Chapter 7 Physical Trauma © 2012 Cengage Learning. All Rights Reserved

Chapter 7

Physical Trauma

© 2012 Cengage Learning. All Rights Reserved

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.

Forensic Science II: Physical Trauma, Chapter 7© 2012 Cengage Learning. All Rights Reserved 2

3

Forensic Science II: Physical Trauma, Chapter 7


3

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 injury, wound, or shock


Evidence of Physical Trauma (Obj 7.1)

• 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.


Force

Force = mass x accelerationForce is a push or pull applied to an object


Surface Area and Pressure

Pressure = force / surface areaPressure 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


Types of Trauma

• Injuries to the body are usually classified as either blunt-force or sharp-force trauma.

• This classification is based on the type of wound produced and the weapon used.

Forensic Science II: Physical Trauma, Chapter 7


9

Blunt-Force Trauma (Obj 7.2)

Caused when a victim:•hits or is hit by a hard object•falls or is pushed into a hard

Types of Blunt force traumas•Abrasions•Contusions•Lacerations



• Massive abdominal blunt force injury often leads to liver injury, since it is the largest internal organ.

• Note the multiple lacerations over the capsule. • Damage to abdominal organs with lacerations,

crush injuries, and rupture can lead to bleeding into the peritoneal cavity known as hemoperitoneum.

• A peritoneal lavage can detect such bleeding.

• abrasion - an injury in which the superficial, or top, layer of skin has been removed due to motion against a rough surface


Blunt-Force Trauma—Abrasions

• Skin has three layers– Epidermis– Dermis– Hypodermis

• Abrasion affects the epidermis, or outerlayer

• Shallow wounds that heal quickly



• Brush Abrasions– When force is applied

parallel to the skin– Example: dragging the body



• 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- when the bruise looks similar to the object that produced it.

• The pattern can give information as to the object used to commit the crime.


Subdural Hematoma



• Contusions on internal organs are not visible externally• CT Scan-use x-rays to check for contusions in deep tissues and

organs

Factors that make internal contusions difficult to detect are:

• 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, wrists, and arms

• Offensive wounds—injuries to the perpetrator• These wounds help substantiate claims by the

victim and perpetrator


Sharp-Force Trauma (Obj 7.3)

Sharp-force trauma—when the victim is poked, cut, or stabbed by something sharp

•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


Stab Wound: Single Edge Blade

Sharp edge Sharp edge of bladeof blade

Stab Wounds

• hesitation marks - jagged and rough superficial wounds caused by someone attempting to take their own life, caused as the person responds to the pain

• Hesitation marks—by suicide victims


Stab Wounds


• hilt - protective piece where the blade meets the handle of a knife

• Penetrating wound—puncturing the organ• Perforating wound—passes all the way

through the organ•


Incised Wounds

• incised wounds - cuts along the surface of the body.

• Produced by sharp-edged objects such as knife, glass, metal, or paper

• Longer than deep• Force usually applied

parallel to the skin• Do not provide clues to

the type of weapon• Clean edges


Chop Wounds

• chop wound - wounds that result in cuts (incised wounds) on the surface and deep internal injuries and/or fractures to bones

• 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 usedForensic Science II: Physical Trauma, Chapter 7© 2012 Cengage Learning. All Rights Reserved 30

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

31Forensic Science II: Physical Trauma, Chapter 7


Therapeutic Wounds• Caused by surgery or other medical

procedures• Avoid confusion between therapeutic and

inflicted wounds• Inflicted wounds are criminal wounds like

stab wounds


Documents

Chapter 7 Physical Trauma © 2012 Cengage Learning. All Rights Reserved