Classification of Trauma

Types of Trauma Mechanical Chemical Thermal Electrical Medical doctors and surgeons may classify

wounds differently than medical examiners and forensic pathologists

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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