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 PathologyDeaths referred to the medical examiner

Violent deaths (accidents, suicides, homicides)Suspicious deathsSudden, unexpected deathsDeaths without a physician in attendanceDeaths in a penal institution

Cause of DeathThe process that initiates a chain of events resulting in death

Atherosclerosis MI/arrhythmiaGSW chest pneumoniaMVA repair of aortic laceration aneurysm at site 10 years laterBlunt force injury of head altered mental function aspiration pneumonia

Manner of Death

NaturalAccidentSuicideHomicideUndetermined

Manner of DeathNatural

AtherosclerosisPneumoniaCancerSequelae of ethanol/drug abuse

Perforation of gastric ulcer

Manner of Death

AccidentMVAEthanol/Drug overdoseDrowningGSWAsphyxia

Manner of DeathSuicide

GSWStab/incised woundDrug overdoseDrowningMVAAsphyxia

Manner of DeathHomicide

GSWStabDrug overdoseDrowningMVAAsphyxia

Manner of DeathUndetermined

Insufficient information about the circumstances surrounding death

Drug overdose—accidental overmedication or suicide

Cause of death unknown Skeletonized remains No anatomical/toxicological explanation

Scene InvestigationInvestigative/medical/legal conclusions rest on an intelligent and thorough scene investigation

IdentityApproximate time of deathImportant 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 friendsLocation of body (e.g. In home)ID cards distinctive feature (tattoo, ring, necklace)

Scientific Identification

Ante mortem radiographs/medical recordsSerology/DNADental recordsFingerprints

Chain of Evidence

Item properly identifiedItem stored so as to prevent tamperingMaintain record of what was done with object, by whom, at each change of hands

Establishing Time of Death

WitnessesPhysical evidence (mail, newspaper)Post mortem changes

PutrefactionInsect activity

Changes Associated With Death

Rigor MortisLivor MortisAlgor MortisDecomposition

Rigor MortisDepletion of ATPInvolves all muscles simultaneously and evolves at that same rate in all musclesMost 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 hoursDeveloping rigor—death 3 to 9 hoursFull rigor—death > 9 hoursPassing 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 convulsionsHigh body temperatures

Rigor Mortis

May be delayed in:Very weak or emaciated individualsInfantsCold/freezing temperatures

Livor MortisMechanism—settling of blood in dependent areas of body

Appears within 30 minutes after deathNon-fixed/blanching (< 8 to 12 hours)—blood still within capillaries and will shift with change in positionFixed/non-blanching (> 8 to 12 hours)—blood within tissue and will not shift with change in position

Livor Mortis

DiscolorationPurple—normal (venous blood)Green—sulfhemoglobin (hydrogen sulfide)Pink, cherry-red

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

Livor Mortis

Important in determining post-mortem movement of body, not time of deathMay 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 contactRadiation—infrared raysConvection—air currents

Algor MortisInner core temperatures preferred—decline is slower/regular

RectalLiverBrain

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 / hour12 to 18 hours—1.0º F / hour

Algor Mortis

Tables useful, but must be used within context of caseData tables assume:

Peri-mortem temp 98.6Constant post-mortem tempNo extremes in environmental tempOther scene variables

Decomposition/putrefaction

FreshBloatedActiveDry/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 decay3 days to several weeks

Variables: temperature, insect activity, bacteria

Dry/skeletal stage2 weeks in hot humid tempsMonths in snowYears if body changed by adipocere

Animal Activity

LandSea

Preserving ChangesMummification

Drying of body—usually in warm/dry climateSkin preserved, internal organs not always

AdipocereWaxy change of fat—usually in high humidity/waterConversion of unsaturated fatty acids to saturated fatty acids via Clostridia enzymes

Accelerating Changes

Injury sites—allow access to insectsAnything that promotes warmth

ObesityHeavy clothingSepsis

Natural Death—SIDS Usually occurs within 6 months, no more than 10 monthsExact mechanism unknown

Not caused by smothering or choking

Not contagiousNot hereditaryOccurs very quickly and is assumed to happen during sleep—no suffering or distress

Natural Death Presenting As SIDS

PneumoniaPyelonephritisMyocarditisBacterial meningitisMCAD deficiency

Other Cases Presenting As SIDS

Accidental suffocationChild abuse

Asphyxia

Asphyxia

Anything that interferes with oxygen uptake or utilization

SuffocationStrangulationChemical asphyxia

Suffocation

Failure of oxygen to reach bloodSmothering ChokingDrowningSuffocating gases (displacement of oxygen)

Hydrogen sulfide gas

Suffocation

Smothering—mechanical obstruction of nose and mouth

Plastic bagHandOverlying (can’t distinguish from SIDS)

Suffocation

Choking—requires an underlying explanation

IntoxicationNeurological disorderPsychiatric patient

Suffocation

ChokingAspiration of foodForeign objects

Suffocation

Mechanical asphyxia--compression of chest

Car/other heavy objectsBodies (riots, stampedes)Positional asphyxia

Cribs with mismatched mattressesIntoxicated adults

Suffocation

DrowningDry vs. wet drowningNeed to determine why person drowned

StrangulationExternal pressure causing closure of the blood vessels and tracheaPressures

4.4 lbs.—jugular veins11 lbs.—carotid arteries33 lbs.—trachea

Strangulation

HangingLigature Manual

Strangulation

HangingUsually suicidePoint of suspensionPOS superior to laryngeal prominence

StrangulationLigature

Usually homicideTransverse markEvidence of a struggle

Conjunctival petechiae Contusion of strap muscles Fracture of hyoid bone or superior horns of

thyroid cartilage

Strangulation—Manual

HomicideNeck 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 asphyxiaCyanide—almond odor

Cherry red discoloration of tissues

Carbon monoxide50% carboxyhemoglobin lethal levelCherry red discoloration of tissuesQuick (6 to 7 minutes)Children and elderly especially sensitive

Burns and Electrocution

BurnsCategories

FlameContactRadiant heatScaldingChemicalMicrowave

Burns

Rule of ninesHead—9%Arms—9% (each)Anterior torso—18%Back—18% Legs—18% eachNeck or perineum—1%

BurnsDegree 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 protectiveDeath

Immediate—smoke inhalationDelayed—sepsis from burns

BurnsMust establish

Identification of deceased Whether deceased was alive at the time of fireCause of deathManner of deathAny contributing factors

EtOH, drugs, natural disease

Burns75% 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)

BurnsWeight and height alteredFeet and hands may be lostPugilistic pose—shrinkage of muscleBody of an adult rarely destroyed by house or car fire

House fire temp—1200 to 1600 FCrematorium temp—1800 to 2000 F

Children may be consumed by fire

Burns

Artifacts of burnsEpidural hematomaFire fractures of bone

Burns

ScaldingImmersionSplashSteam

Burns

Chemical burnsAcids (HCL)Bases (lye, bleach)Petroleum products (blistering)

Electrocution

ElectrocutionOhm’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)

ElectrocutionCurrent Physiologic effect1 mamp Slight tingle16 mamp Release wire due to shock20 mamp Muscular paralysis 100 mamp Ventricular fibrillation2000 mamp (2 amp) Ventricular standstill5 amp Electrical burn20 amp Blows common h/h fuse

ElectrocutionLow voltage

Burns usually present at entry/exit sites Caveat—current entering over broad surface, e.g.

bathtub electrocution

Death due to ventricular fibrillation

High voltageElectrical burns—chalky white with crateringCharring Death due to ventricular standstill or paralysis of respiratory center

ElectrocutionLightning

Direct strikeSide flashconduction

Death from high-voltage direct current

Usually due to burns and injury to respiratory center of brain

Gunshot Wounds

Gunshot Wounds

Mechanics of firingFiring pin ignition of primer ignition of gunpowder creation/expansion of gas bullet, unburned powder, soot propelled down barrel of gun

Gunshot Wounds

Entrance woundsContactClose rangeIntermediateDistant

Gunshot Wounds

ContactMuzzle imprintStellate lacerations (if adjacent to bony structure)Gunpowder and soot enters wound

Gunshot WoundsClose range—within 3 inches

Increase in distance = increase in diameter of particle deposition and tattooing around entrance wound and decrease in particle densityEntrance wound

Particles of gunpowder around wound Soot on skin Tattooing of skin

Gunshot Wounds

Intermediate range—3 to 36 inchesFurther increase in diameter of particle deposition and tattooing around entrance wound and further decrease in particle densityNo soot

Gunshot Wounds

Distant range—greater than 36 inches

Absence of gunpowder particles, soot, tattooingDifficult to determine exact distance—appearance of GSW inflicted at 6 feet doesn’t differ from one inflicted at 16 feet.

Gunshot WoundsEntrance wounds

Usually smaller than exit wounds unless:Located adjacent to bony structures

(stellate)Bullet deflected prior to entrance

Inward beveling of skullRim of abrasion

Gunshot WoundsExit Wounds

Usually larger than entrance wounds due to deflection of bullet by tissuesOutward beveling of skullNo gunpowder particles, soot, tattooingNo rim of abrasion

Shoring of exit

Gunshot WoundsShotgun Wounds

Contact—circular wound with muzzle imprintClose

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


Mechanism—tearing, shearing, crushingCategories

ContusionAbrasionLacerationfracture

Blunt Force InjuriesContusion—hemorrhage into the soft tissue surrounding the wound

No bruise if blow from wide/smooth object or in area protected by heavy clothes/hairPatterned

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

Blunt Force InjuriesContusion

If death occurs quickly, no bruise evident—must incise area to detect hemorrhageColor change with time—from periphery to centerColor 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


ContusionVariables which increase bruising

Children and elderly • Senile ecchymoses on forearms of elderly

Obese women Alcoholics with cirrhosis Aspirin use

Blunt Force InjuriesContusions

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


Decomposed bodiesHemolysis of erythrocytes may mimic contusionsHemolysis of erythrocytes in genuine contusions also occurs—may be impossible to differentiate between decomp and contusion


Abrasion—scraping/removal of superficial layers of skin

Graze—bulletScratch—fingernail, sharp edgeBrush burn—frictional force (dragging on ground)Binding—handcuffs/rope


AbrasionPatterned

Weave of clothingThreaded pipeWood grain of baseball batgravel

Blunt Force InjuriesLaceration—blow from blunt objects or falls

Bridging of connective tissue within depths of woundAge determination difficultAppearance may not reflect object causing injuryIn general

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


LacerationExplore depths of wound for foreign materialDetermination of direction of wounding

abrasion/beveling—side from which blow delivered

Undermining of tissue—side away from which blow delivered

Blunt Force InjuriesFracture—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 InjuriesSkull 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


Skull fracture, baseBleeding from ears, nose or mouthHemorrhage into soft tissue of eyelids—raccoon eyesHemorrhage into soft tissue behind ears—Battle’s sign

Blunt Force InjuriesBrain 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


Intracranial hematomaSubarachnoidEpiduralSubdural


Subarachnoid hemorrhageMost common sequela of head traumaFocal or diffuseTraumatic

Laceration of veins—most common Laceration of internal carotid, vertebral,

basilar aa.

Blunt Force InjuriesEpidural hematoma—trauma to skull with rupture of artery at point of impact

Primarily impact injuries—falls, MVA’sBlood intervenes between dura and inner table skullA fracture is usually present—squamous-temporal bone

Blunt Force InjuriesEpidural hematoma

Usually confined to side of impactPresentation 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


Epidural hematomaDeath due to displacement of brain (mass effect) with brain stem compression

Blunt Force InjuriesSubdural hematoma—acceleration/deceleration injury

Stretching/tearing of bridging veinsMost common lethal injury from head traumaUsually not associated with fracturesMay occur in absence of obvious sign of trauma


Subdural hematomaAcute—symptomatic within 72 hrsSubacute—symptomatic between 3 days and 2-3 weeksChronic—symptomatic after 3 weeks


Onset of symptoms usually acute (30 minutes)

Life threatening at 50 mlDisplacement of brain (mass effect) with brain stem compression


Motor vehicle accidentsPatterned abrasions—steering wheelDicingSeat beltAortic transection distal to subclavian arteryFat embolism

Sharp Force Injuries


Stab woundIncised woundChop woundTherapeutic/diagnostic wound


Stab woundUsually homicideLength/depth of wound track > widthEdges usually without abrasion/contusion

Sharp Force InjuriesStab 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 InjuriesStab wound

Determination of angle Oblique angle—beveled margin on one

side/undermining of skin opposite side

Determination of edgeSingle edge—squared off edge/sharp edgeDouble edge—both edges sharp


Stab woundsMechanism of death

ExsanguinationTamponadeComplications (infection)


Incised woundLonger than deepNo bridging (differentiate from laceration)Usually suicidal

Hesitation marks/scars

Usually not fatal

Sharp Force InjuriesHomicidal incised—neck

Inflicted from behindBegins 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


Suicidal incised—neckInflicted from front

Short and angled Right handed—wounds on left side of

neck Slashes downward and medial at oblique

angle


Chop woundIncised wound with underlying injury to boneIncised and lacerated characteristics

Cutting and crushing


Chop woundAxeMacheteCleaverHoe


Therapeutic/diagnostic woundssurgical stab wounds

Chest tube Abdominal drain Thoracotomy/lapartomy incisions Cutdowns of wrist/antecubital fossae, Tracheostomy incision

Forensic Pathology - Dr

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