Forensic Pathology - Dr

Forensic Pathology

Elizabeth J. Miller, M.D.

Forensic Pathology Subspecialty of pathology concerned with identification of remains and determination of cause and manner of death

Forensic Pathology Deaths referred to the medical examiner Violent deaths (accidents, suicides, homicides) Suspicious deaths Sudden, unexpected deaths Deaths without a physician in attendance Deaths in a penal institution

Cause of Death The process that initiates a chain of events resulting in death Atherosclerosis ⇒ MI/arrhythmia GSW chest ⇒ pneumonia MVA ⇒ repair of aortic laceration ⇒ aneurysm at site 10 years later Blunt force injury of head ⇒ altered mental function ⇒ aspiration ⇒ pneumonia

Manner of Death Natural Accident Suicide Homicide Undetermined

Manner of Death Natural Atherosclerosis Pneumonia Cancer Sequelae of ethanol/drug abuse Perforation of gastric ulcer

Manner of Death Accident MVA Ethanol/Drug overdose Drowning GSW Asphyxia

Manner of Death Suicide GSW Stab/incised wound Drug overdose Drowning MVA Asphyxia

Manner of Death Homicide GSW Stab Drug overdose Drowning MVA Asphyxia

Manner of Death Undetermined Insufficient information about the circumstances surrounding death 

Drug overdose—accidental overmedication or suicide

Cause of death unknown Skeletonized remains  No anatomical/toxicological explanation 

Scene Investigation Investigative/medical/legal conclusions rest on an intelligent and thorough scene investigation Identity Approximate time of death Important evidence/clues to circumstances surrounding death  Secure residence  Signs of struggle  Position of body/clothing  Suicide notes  Trash contents

Identification of Remains Visual by relatives or friends Location of body (e.g. In home) ID cards distinctive feature (tattoo, ring, necklace)

Scientific Identification Ante mortem radiographs/medical records Serology/DNA Dental records Fingerprints

Chain of Evidence Item properly identified Item stored so as to prevent tampering Maintain record of what was done with object, by whom, at each change of hands

Establishing Time of Death Witnesses Physical evidence (mail, newspaper) Post mortem changes Putrefaction Insect activity

Changes Associated With Death

Rigor Mortis Livor Mortis Algor Mortis Decomposition

Rigor Mortis Depletion of ATP Involves all muscles simultaneously and evolves at that same rate in all muscles Most evident in small muscles first Classical presentation in order of appearance 

Jaw ⇒ upper extremities ⇒ lower extremities

Onset and disappearance dependent on many variables

Rigor Mortis No rigor—death < 3 hours Developing rigor—death 3 to 9 hours Full rigor—death > 9 hours Passing rigor—death 24 to 48 hours Duration of rigor shorter in warm environment

Rigor Mortis Any activity or condition prior to death that results in decreased ATP accelerates development of rigor mortis Violent/heavy exercise (cadaveric spasm) Severe convulsions High body temperatures

Rigor Mortis May be delayed in: Very weak or emaciated individuals Infants Cold/freezing temperatures

Livor Mortis Mechanism—settling of blood in dependent areas of body Appears within 30 minutes after death Non-fixed/blanching (< 8 to 12 hours) —blood still within capillaries and will shift with change in position Fixed/non-blanching (> 8 to 12 hours) —blood within tissue and will not shift with change in position

Livor Mortis Discoloration Purple—normal (venous blood) Green—sulfhemoglobin (hydrogen sulfide) Pink, cherry-red  

Carboxyhemoglobin (carbon monoxide) ⇑ oxygen (cyanide, hypothermia, refrigeration)

Livor Mortis Important in determining postmortem movement of body, not time of death May be confused with bruising Bruises do not blanch with pressure

Fixation may be delayed by cool temperatures

Algor Mortis Cooling of body by heat transfer following death Conduction—direct contact Radiation—infrared rays Convection—air currents

Algor Mortis Inner core temperatures preferred —decline is slower/regular Rectal Liver Brain

Skin—cools rapidly from exposure to environment, so not useful

Algor Mortis Under average conditions < 3 hours—2.0° F to 2.5° F / hour 3 to 12 hours—1.5º F to 2.0º F / hour 12 to 18 hours—1.0º F / hour

Algor Mortis Tables useful, but must be used within context of case Data tables assume: Peri-mortem temp 98.6  Constant post-mortem temp  No extremes in environmental temp  Other scene variables 

Decomposition/putrefaction Fresh Bloated Active Dry/skeletal

Decomposition Bloated stage ~ 36 to 48 hrs—marbling (breakdown of blood within veins) and skin slip/blistering ~48 hrs—bloating (gas production) ~48 to 72 hrs—green to black discoloration

Decomposition Active decay 3 days to several weeks 

Variables: temperature, insect activity, bacteria

Dry/skeletal stage 2 weeks in hot humid temps Months in snow Years if body changed by adipocere

Animal Activity Land Sea

Preserving Changes Mummification Drying of body—usually in warm/dry climate Skin preserved, internal organs not always

Adipocere Waxy change of fat—usually in high humidity/water Conversion of unsaturated fatty acids to saturated fatty acids via Clostridia enzymes

Accelerating Changes Injury sites—allow access to insects Anything that promotes warmth Obesity Heavy clothing Sepsis

Natural Death—SIDS Usually occurs within 6 months, no more than 10 months Exact mechanism unknown Not caused by smothering or choking

Not contagious Not hereditary Occurs very quickly and is assumed to happen during sleep—no suffering or distress

Natural Death Presenting As SIDS Pneumonia Pyelonephritis Myocarditis Bacterial meningitis MCAD deficiency

Other Cases Presenting As SIDS Accidental suffocation Child abuse

Asphyxia

Asphyxia Anything that interferes with oxygen uptake or utilization Suffocation Strangulation Chemical asphyxia

Suffocation Failure of oxygen to reach blood Smothering Choking Drowning Suffocating gases (displacement of oxygen) 

Hydrogen sulfide gas

Suffocation Smothering—mechanical obstruction of nose and mouth Plastic bag Hand Overlying (can’t distinguish from SIDS)

Suffocation Choking—requires an underlying explanation Intoxication Neurological disorder Psychiatric patient

Suffocation Choking Aspiration of food Foreign objects

Suffocation Mechanical asphyxia-compression of chest Car/other heavy objects Bodies (riots, stampedes) Positional asphyxia Cribs with mismatched mattresses  Intoxicated adults 

Suffocation Drowning Dry vs. wet drowning Need to determine why person drowned

Strangulation External pressure causing closure of the blood vessels and trachea Pressures 4.4 lbs.—jugular veins 11 lbs.—carotid arteries 33 lbs.—trachea

Strangulation Hanging Ligature Manual

Strangulation Hanging Usually suicide Point of suspension POS superior to laryngeal prominence

Strangulation Ligature Usually homicide Transverse mark Evidence of a struggle Conjunctival petechiae  Contusion of strap muscles  Fracture of hyoid bone or superior horns of thyroid cartilage 

Strangulation— Manual Homicide Neck holds (law enforcement)—usually no external injury unless flashlight or baton used Carotid sleeper hold—obstruction of blood flow 



Rapid onset of unconsciousness—must release immediately upon incapacitation Release—complete recovery in seconds

Choke hold—airway compression  

Serious damage/death within seconds Muscular or subcutaneous hemorrhage

Chemical asphyxia Cyanide—almond odor Cherry red discoloration of tissues

Carbon monoxide 50% carboxyhemoglobin lethal level Cherry red discoloration of tissues Quick (6 to 7 minutes) Children and elderly especially sensitive

Burns and Electrocution

Burns Categories Flame Contact Radiant heat Scalding Chemical Microwave

Burns Rule of nines Head—9% Arms—9% (each) Anterior torso—18% Back—18% Legs—18% each Neck or perineum—1%

Burns Degree of injury 1st degree—confined to epidermis 

Skin red without blistering

2nd degree—destroys epidermis, spares dermis 

blistering

3rd degree—destruction of dermis 

Skin surface brown or black

4th degree—destruction of subcutaneous structures (e.g. muscle)

Burns Clothing is protective Death Immediate—smoke inhalation Delayed—sepsis from burns

Burns Must establish Identification of deceased Whether deceased was alive at the time of fire Cause of death Manner of death Any contributing factors 

EtOH, drugs, natural disease

Burns 75% of fire-related deaths due to inhalation of toxic smoke Carbon monoxide (lethal level 50%) 

Children/small animals reach fatal level quicker due to higher metabolic rate

Hydrogen cyanide (lethal level 5 mg/ml)

Burns Weight and height altered Feet and hands may be lost Pugilistic pose—shrinkage of muscle Body of an adult rarely destroyed by house or car fire House fire temp—1200 to 1600 F Crematorium temp—1800 to 2000 F

Children may be consumed by fire

Burns Artifacts of burns Epidural hematoma Fire fractures of bone

Burns Scalding Immersion Splash Steam

Burns Chemical burns Acids (HCL) Bases (lye, bleach) Petroleum products (blistering)

Electrocution Electrocution Ohm’s law—V=IR (volts = current x resistance) Household current 110 volts (alternating) Resistance of skin Dry—100,000 ohms (1.1 mamp)  Wet—1,000 ohms (110 mamp) 

Electrocution Current

Physiologic effect

1 mamp Slight tingle 16 mamp Release wire due to shock 20 mamp Muscular paralysis 100 mamp Ventricular 2000 mamp (2 amp) fibrillation Ventricular standstill 5 amp Electrical burn 20 amp Blows common h/h fuse

Electrocution Low voltage Burns usually present at entry/exit sites 

Caveat—current entering over broad surface, e.g. bathtub electrocution

Death due to ventricular fibrillation

High voltage Electrical burns—chalky white with cratering Charring Death due to ventricular standstill or paralysis of respiratory center

Electrocution Lightning Direct strike Side flash conduction

Death from high-voltage direct current Usually due to burns and injury to respiratory center of brain

Gunshot Wounds

Gunshot Wounds Mechanics of firing Firing pin ⇒ ignition of primer ⇒ ignition of gunpowder ⇒ creation/expansion of gas ⇒ bullet, unburned powder, soot propelled down barrel of gun

Gunshot Wounds Entrance wounds Contact Close range Intermediate Distant

Gunshot Wounds Contact Muzzle imprint Stellate lacerations (if adjacent to bony structure) Gunpowder and soot enters wound

Gunshot Wounds Close range—within 3 inches Increase in distance = increase in diameter of particle deposition and tattooing around entrance wound and decrease in particle density Entrance wound Particles of gunpowder around wound  Soot on skin  Tattooing of skin 

Gunshot Wounds Intermediate range—3 to 36 inches Further increase in diameter of particle deposition and tattooing around entrance wound and further decrease in particle density No soot

Gunshot Wounds Distant range—greater than 36 inches Absence of gunpowder particles, soot, tattooing Difficult to determine exact distance —appearance of GSW inflicted at 6 feet doesn’t differ from one inflicted at 16 feet.

Gunshot Wounds Entrance wounds Usually smaller than exit wounds unless:  Located adjacent to bony structures (stellate)  Bullet deflected prior to entrance

Inward beveling of skull Rim of abrasion

Gunshot Wounds Exit Wounds Usually larger than entrance wounds due to deflection of bullet by tissues Outward beveling of skull No gunpowder particles, soot, tattooing No rim of abrasion 

Shoring of exit

Gunshot Wounds Shotgun Wounds Contact—circular wound with muzzle imprint Close   

Circular wound < 2 feet Scalloped edges at 3 feet Few stray pellets at 4 to 5 feet

Intermediate—6 to 7 feet  

Rim of pellets Wad abrasion

Distant—> 10 feet 

complete spread of pellets

Blunt Force Injuries

Blunt Force Injuries Mechanism—tearing, shearing, crushing Categories Contusion Abrasion Laceration fracture

Blunt Force Injuries Contusion—hemorrhage into the soft tissue surrounding the wound No bruise if blow from wide/smooth object or in area protected by heavy clothes/hair Patterned   

Steering wheel imprint on chest Parallel (train-track) lines from rod, stick, whip Horseshoe shaped—whipping with looped cord

Blunt Force Injuries Contusion If death occurs quickly, no bruise evident—must incise area to detect hemorrhage Color change with time—from periphery to center Color change may be used to “age” the injury— depends on size, extent, depth, local circulation    

Immediately—slight swelling Few hours—light blue/red Week—dark purple > week—greenish-yellow

Blunt Force Injuries Contusion Variables which increase bruising 

Children and elderly • Senile ecchymoses on forearms of elderly

Obese women  Alcoholics with cirrhosis  Aspirin use 

Blunt Force Injuries Contusions Maybe be produced postmortem if severe blow delivered within a few hours of death  

Rare Most common in skin/soft tissue overlying bone

Iatrogenic  

Surgical removal of corneas or globes Removal of vitreous

Blunt Force Injuries Decomposed bodies Hemolysis of erythrocytes may mimic contusions Hemolysis of erythrocytes in genuine contusions also occurs—may be impossible to differentiate between decomp and contusion

Blunt Force Injuries Abrasion—scraping/removal of superficial layers of skin Graze—bullet Scratch—fingernail, sharp edge Brush burn—frictional force (dragging on ground) Binding—handcuffs/rope

Blunt Force Injuries Abrasion Patterned Weave of clothing Threaded pipe Wood grain of baseball bat gravel

Blunt Force Injuries Laceration—blow from blunt objects or falls Bridging of connective tissue within depths of wound Age determination difficult Appearance may not reflect object causing injury In general  

Long, thin objects cause linear injury Flat objects cause irregular, ragged, Y-shaped injury

Blunt Force Injuries Laceration Explore depths of wound for foreign material Determination of direction of wounding abrasion/beveling—side from which blow delivered  Undermining of tissue—side away from which blow delivered 

Blunt Force Injuries Fracture—direct or indirect force on bone Direct   

Focal—small force applied to small area Crush—large force applied to large area Penetrating—large force applied to small area

Indirect—force acting at distance   

Traction—violent contraction of quadriceps m. Angulation—bending resulting in transverse fracture Rotational—twisting resulting in spiral fracture

Blunt Force Injuries Skull fracture, base—usually run in direction of impact Ring fracture—separation of rim of foramen magnum from remainder of base 

Fall from height onto feet or buttocks

Transverse—side-to-side)  

Impact either side of head Side to side compression

Longitudinal—front to back  

Impact on forehead, face, back of head Front to back compression

Blunt Force Injuries Skull fracture, base Bleeding from ears, nose or mouth Hemorrhage into soft tissue of eyelids —raccoon eyes Hemorrhage into soft tissue behind ears—Battle’s sign

Blunt Force Injuries Brain contusion Coup—occur at site of injury 

Blow to the head

Contrecoup—occur directly opposite to the point of impact Classically associated with falls  Frontal and temporal lobes  Virtually never occur in occipital lobe 

Blunt Force Injuries Intracranial hematoma Subarachnoid Epidural Subdural

Blunt Force Injuries Subarachnoid hemorrhage Most common sequela of head trauma Focal or diffuse Traumatic Laceration of veins—most common  Laceration of internal carotid, vertebral, basilar aa. 

Blunt Force Injuries Epidural hematoma—trauma to skull with rupture of artery at point of impact Primarily impact injuries—falls, MVA’s Blood intervenes between dura and inner table skull A fracture is usually present— squamous-temporal bone

Blunt Force Injuries Epidural hematoma Usually confined to side of impact Presentation of symptoms Usually 4-8 hours following injury  Sometimes as soon as 30 minutes or as late as 36 to 48 hours 

Lucid interval prior to development of symptoms

Blunt Force Injuries Epidural hematoma Death due to displacement of brain (mass effect) with brain stem compression

Blunt Force Injuries Subdural hematoma— acceleration/deceleration injury Stretching/tearing of bridging veins Most common lethal injury from head trauma Usually not associated with fractures May occur in absence of obvious sign of trauma

Blunt Force Injuries Subdural hematoma Acute—symptomatic within 72 hrs Subacute—symptomatic between 3 days and 2-3 weeks Chronic—symptomatic after 3 weeks

Blunt Force Injuries Onset of symptoms usually acute (30 minutes) Life threatening at 50 ml Displacement of brain (mass effect) with brain stem compression

Blunt Force Injuries Motor vehicle accidents Patterned abrasions—steering wheel Dicing Seat belt Aortic transection distal to subclavian artery Fat embolism

Sharp Force Injuries

Sharp Force Injuries Stab wound Incised wound Chop wound Therapeutic/diagnostic wound

Sharp Force Injuries Stab wound Usually homicide Length/depth of wound track > width Edges usually without abrasion/contusion

Sharp Force Injuries Stab wound

Size and shape depends on many variables Type of weapon—knife, ice pick, screwdriver  Configuration of weapon  Direction  Movement of blade in wound  Langer’s lines—elastic fibers in skin Appearance of wound margins depend on sharpness of knife 

Sharp Force Injuries Stab wound Determination of angle 

Oblique angle—beveled margin on one side/undermining of skin opposite side

Determination of edge Single edge—squared off edge/sharp edge Double edge—both edges sharp

Sharp Force Injuries Stab wounds Mechanism of death Exsanguination  Tamponade  Complications (infection) 

Sharp Force Injuries Incised wound Longer than deep No bridging (differentiate from laceration) Usually suicidal 

Hesitation marks/scars

Usually not fatal

Sharp Force Injuries Homicidal incised—neck Inflicted from behind Begins high on neck opposite side of cutting hand ⇒ downward ⇒ straight across midline ⇒ upward, ending on opposite side of neck lower than initial point  wound first shallow, then deeper, then shallow 

Sharp Force Injuries Suicidal incised—neck Inflicted from front Short and angled  Right handed—wounds on left side of neck  Slashes downward and medial at oblique angle 

Sharp Force Injuries Chop wound Incised wound with underlying injury to bone Incised and lacerated characteristics 

Cutting and crushing

Sharp Force Injuries Chop wound Axe Machete Cleaver Hoe

Sharp Force Injuries Therapeutic/diagnostic wounds surgical stab wounds Chest tube  Abdominal drain  Thoracotomy/lapartomy incisions  Cutdowns of wrist/antecubital fossae,  Tracheostomy incision 