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

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

Force Force = mass x acceleration Force is a push or pull applied to an object Forensic Science II: Physical Trauma, Chapter 7 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

Blunt-Force Trauma (Obj 7.2) Abrasions Contusions Lacerations Forensic Science II: Physical Trauma, Chapter 7 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

Sharp-Force Trauma (Obj 7.3) Stab Wounds Incised Wounds Chop Wounds Therapeutic Wounds Forensic Science II: Physical Trauma, Chapter 7 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

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 © 2012 Cengage Learning. All Rights Reserved

Therapeutic Wounds Caused by surgery or other medical procedures Avoid confusion between therapeutic and inflicted wounds Forensic Science II: Physical Trauma, Chapter 7 © 2012 Cengage Learning. All Rights Reserved

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

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

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

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