1. Chapter 7 Physical Trauma
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2. Introduction—Objectives
Discuss how investigators study injuries to determine the extent, or degree, of injury.
Differentiate between the three types of blunt-force trauma.
Discuss the four types of sharp-force trauma.
Forensic Science II: Physical Trauma, Chapter 7
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3. Introduction—Vocabulary
abrasion - an injury in which the superficial, or top, layer of skin has been removed due to motion against a rough surface
chop wound - wounds that result in cuts (incised wounds) on the surface and deep internal injuries and/or fractures to bones
contusion - a bruise caused by broken blood vessels below the skin
force - a push or pull against an object; force equals mass times acceleration (F = ma)
Forensic Science II: Physical Trauma, Chapter 7
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4. Introduction—Vocabulary
hesitation marks - jagged and rough superficial wounds caused by someone attempting to take their own life, caused as the person responds to the pain
hilt - protective piece where the blade meets the handle of a knife
incised wounds - cuts along the surface of the body produced by a sharp-edged object such as a knife, glass, metal or even paper
Forensic Science II: Physical Trauma, Chapter 7
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5. Introduction—Vocabulary
laceration - a tear in the tissue caused by sliding or crushing force
physical trauma - serious or life threatening physical injury, wound, or shock
pressure - the amount of force per unit area
therapeutic wound - a wound caused by incision in a medical setting
Forensic Science II: Physical Trauma, Chapter 7
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6. The Siren and the Slugger
Rihanna and Chris Brown
A verbal argument erupted into a physical confrontation
Brown caused contusions to form on Rihanna’s forehead, left hand, left triceps
He bit two of her fingers
Brown turned himself in, pled guilty to felony assault 6
Forensic Science II: Physical Trauma, Chapter 7
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7. Introduction
Physical trauma—any serious or life-threatening physical ingury, wound, or shock
Blunt force trauma—when a victim hits or is hit by a hard object
Sharp-force trauma—when the victim is poked, cut, or stabbed by something sharp
Forensic Science II: Physical Trauma, Chapter 7
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8. Evidence of Physical Trauma (Obj 7.1)
The amount of force applied
The weapon’s surface area and mass
The body part affected
Forensic Science II: Physical Trauma, Chapter 7
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9. Force Force = mass x acceleration
Force is a push or pull applied to an object
Forensic Science II: Physical Trauma, Chapter 7
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10. Surface Area and Pressure
Pressure = force / surface area
Pressure is the amount of force per unit area
A weapon with a larger surface area will inflict a less severe injury
High-heeled shoe
Ping Pong paddle
Forensic Science II: Physical Trauma, Chapter 7
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11. Blunt-Force Trauma (Obj 7.2)
Abrasions
Contusions
Lacerations
Forensic Science II: Physical Trauma, Chapter 7
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12. Blunt-Force Trauma—Abrasions
Skin has three layers
Epidermis
Dermis
Hypodermis
Abrasion affects the epidermis, or outer layer
Shallow wounds that heal quickly
Forensic Science II: Physical Trauma, Chapter 7
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13. Blunt-Force Trauma—Abrasions
Brush Abrasions
When force is applied parallel to the skin
Example: dragging the body
Forensic Science II: Physical Trauma, Chapter 7
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14. Blunt-Force Trauma—Abrasions
Impact Abrasions
When force is applied perpendicular to the skin
Crushes the skin
Common over bony parts of the body
Patterned Abrasions
When the impact of an object leaves an imprint on the skin
Patterns can be used to identify the weapon
Forensic Science II: Physical Trauma, Chapter 7
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15. Blunt-Force Trauma—Contusions
Also known as a bruise
A trauma caused by broken blood vessels below the skin’s surface
Hematoma—when contusions swell
Subdural hematoma— swelling below the brain’s outer membrane
Patterned contusions
Forensic Science II: Physical Trauma, Chapter 7
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16. Subdural Hematoma Forensic Science II: Physical Trauma, Chapter 7
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17. Blunt-Force Trauma—Contusions
Contusions on internal organs are not visible externally
Skin pigmentation makes detection more difficult
Obese vs. athletic bodies
Children and seniors
Alcoholics
Forensic Science II: Physical Trauma, Chapter 7
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18. Blunt-Force Trauma—Lacerations
A tear in the tissue caused by an extreme sliding or crushing force
Blunt objects
A fall
Vehicle impacts
Lacerations may be internal or external
Irregular edges
Forensic Science II: Physical Trauma, Chapter 7
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19. Blunt-Force Trauma— Defensive & Offensive Wounds
Defensive wounds—usually occur on the hands, writs, and arms
Offensive wounds—injuries to the perpetrator
These wounds help substantiate claims by the victim and perpetrator
Forensic Science II: Physical Trauma, Chapter 7
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20. Sharp-Force Trauma (Obj 7.3)
Stab Wounds
Incised Wounds
Chop Wounds
Therapeutic Wounds
Forensic Science II: Physical Trauma, Chapter 7
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21. Stab Wounds
Most are caused by single-edged kitchen, pocket, or folding knives
Blade is usually 4-5 inches long
A sharp knife requires very little force
Hesitation marks—by suicide victims
Penetrating wound—puncturing the organ
Perforating wound—passes all the way through the organ
Forensic Science II: Physical Trauma, Chapter 7
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22. Stab Wounds Forensic Science II: Physical Trauma, Chapter 7
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23. Incised Wounds
Produced by sharp-edged objects such as knife, glass, metal
Longer than deep
Force usually applied parallel to the skin
Do not provide clues to the type of weapon
Clean edges
Forensic Science II: Physical Trauma, Chapter 7
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24. Chop Wounds Heavy tools—axes, machete, meat cleavers
Incised wounds on the surface
Deep internal injuries
Bone fractures
Characteristics of the wound help narrow down the possible type of weapon used
Forensic Science II: Physical Trauma, Chapter 7
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25. Chop Wounds Weapon Characteristics Axe
Often crushes the bone and tissue
Machete
Produce more obvious lines that are coarse and less distinct
Meat Cleaver
Clean thin wound; unlikely to break bone; thin, sharp lines on the bone
Forensic Science II: Physical Trauma, Chapter 7
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26. Therapeutic Wounds Caused by surgery or other medical procedures
Avoid confusion between therapeutic and inflicted wounds
Forensic Science II: Physical Trauma, Chapter 7
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27. Chapter Summary The extent of the physical trauma depends on
the amount of force applied to the body,
the part of the body affected,
how much of the body’s surface was affected, and
the type of weapon used
Force is equal to mass times acceleration.
The more massive the weapon, the greater the force exerted on the body.
The more the weapon is accelerating upon impact, the greater the force exerted on the body.
Forensic Science II: Physical Trauma, Chapter 7
© 2012 Cengage Learning. All Rights Reserved

28. Chapter Summary
Pressure is equal to force divided by surface area. Assuming that the force is equal, a weapon with a smaller surface area will exert greater pressure than a weapon with a larger surface area.
Abrasions are blunt-force trauma caused when the top layers of skin are damaged.
Contusions are broken blood vessels caused by blunt force and are commonly called bruises.
Lacerations are tears in tissue caused by sliding or crushing blunt force.
Forensic Science II: Physical Trauma, Chapter 7
© 2012 Cengage Learning. All Rights Reserved

29. Chapter Summary Stab wounds— a sharp-force trauma
deeper than they are wide
force is applied toward the body
Incised wounds, or cuts, are
sharp-force trauma caused when
a sharp object is forced along the body
wounds tend to be wider than they are deep
Forensic Science II: Physical Trauma, Chapter 7
© 2012 Cengage Learning. All Rights Reserved

30. Chapter Summary Chop wounds— sharp-force trauma
caused by sharp, heavy objects
incised wounds on the surface, and
deep internal injuries, often including broken bones.
Therapeutic wounds—result of surgery
Forensic Science II: Physical Trauma, Chapter 7
© 2012 Cengage Learning. All Rights Reserved