal blood vessels and is most often the result of blunt impact
The blood pressures the tissues enough to break small blood vessels in the tissues, and they leak blood into the surrounding area
The pattern of the object may be transferred to the skin and visualized by the blood welling up in the tissues
An extreme contusion, a hematoma, is a blood tumor, or a contusion with more blood

8. Mechanical Trauma: Blunt Force
Gunshot wounds – the projectile from a discharged firearm produces a special kind of blunt force trauma
There are 4 major classes of gunshot wounds
Contact (entrance)
Intermediate (entrance)
Distant (entrance)
Shored exit

9. Mechanical Trauma: Blunt Force
Contact (entrance) – distance is 0
Blackening of the skin; lacerations from escaping muzzle gases; bright red coloration of the blood in wound from carbon monoxide gases reacting to hemoglobin in blood (carboxyhemoglobin)
Intermediate (entrance) – 0.5cm-1m
Unburned gunpowder penetrate skin and burns it, causing small red dots called stippling; the stippling pattern enlarges as the muzzle-to-target distance increases

10. Mechanical Trauma: Blunt Force
Distant (entrance) – >1m
Speed of gunpowder is insufficient to cause stippling at this distance; lack blackening: no carboxyhemoglobin; circular defect with abraded rim; distance intermediate
Shored exit
Skin is supported or shored by some material, such as tight clothing, wall board, or wood, as bullet exits; may look very similar to entrance GSW except pattern of shoring material (such as the weave of cloth) may be transferred to skin as it expands when bullet exits

11. Chemical Trauma
Damage and death that results from the interaction of chemicals with the human body
This is the domain of the forensic toxicologist (discussed later)
If the damage from chemicals is external (acid or alkaline burns) then it is still the responsibility of the pathologist

12. Thermal Trauma Extreme heat or cold also may produce death
Hypothermia – too much exposure to cold
Hyperthermia – exposure to excessive heat
Either condition can interfere with the normal physiological mechanisms that keep body temperature at about 98°F/37°C

13. Thermal Trauma
In both cases, the forensic pathologist may encounter few signs at autopsy that will indicate either of those mechanisms; more commonly, external or environmental factors, as well as what is not found, may lead to this determination

14. Thermal Trauma
Individuals in a vulnerable state of health – the sick, the very elderly, or the very young – most often succumb to hypo- or hyperthermia
Other factors may contribute, such as alcohol, which reduces sensitivity to cold and dilates (opens) the blood vessels, speeding the cooling of the body

15. Thermal Trauma
Hyperthermia deaths are common in elderly people in northern cities and infants left in automobiles during the summer
The inside temperature of a closed car in the sun can exceed 140°F/60°C and can be fatal to an infant in 10 minutes

16. Thermal Trauma
Thermal burns tend to be localized; persons who die in a fire do so generally because of a lack of oxygen (asphyxia) and the inhalation of combustion products, like CO
The level of CO in the tissues can determine whether the person was alive or dead when the fire burned him or her
A body from a burned building with 1 or 2% CO is presumed to have been dead (or at least not breathing) at the time the fire started.
True deaths from thermal injuries do occur due to either massive tissue damage and/or swelling of the airway, causing suffocation

17. Electrical Trauma Electricity can cause death by a number of means
Circuits of alternating current (AC) at low voltages (<1,000V) that cross the heart cause ventricular fibrillation, a random quivering that does not pump the blood through the body properly
A person in ventricular fibrillation for even a few minutes cannot be resuscitated
The heart fibrillates because the current is acting like a (faulty) pacemaker
AC in the US alternates from positive to negative at 3,600 times/minute and at 2,500 times/minute in Europe; the heart can beat only about 300 times/minute maximum

18. Electrical Trauma
At high voltages, the amount of current causes the heart to stop beating (it becomes defibrillatory) pushing the heart into tetany, a sustained contraction that is broken only when the circuit is broken
Although the heart will generally start beating normally again, high voltages produce severe burns and cellular damage within a fraction of a second