biological sciences pathology chapter 7 ©2010 elsevier, inc

Biological SciencesPathologyChapter 7

©2010 Elsevier, Inc.

• Pathologist is a medical doctor who studies and diagnoses disease in humans

• Forensic pathologist also studies trauma that leads to the death of an individual– Autopsy involves standardized dissection of a

corpse to determine cause and manner of death

INTRODUCTION


• Cause of death is divided into the primary and secondary causes of death– Primary or immediate cause of death is a three-link causal chain

that explains the cessation of life starting with the most recent condition

• Most recent condition (is due to, or a consequence of)• Next oldest condition (is due to, or a consequence of)• Oldest (original, initiating) condition

– Secondary cause of death includes conditions that are not related to the primary cause of death but contribute substantially to the individual’s demise

– Medicolegal autopsy is performed pursuant to a medical investigation of death for legal purposes

CAUSE AND MANNER OF DEATH


• Manner of death is the way in which the causes of death came to be– Homicide, suicide, accidental and natural– Purpose of autopsy is to establish cause and

manner of death, identify deceased, establish time of death, or collect evidence surrounding death

CAUSE AND MANNER OF DEATH


• The Coroner System– The position of coroner has evolved to encompass the

investigation of unusual, untimely, or suspicious deaths– First coroner and medical examiners in U.S. were in

Maryland colony– Position of coroner today can be appointed or elected,

typically no formal education or medical training is required– A medical examiner is typically a physician who has gone

through four years of university, four years of medical school, four years of basic pathology training and an additional one to two years of forensic pathology training

• Medical examiner is an appointed position

CORONERS AND MEDICAL EXAMINERS


• Black states do not have coroners

Map of Coroner/ME Systems


THE POSTMORTEMEXAMINATION (AUTOPSY)

• External Examination– The Visual Examination

• Begins with description of deceased’s clothing, photographs of body and detailed examination of the entire body

• Trauma is noted on a form that includes notes, sketches, or recorded measurements


• Defense wounds are caused by a victim trying to defend himself or herself against an attacker

VISUAL EXAMINATION

Stippling of gunpowder around a gunshot wound


– Traumatic deaths may be classified as mechanical, chemical, thermal, or electrical

– Mechanical Trauma• Mechanical trauma occurs when the force applied to a

tissue exceeds the mechanical or tensile strength of that tissue

– Sharp force refers to injuries caused by sharp implements» Sharp objects produce incised wounds, or deep wounds

CLASSIFICATION OF TRAUMA


• Blunt force refers to injuries caused by dull or non-sharpened objects– Blunt objects produce lacerations, or tears in the tissue

• Sharp trauma commonly causes death from a loss of blood or exsanguinations

• Blunt trauma commonly causes death from brain contusion or accumulation of blood in the tissues outside the normal blood vessels– Extreme contusion, or hematoma, is a blood tumor

MECHANICAL TRAUMA


• Asphyxia is trauma in which the body is deprived of oxygen– Caused by suffocation, strangulation, or chemical

asphyxiation

MECHANICAL TRAUMA


• Projectile discharged from a firearm produces a special type of blunt force trauma

GUNSHOT WOUNDS


• Chemical Trauma– Interactions of chemicals with the human body

• Thermal Trauma– Hypothermia is too much exposure to cold– Hyperthermia is too much exposure to excessive heat– Sick, elderly, or very young most often succumb to hypo- or

hyper-thermia– Thermal burns are localized

• Persons who die in a fire do so generally because of asphyxia, or lack of oxygen, and inhalation of combustion products

• True thermal deaths occur due to massive tissue damage and/or swelling of the airway



• Electrical Trauma– Electricity can cause death by a number of means

• Ventricular fibrillation is a random quivering of the heart that does not pump the blood through the body properly

– Heart is pushed into tetany, a sustained contraction that is broken only when the circuit is broken



– Care is taken to preserve any trace evidence that may be later submitted to a forensic science laboratory

– Age, sex, ancestry, height, weight, state of nourishment and any birth-related abnormalities are noted during exam

– Body is examined for death-related phenomena that may provide information to the investigation

Classification of Trauma


• Rigor mortis is the stiffening of the body after death due to the membranes of muscle cells becoming more permeable to calcium ions

– Begins two to six hours after death, remains for two to three days 24 – 48 hours.

– Muscles begin to relax when decomposition begins– Rate depends on activity before death and ambient

temperature

THE POSTMORTEM EXAMINATION


– Livor mortis, or post mortem lividity, is the settling of blood due to gravity after the heart no longer circulates it through the body

• Results in purplish discoloration of the skin

• Sets in an hour after death and peaks in three or four hours

• Can indicate if a body has been moved



– Eye examinations also provide clues to pathologist

• Petechiae are pinpoint hemorrhages found around the eyes, the lining of the mouth and throat, as well as other areas

– Also called Tardieu spots



– Swabs (vaginal, oral and rectal) are taken for submission to forensic or toxicological laboratory

• One set is taken for smears, whereby the collected fluid on each swab is wiped across a separate clean glass microscope slide

– Examined for spermatozoa

• Second and third sets of swabs are for serological examinations

– Known head and pubic hairs are collected during autopsy

OTHER EVIDENCE COLLECTED


– Ligatures, or victim’s bindings, are extensively photographed, sketched and collected

– Full set of fingerprints is taken to be referenced against any databases

– For badly decomposed remains, the jaw may be used for forensic dental examination and identification

OTHER EVIDENCE COLLECTED


– After external examination, internal organs are removed

• Stomach contents are examined thoroughly

– Each organ is sectioned and viewed internally and externally

• Samples for microscopic analysis of the cellular structure, or histology, and for toxicology screening are taken

INTERNAL EXAMINATION AND DISSECTION


– Based on principle of sequential changes that occur following death called the postmortem clock

• Body temperature, livor, rigor, and decomposition– Decrease in body temperature is called algor mortis

• Chemical changes in body fluids or tissues• Physiological changes with progression rates• Survival after injuries

DETERMINING TIME SINCE DEATH (POSTMORTEM INTERVAL)


– The rate at which algor mortis occurs is not precise– Eyes are indicator of postmortem changes– Stomach contents may be used to determine PMI

because the stomach empties at a known rate– Decomposition of the body begins almost immediately

• Autolysis is the disintegration of the body by enzymes released by dying cells

• Putrefaction is the disintegration of the body by the action of bacteria and microorganisms

• Four main steps of decomposition are fresh, bloated, decay, and dry

– Dependant upon environmental factors

DETERMINING TIME SINCE DEATH (POSTMORTEM INTERVAL)


• Histology– Examination for evidence of cellular pathologies

resulting from disease, trauma, or preexisting conditions

• Tissue samples taken with a microtome, a machine that makes very thin, very precise slices

• Toxicology– Toxicology screens are broad-based screen tests that

help to determine the absence or presence of drugs and their metabolites in human fluids and tissues

LABORATORY ANALYSIS


• Autopsy Report– No standard reporting form exists, though all

reports should include:• Police report• Medical investigator report• Witness reports• Medical history of the decedent

LABORATORY ANALYSIS


• Exhumations– Exhumation is the digging up or removing of a

deceased individual from a mausoleum• Embalming may obliterate or obscure details that might

otherwise be easily examined– Embalming is a process of chemically treating the dead human

body to reduce the presence and growth of microorganisms, to retard organic decomposition and to restore an acceptable physical appearance

• Consultations– Forensic anthropologists, entomologists and

odontologists may play a role in a death investigation

LABORATORY ANALYSIS


• Medical examiners study disease and trauma that lead to the death of an individual

• Determine cause and manner of death

CHAPTER SUMMARY


biological sciences pathology chapter 7 ©2010 elsevier, inc

Documents

death cause

primary cause of death

medical investigation

time of death

immediate cause of death

manner of death introduction

medical training

medical examiners