Chapter 7 Physical Trauma

Chapter 7—Physical Trauma

Introduction—Objectives

1. Discuss how investigators study injuries to determine the extent, or degree, of injury.

2. Differentiate between the three types of blunt-force trauma.

3. Discuss the four types of sharp-force trauma.

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)

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

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

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

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

Evidence of Physical Trauma (Obj 7.1)

The amount of force applied

The weapon’s surface area and mass

The body part affected

Force

Force = mass x acceleration

Force is a push or pull applied to an object

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

Blunt-Force Trauma (Obj 7.2)

Abrasions

Contusions

Lacerations

Blunt-Force Trauma—Abrasions

Skin has three layers

• Epidermis

• Dermis

• Hypodermis

Abrasion affects the epidermis, or outer layer

Shallow wounds that heal quickly

Blunt-Force Trauma—Abrasions

Brush Abrasions

• When force is applied parallel to the skin

• Example: dragging the body

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

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

Subdural Hematoma

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

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

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

Sharp-Force Trauma (Obj 7.3)

Stab Wounds

Incised Wounds

Chop Wounds

Therapeutic Wounds

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

Stab Wounds

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

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

Therapeutic Wounds

Caused by surgery or other medical procedures

Avoid confusion between therapeutic and inflicted wounds

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.

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.

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

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

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