Chapter 7Physical Trauma

For each type of injury listed, propose the type of weapon/instrument that might cause that type of injury.

Abrasion Chop wound Contusion Hesitation marks Laceration Therapeutic wound

Vocabulary

Work with the person sitting next to you to come up with a definition of physical trauma

Provide 5 examples of physical trauma Which of your examples are life threatening?

Physical Trauma

Choose a partner and stand 3 feet apart and face each other

Pretend to hold a knife in your left hand and model a stabbing motion

Observe the angle at which the knife hits the victim

Repeat the procedure with your right hand then switch roles with your partner

How can you tell if the agressor is right-handed or left-handed?

2008 – 11 million crimes of which 1.3 million were violent

Of the 1.3 million violent crimes 16,000 resulted in death and the remainder suffered from physical trauma

Physical trauma – any serious or life-threatening physical injury, wound, or shock

Introduction

1. blunt-force – victim hits or is hit by a hard object

2. sharp-force – victim is poked, cut, or stabbed by something sharp

Types of physical trauma

Evaluates the physical trauma and interprets the injuries

Can provide a profile of the suspect For example: What will the angle of the

impact tell you about the suspect? What about the location of the trauma?

Forensic Nurse

Appearance and extent of injuries depend on the following:

A) amount of force applied to body B) mass and surface area of weapon C) part of the body affected

Evidence of Physical Trauma

A push or a pull applied to an object Calculation Force = mass x acceleration(F=ma) Acceleration is the change in velocity over a period of

time Ex) a car traveling at 45 mph – it’s velocity = 45 mph

or 2o meters per second If the car suddenly stops then the change in velocity =

20 meters per second If it takes 2 seconds to stop then the acceleration is 10

meters/s/s or 10 m/s2(this is negative acceleration)

Force

1. How would the force change if the vehicle in the previous problem had a greater mass? Substitute the mass with a different number to support your answer.

An attacker swings a board with a mass of 2 kg toward a victim. The acceleration is 10m/s2 when the board hits the victim. How much force did the board exert on the victim?

Practice problems

If the same amount of force is exerted over a larger surface area, the injury will be less severe because pressure = amount of force per unit area or P = F/A

Ex) if you push against a wall with your palm that has a surface area of 129 cm2 using 44.5 N of force, what is the pressure?

Ex) now use the same force but with a closed fist that has a surface area of 38.7 cm2

How does the pressure change? Why do women wearing high-heeled shoes walk on the tips of

their toes when walking on soft surfaces such as a muddy lawn? T or F A weapon with a larger surface area will inflict a less

severe injury if force is kept constant.

Surface Area and Pressure

Develop 3 force word problems 1 should have you solving for force 1 should have you solving for mass 1 should have you solving for acceleration Problem should be centered on a victim who

suffered from a specific kind of trauma

Creating your own word problems

1. Blunt force trauma – hit by something hard, falls or is pushed into a hard object

2. Sharp force trauma – injury caused by sharp or pointed weapon

Types of Trauma

1. Abrasions – if part of the body rubs against a rough surface - portion of the epidermis may be removed

Blunt force trauma

1. receptors to detect pain, touch, pressure, and heat

2. temperature regulation 3. excretion 4. prevent water loss 5. protect body against pathogens

Function of skin

When force is applied parallel to the skin – ex) if victim is dragged along a rough surface

Skin is damaged in the direction of the force Wound may contain debris, gravel, or glass May also be produced by a noose or tie that

would leave fibers

A. Brush Abrasions

When force is applied perpendicular to the skin/skin may be crushed

B. Impact abrasions

If the object leaves a pattern on the skin

C. Patterned abrasion

Aka – bruise – broken blood vessels below the surface of the skin or involving internal organs

Contusion vs livor mortis – how to tell the difference Called a hematoma if blood causes swelling – ex) subdural

hematoma Severity determined by force and type of tissue Patterned contusion Use CT scan to visualize contusions to internal organs Children and elderly most vulnerable to bruising Bleeding disorders also increase the likelihood of bruising Shock – extensive blood loss

Blunt Force Trauma - Contusions

Laceration – a tear in the tissue caused by sliding or crushing force

- caused by extreme force from a blunt object - irregular edges, may have pattern - may occur internally or externally Defensive Wounds – abrasions and contusions on hands,

wrists, or arms - may hold trace evidence from

weapon - called offensive wounds if

perpetrator is injured

Blunt Force Trauma – Lacerations and Defensive Wounds

Sharp weapons such as knives 4 categories – stab, incised, chop, or

therapeutic

Sharp Force Trauma

Most are caused by single-edged kitchen, pocket, or folding knives/4-5 inch blade

Hesitation marks Perforating vs penetrating wound Hilt – may leave patterned abrasion

Stab Wounds

Wound is longer than it is deep because force is applied parallel to the skin

Do not offer clues about the weapon Generally not fatal Can be defensive wounds

Incised Wound

Tools such as axes, machetes, and meat cleavers

Surface and internal injuries that sometimes include bone fractures

Examination of bone markings can differentiate a cleaver from a machete

Therapeutic wound – produced as a result of surgery

Chop wound and therapeutic wounds

For each of the types of blunt force and sharp force trauma described in your textbook, create a table that includes the following information:

Name of injury Possible weapon Description of injury Due before you leave today and may be

used on test tomorrow.

Assignment