forensics hosa 25'

Week 1 · Death Investigation

Background 

• In English-speaking countries, the coroner is the government agent charged with responsibility for death investigations

• In 1877, the Massachusetts legislature passed a statute that replaced coroners with medical examiners and required medical examiners to be licensed to practice medicine

Forensic pathologists - physicians specializing in pathology (the diagnosis of disease) + sub on law and medicine of cause of death (studies disease, its causes, and its diagnosis) 

• WHY?

• Determine cause and manner 

• Present physical evidence 

• Support conclusions about cause and manner

• Cause of Death

• disease or injury that initiated the chain of events, (brief or prolonged) that led to death

• The underlying cause (E.g. Multiple gunshot wounds→ those injuries set in motion a lethal chain of events)

• I.e stab or gunshot

• Mechanism of Death

• biochemical or physiological abnormality produced by the cause of death that is incompatible with life (E.g. multiple-organ failure)

• Chemical reaction or lack thereof in the body that results in the victim’s death

• I.e cardiac dysrhythmia, sepsis

Manner of Death (Fashion in which cause of death came to be 4)

1. Natural

• Caused only by disease with no trauma 

• (E.g. diabetes, old age, pre-existing health issues)

2. Accidental

• Due to trauma occurring from accidental acts 

• low probability of producing death 

• (e.g. slip and fall, traffic collisions)

3. Homicidal + suicidal

• Caused by intentional acts

• High probability of injury/death

• Suicide - person who died is the person who  caused the death

• Homicide - someone else committed it

• Difference between the two is the person who acted

Time of death (Estimated with changes of body) by

• Rigor Mortis “Stiffening of muscles that occurs after death”

• Chemical reaction 

• Occurs when glycogen is used up following death 

  • Glycogen - In muscles; provides energy for the contraction of muscles; depleted slowly after death

• Seen about 4 hrs after death

• Disappears after about 24 - 36 hrs after death 

  • Further decomposition of muscles leads to loss of ability to remain fixed in rigor

• Livor Mortis “Discoloration of the body that occurs from the settling of red blood cells after the blood stops circulating”

• Can be seen within minutes. blood cells have increased sedimentation rate due to disease

  • light-skinned - lividity can be seen within 1hr. or so after death

  • Some dark-skinned - lividity may not be visible

• May not be visible if a person died and lost most of their blood

• Finger pressure will not blanch the lividity about 12 hours after death

• Lividity slowly disappears with decomposition after 36 hours

• Algor Mortis “Cooling of body after death”

• Occurs if body temp is higher than atmosphere temp 

• Nearly nude body exposed to 18° to 20°C = l.5°C of temp drop/h for the first 8 hours

• Normal body temp. = 37°C

Tools of Investigation 

• Reviewing Medical History (e.g. death is reported to the coroner or medical examiner…)

• Determine if jurisdiction exists to investigate the death injury 

• Was the death sudden? Unexpected? 

• Usually able to differentiate b/w injuries before and after death 

• Difficult when vigorous CPR has taken place

• Reviewing Witness Statements

• Knowing what witnesses recall of activities prior to death or injury is important

• Forensic pathology deals with recreating the circumstances of death, so knowing what witnesses say happened is extremely valuable in developing questions to be answered

Scene Examination

• Autopsy (dissection of human body to determine the cause of death)

• practiced since early Middle Ages

• more technically correct term for the dissection is necropsy (looking at the dead)

• Prohibitions by religion make performing an autopsy difficult

• Requires permission by living next of kin, unless next of kin is suspect

• Objections by next of kin to autopsy or specific aspects of autopsy are respected as far as possible

Week 2 · Death Investigation (con.)

Tools of Investigation (cont.)

• Autopsy (process) + Dissection of human body

• Documentation & Specimens

• Remove internal organs through incisions (Inframammary incision)

• Starts at shoulder, extends to the middle of body (in lower chest), then to the top of the pubic bone

  • T-shaped incision

  • Most used technique

  • Remove organs in chest and abdomen

• Brain examination (remove head)

  • Make an incision from behind one ear to the other 

  • Peel scalp upward and backward

  • Saw skull in circular/tonsorial cut & remove skull cap

• Documentation & Specimens

• Pathologists must collect samples needed by other forensic professionals 

E.g. toxicologists and DNA analysts

• Some drugs redistribute in the postmortem (after death) period 

• Venous blood is considered more reliable than heart or aorta blood for many drugs

Alcohol is generally measured in the blood v.s. Opiates + diazepines + cocaine Mes. in the urine

Investigating Traumatic Death

• Traumatic Death

• All 4 manners of death are applicable to all these deaths (traumatic deaths are most often investigated)

• Whatever the underlying manner of the traumatic death is, it is frequently the subject of a death investigation

• There are 4 classifications of traumatic deaths

  • Mechanical

  • Thermal

  • Chemical

  • Electrical

• Asphyxias

• Interruption of oxygenation of the brain

• Drowning

• Asphyxiation from immersion in liquid

• Manual strangulation

• Constricting airway by compressing neck

• Chemical causes or electrical causes

• Cyanide poisoning, low voltage electrocution

• Mechanical Trauma

• Caused by force/a physical act (Occurs when applied physical force > tissue’s tensile strength)

• Sharp force injury, blunt force trauma, firearms

Contusion - when blood accumulates in tissue outside the blood vessels

Hematoma - contusions w/ more blood 

• Sharp Force Injury

• Sharp instrument used

  • Easier to create mechanical trauma w/ this than blunt object

  • Produce incised wound (cut)

• Stab wound - produced by sharp object that has more depth than other surface dimensions

• Blunt Force Trauma (Lacerations caused by a blunt object)

• Causes death most commonly when the brain has been damaged; but, blunt force trauma can lacerate the heart or aorta, leading to exsanguination, or can produce other complications

• Most common blunt force injuries are from transportation collisions

• With the exception of gunshot wounds, homicidal blunt trauma in an adult requires a lethal head injury, injuries to other areas of the body rarely produce death

• Firearms

• Most common suicidal & homicidal wounds in the U.S.

  • Availability of firearms 

  • Lethality of firearms

• Cutoff point b/w high & low velocity = 300 m/s

• Electrical Trauma

• The passing of electricity through a person can lead to death 

• If a circuit of alternating current (AC) below 1000 volts crosses the heart, the heart will experience ventricular fibrillation ( a quivering that leads to non-resuscitability within minutes)

• Low voltage can cause electrical burns due to long exposure

• Ventricular fibrillation is less likely with high voltage because the current becomes defibrillatory instead offibrillatory

• High-voltage currents forces the heart into tetany (a sustained contraction that is broken when the citcuit is broken)

• Chemical Trauma (Include deaths due to the use of drugs and poisons)

• Ethanol (ethyl alcohol) = most common drug in forensics. It is mostly a contributory factor in ~ 50% of traumatic deaths

• Drugs generally produce death from the same mechanism

• these drugs include barbiturates, diazepams, and opiates

• they all lead to increasing levels of coma followed by decreased levels of breathing and death

• Cyanide is similar to CO2 in that it interferes with the oxygenation of the brain, acting primarily on the enzymes in the mitochondria of the brain

• Thermal Trauma

• Exposure to excessive heat or cold, thermal trauma, may produce death

• Hypothermia is excessive cold; Hyperthermia is excessive heat

• Both conditions can cause death via a breakdown in the normal mechanisms that maintain body temperature around 37°C

• Homeostasis is constant body temperature