Investigation of Injury

Anatomical Positions: Planes Sagittal Plane Transverse Plane Coronal Plane

Anatomical Position Right and left is the victim’s right and left Cranial v. caudal Inferior v. superior Ventral v. dorsal Anterior v. posterior Lateral v. medial Proximal v. distal

Physical Trauma The extent and appearance of the injuries depend on: The amount of force applied to the body The weapon’s surface area and mass The part of the body affected

Force Force is a push or a pull applied to an object Describes how hard the weapon hit the victim Force=mass x acceleration or F=ma Acceleration is the change in velocity over a period of time. An object moving quicker will cause a more serious injury

Practice problem If a 1000kg car traveling at 10m/s2 or (45mph with 2 seconds to stop), what would be the force of the impact if it crashed into a wall? F=ma F= (1000kg)(10m/s2) F=10,000kg(m/s2) or 10,000 Newtons What if the speed was increased to 90mph?

Surface area and pressure If the same amount of force is exerted over a larger surface area, the injury will be less severe. Pressure= amount of force per unit area Pressure=force/surface area The force of a palm pushing against a wall is less that the force of a closed fist (decrease surface area=increase pressure/force)

Surface area, Pressure, and force A weapon with a larger surface area will inflict a less severe injury (if same force is applied) What would have more force: A narrow metal rod vs. a flat wooden board? Answer: flat wooden board=more surface area=larger surface area What would be more prone to severe trauma: The skull vs. the back? Answer: the skull=the back has more contact with the weapon=lower pressure=less severe

Blunt Force Trauma An injury resulting from an impact with a dull, firm object or surface Categories of blunt force trauma: Abrasions Contusions Lacerations

Abrasion A scraping injury to the superficial layers (epidermis) of the skin resulting from friction against a rough surface Usually not deep, heal quickly While alive: reddish-brown Post-mortem: yellow, almost transparent Abrasions can be; Brush-force is parallel to skin Impact-force is perpendicular to skin Patterned-brush abrasion that causes an imprint on skin

Abrasions

Contusion (bruise) Hemorrhage into the dermis, subcutaneous tissues, deep soft tissues, and internal organs resulting from a rupture of blood vessels Hematoma: swelling as a result of blood collecting Patterned contusion: the bruise looks similar to the object that produces it

Contusions

Ecchymosis Discoloration caused by the escape of blood into the tissues May or may not be trauma-related, particularly in the elderly

Laceration A tearing or bursting of the tissue resulting from compression or stretching associated with impact from a blunt object or surface Tissue-bridging may occur where the skin splits but the arteries do not forming a ‘bridge’ across the wound

Tissue Bridging

Avulsion Refers to a tearing away or detachment of a body structure Commonly used to describe skin that has been torn away, exposing underlying tissues.

Sharp Force Trauma An injury produced by a pointed or sharp-edged object, and characterized by a relatively well-defined separation of tissues Types: Stab/puncture wound Incised/cut wound Chop wound

Stab/Puncture Wounds Direction of force relatively perpendicular to skin surface

Stab/Puncture Wounds 1.5" Depth of wound generally greater than length on skin surface Depth of wound can be greater than the length of blade that caused it. 4" 3.5"

Stab wound Slit-Like Wound Gaping Wound

Incised/Cut wounds Sharp instrument is drawn across the skin surface Depth of wound is less than length on skin surface 4" 1/2"

Cut/incised wound

Combination of blunt and sharp force injury Chop wounds Combination of blunt and sharp force injury Can result in abrasions, lacerations, cuts, and/or fractures Axes, hatchets, propellers, lawn mower blades

Chop Wounds Abraded Margins

Gun Shot Injuries Contact wound Near contact wound Gun is in contact with victim Near contact wound Gun is very near victim

Gunshot Injuries Intermediate-range wound Distant wound Gun is 3” to 3-4 feet away Powder tattooing (stippling) Distant wound Gun is >3-4 feet away A few inches – 3 to 4 feet > 3 to 4 feet

Powder Tattooing (Stippling)

Gun Shot Injuries Entrance Exit Smaller wound Larger wound Entrance vs Exit Entrance Exit Smaller wound Larger wound Circular, punched-out appearance Jagged edges Abrasion ring No abrasion ring

Entrance Abrasion Ring Exit

Gunshot injuries Penetration: entrance, but no exit Perforation: entrance and exit

Patterned Injuries An injury (generally an abrasion or contusion) that reproduces some of the features of the impacting object Potential misinterpretations Mongolian spots-found on babies, not the result of abuse Periorbital ecchymosis-naturally occurring around eyes Senile pupura

Patterned injuries Senile Purpura Congenital dermal melanocytosis Periorbital Ecchymosis

Many slides and images taken from “Medicolegal Terminology Associated with Wounds Sustained by Victims of Violent Crimes” by Jeff Saviano Jeff Saviano, CFC, CMI Criminalist/Owner JDS Criminalistics, LLC