Forensic pathology

Forensic pathology is figuring-out why, when, where and how people died, if the manner of death is not obviously natural.

Manner of death

Manner

Homicide

Suicide

Natural

Accident

Undetermined

Notes:

• Undetermined - is a waste basket category.
• Homicide - not necessarily murder.
• Can be group into three:
  1. Intent to kill (homicide, suicide).
  2. No intent to kill (natural, accidental).
  3. Undetermined.

Cause of death

General

• The cause of death should be what started the sequence of events that lead to death.

"Word form"

Example:

• C. difficile colitis complicating antibiotic treatment for a dental abscess.
• Complications of laparoscopic cholecystectomy for ascending cholangitis with mesothelioma and atherosclerotic heart disease.

General forms:

• A complicating B for the treatment of C.
• A complicating B for the treatment of C with D and E.

WHO form

General form:

• 1a = immediate cause of death.
• 1b = what lead to the immediate cause of death.
• 1c... 1[x] -- where 'x' is the last letter used; 1x = What started the sequence of events.
• 2 = contributing factors.

Example 1:

• 1a. Ketoacidosis.
• 1b. Diabetes mellitus.
• 1c. Alcoholism.
• 2. Acute bronchopneumonia.

Example 2:

• 1a. Hemoperitoneum.
• 1b. Splenic laceration.
• 1c. Blunt force trauma.
• 2. Liver cirrhosis.

Natural deaths

• The cause should be a medical diagnosis, not the mechanism (e.g. cardiac arrest, cachexia, kidney failure).
• The mechanism is irrelevant.

Notes:

• Unnatural causes trump natural ones. If a guy with (nothing more than) a 70% proximal LAD stenosis and an old myocardial infarct is found in the water, they are usually called drowning.
• Cancer is rarely the immediate cause of death - it is usually something else.
• Things (mechanisms) that shouldn't be used: http://www.pallimed.org/2008/03/unacceptable-causes-of-death-other-web.html

Legal frame work

General

• In Ontario, the manner is determined by the coroner.
• Coroners, in Ontario, are MDs -- usually family docs.
• The cause (e.g. "gunshot wound to the head") is determined by the pathologist.

NB - the word coroner is not synoymous with MD. British Columbia has coroners that aren't MDs.

Case classification (Ontario)

Cases are classified as:

• A case = homicide and suspicious for homicide, (all) gunshot wounds.
• B case = adult, non-suspicious.
• C case = child, non-suspicious.

Notes:

• All A cases are done at regional centers by certified forensic pathologists.

Forensic triangle

Most general differential diagnosis:

• Natural:
  • Haemorrhage (e.g. cerebral bleed, gastrointestinal bleed, aortic aneurysm).
  • Infection (e.g. pneumonia).
  • Coronary atherosclerosis (cardiac arrhythmias - more common in the forensic context than myocardial infarction (MI); individuals with MIs don't usu. drop dead-- they go to the ER).
    • Post myocardial infarction (free wall rupture).
    • Ruptured (atherosclerotic) plaque.
• Toxic (memory device: PAIRO):
  • Poisons.
  • Alcohol (EtOH).
  • Illicit (e.g. cocaine, heroin, LSD).
  • Rx.
  • Over-the-counter (OTC) (e.g. acetaminophen, warfarin).
• Trauma (memory device AGE BS):
  • Asphyxial.
  • Gunshot wounds (GSWs).
  • Environmental (e.g. hypothermia, hyperthermia, drowning, lack of oxygen, electrocution).
  • Blunt force trauma.
  • Sharp force trauma.

Difficulties arise when more than one point of the triangle is in play, i.e. the forensic pathologist has to earn their pay when an old man with a heart condition is known to be into erotic asphyxia, and dies after doing some drugs and whilst indulging in erotic asyphxiation with a friend...

• If he had an arrhythmia and there was no stressor... natural death.
• If he over did it with the drugs, it is an overdose, ergo accidental.
• If he did the erotic asphyxia a bit too long it is accidental.
• If the friend held the plastic bag over his head just a bit long to asphyxiate him... it is a homicide.
• If he was a lone and depressed... he might have been trying to kill himself, ergo suicide.

Death-related changes

Rigor mortis

Definition:

• Muscle rigidity following death (caused by depletion of ATP).

Dependent on:

• Temperature of patient at death.
• Temperature variations in the environment since death.
• Presence of some medical conditions.
• May never develop!

It is the explanation for post-mortem goose bumps.

Summary

• Its onset & presence is highly variable.
• Forensic pathologists do not comment on time of death, as the above times are subject to such a large degree of variability, i.e. the estimates are essentially useless.

Time estimates

A crude guess for time of death based on rigor:

• Warm & flaccid <3 h.
• Warm & stiff 3-8 h.
• Cold & stiff 8-36 h.
• Cold & flaccid > 36 h.

Notes:

• Memory device: 3s: cut points are at 3 hours, 1/3 of a day, 3/2 of a day.

Livor mortis

Definition: pooling of blood in the dependent position, due to blood stasis.

• Onset may preceed death in the context of congestive heart failure.
• If pressure is applied to a dependent area-- no blood can enter there; thus, a pressure area is blanched (i.e. white).

• Can be seen externally, i.e. on the skin, and internally.
• Liver mortis becomes fixed some time after death.
  • Liver mortis does NOT tell one the position the decedent was in at the time of death-- only the position the decedent was at the time liver mortis became fixed. If the decedent wasn't moved liver mortis can help determine the position the person was in when they died.

Post-mortem decomposition/preservation

One of three things happens post-mortem:

1. Mummification.
2. Putrefaction (skeletonisation).
   • Green colour due to break down of hemoglobin (biliverdin).
3. Adipocere - transformation into wax (due to anaerobic bacterial hydrolysis of fat).

• A mix of the above often occur, i.e. part of the corpse is mummified... part of it decomposed through putrefaction.

Mummification:

• Predominant in dry environments.
• Body becomes dry and leathery.

Putrefaction:

• Body wet/moist after death -- ideal environment for putrefactive bacteria and organisms.

Artefacts

• Prinsloo and Gordon artefact = artefactual post-morten haemorrhage on the posterior surface of the esophagus.
  • Minimized by removing cranial contents & thoracic contents before undertaking neck dissection.
• Artefactual fractures (see fractures).
• Dilated anus (in isolation).
• Towel clip injury, usu. paired (in organ donors) - may be mistaken for an electroshock weapon (e.g. Taser) wound.
• Subclavian stab for vascular access - may be confused with a gunshot exit wound.

Infants

• Lumpy neck - small superficial nodules on anterior neck ~2-5 mm (???).
• Intussusception of small bowel - often multiple.

Wounds

Classification (gross pathology)

Mnemonic CALI:

• Contusion - "bruise", haematoma.
  • Age (usual colour change sequence): red, blue, green, yellow, brown.
  • Etiology: bleeding from arterioles or venules (not capillaries).
• Abrasion - "scrape", e.g. motorcyclist slide across the roadway... skin scraped-off.
  • Can be subclassified as brush abrasions (has skin tags) and crush abrasions (do not have skin tags).
    • Skin tags suggest directionality; they are found at the distal point / point of last contact.
• Laceration - "tear", indicates blunt force trauma; contact point may be distant from where skin splits.
• Incised - "cut", e.g. caused by a knife.
  1. "Cut" or "slash" = length > depth.
  2. "Stab" = depth > length.

DDx

How to decide what you're looking at:

• Contusion:
  • Can be demonstrated histologically... there are extravascular RBCs.
    • If pre-morten there is vital reaction, i.e. WBCs come to clean-up the trauma.
  • If the post mortem interval is not known and long-- differentiation from decomposition may be non-trivial/impossible.

• Abrasion vs. contusion:
  • Contusions skin is intact... in abrasion it is not.
  • Abrasions and contusions may be co-localized, i.e. in the same place.

• Laceration vs. incision:
  • Lacerations have "bridges", incisions do NOT have bridges.
    • Bridges are fine strands of tissue that cross the long axis of the skin defect.
      • You can think of the wound as partially "sutured" by the bridges of tissue.
  • Lacerations are usually associated with a contusion and/or crush and have an irregular margin.
  • Lacerations are classically on the skull and face. They are rarely on the abdomen.

Dating

• Colour is somewhat useful for bruises.
• Post-mortem injuries tend to be orange-yellow.

Microscopic

Wounds can be grouped into:

• Pre-mortem.
• Post-mortem.

Signs a wound was inflicted during life:

• Blood.
  • Hypostasis/decomposition can mess with this, i.e. blood oozing out of vessels post-mortem shouldn't be called an injury.
  • Hemosiderin demonstrated by an iron stain - hard sign.
• Inflammation:
  • PMNs 6-24 hours after injury.
  • PMNs replaced monocytes in 24-48 hours.

Fractures

Artefactual

• "Undertaker's fracture" - cervical fracture due to rough handling.
• Basal skull fracture due to opening of skull.
  • Classically does not cross sella turcica.
  • Notably absent features of a real (ante-mortem) fracture: hematoma, brain injury.
  • Mechanism to explain trauma not present in history; a fall/tripping not sufficient.

Healing

• Osteochrondral reaction - early.

Child abuse-related

• Paravertebral nodules = classic location for rib fractures in child abuse.
• Metaphyseal fractures - "classical metaphyseal lesions".

Healing

Simplified classification:

• Primary callus (cartilaginous) - early.
• Secondary callus (bone) - late.

Notes:

• Radiology is not good at dating fratures, but good at finding 'em.

Motor vehicle vs. pedestrian

If the pedestrian is standing during the initial impact one classically finds, at bumper level, a lower limb fracture with a Messerer wedge (German: Messerer-Kiel); the wedge points in the direction of the (impact) force.

Autopsy

Main article: Autopsy

The autopsy article covers procedural things. Heart dissection is covered in the heart article.

Types

Forensic vs. hospital:

• Forensic autopsies are focused on the external exam.

Marking conventions for common findings

There are no universal marking conventions for injuries.

One system in use (the Rose system) is:

• One red line for an incised wound.
• Multiple closely spaced red lines, i.e. red hatching, for abrasions.
• Multiple closely-spaced blue lines, i.e. blue hatching, for contusions.

The above makes sense in that:

• Abrasions and incised wounds typically bleed - are red.
• Contusions (bruises) don't classically bleed and are classically blue.

External exam findings

Colour of the corpse:

• Red (Pink) = carbon monoxide, cyanide, fluoroacetate.
• Purple (intense) = propane.
• Green = hydrogen sulfide.
• Brown = nitrites (methemoglobinemia).

Autopsy terminology

• Gutter butter = adipose tissue in a decomp case; looks like butter topping put on popcorn. A Toronto-ism.
• Gutter blood = blood in the empty thorax - after extraction of the organ block.
• Tardieu spots = postmortem hypostatic hemorrhages; look like large petechiae - in dependent areas.

Autopsy on decomposed remains

General

• AKA "decomp autopsy" or simply "decomp".
• Histology usually very limited or useless.
• Often done to exclude trauma.
• Typical scenario: decedent lives alone -- body not discovered for prolonged period of time.
• More likely to be a negative autopsy than non-decomp cases.

Suspicious decomp

Common sense rules for if skin is not intact:

1. Blunt dissection (to avoid artefactual injuries to the bones).
2. Clean the bones (not with bleach)
   • Bones cooked for 1+ hours... with frequent checks to avoid that they become mushy.

Environmental

Includes:

• Hypothermia.
• Hyperthermia.
• Drowning - see asphyxial deaths.
• Lack of oxygen - see asphyxial deaths.
• Electrocution.

Hypothermia

Features:

• Reddening of exposed skin areas "frost erythema" - classic feature.
• Wischnewski spots - classic feature.
  • Brown/black spots of the gastric mucosa ~ 0.1-0.4 cm; thought to represent pre-mortem/perimortem hemorrhage.
• Paradoxical undressing; decedent has removed clothes due to perception of being too hot.

Notes:

• Findings are often non-specific.
• Non-specific findings seen in hypothermia:
  • Pulmonary edema.
  • Hemorrhagic pancreatitis.
  • Hemorrhage of the iliopsoas muscle.
• DDx of reddening of skin includes carbon monoxide poisoning.

Image:

• Wischnewski spots (springerlink.com).

Hyperthermia

Features:

• Findings are non-specific.
• Short survival:
  • +/-Petechiae - serosal (pleural, epicardial, pericardial) and cerebral periventricular.
  • +/-Cerebral edema.
• Long survival:
  • Findings consistent with hypovolemic shock (hepatic necrosis, cerebral edema, DAD in lung, acute pancreatitis).
  • Clinical/biochemical: rhabdomyolysis, DIC, ATN.

Electrocution

General:

• May be missed - as can be subtle.

Gross features:

• Usually burns on the hands - brown.

Microscopic features:

• Palisading of basal cells (like cautery artefact).

Gunshot wounds

Main article: Gunshot wounds

Gunshot wounds (GSWs) are a relatively uncommon finding in Canada. They are dealt within a separate article.

Asphyxia

Main article: Asphyxial deaths

• This is a big topic and covered by a separate article.

Classification

• Strangulation - where there are signs of neck compression.
  • Includes: ganging, ligature strangulation and manual strangulation.
• Chemical asphyxia - usually no signs of neck compression.
  • Includes: carbon monoxide poisoning.
• Suffocation - usually no signs of neck compression.
  • Includes: Smothering, choking, positional asphyxia, drowning.

Blunt force trauma

General

• Weapon: fist, foot, baseball bat... pretty much anything.
• Beer bottles are common... and strong enought to fracture a skull.
  • Empty bottles have a higher fracture energy than full ones.

Commotio cordis

Features:

• Often negative autopsy; no cardiac pathology.
• Etiology: arrhythmia.
• History: trauma to chest.

Note:

• May be spelled Commodio cordis.

Motor vehicle collisions

• Pedestrian vs. motor vehicle: heel to injury measurement.

Seromuscular tear

Features:

• Intestinal injury associated with motor vehicle collisions and more specifically seatbelts.
• AKA seatbeat syndrome.
• Def'n: separation of inner muscularis from submucosa.

Descent from height

• Relatively common way to suicide.
  • May be an accident, e.g. decedent thought they can fly (due to a psychosis).
  • May be a homicide, e.g. decedent was pushed.

Gross

Features:

• Multiple injuries - often including multiple fractures, e.g. basal skull fracture, flail chest.
• +/-Haemothorax - can be proved with a large bore needle.
  • Sufficient for cause of death - can be used to do an abbreviated post-mortem.
• +/-Haemoaspiration (due to facial trauma) - presence suggest that decendent was alive shortly after landing/impact and thus likely very alive during the descent.
  • Patchy red centrilobular spots on gross examination.

Trauma with delayed death

• Epidural hemorrhage - lucid interval.
• Subcapsular splenic hematoma with subsequent rupture.
• Subcapsular hepatic hematoma with subsequent rupture.
• Aortic dissection with subsequent rupture.

Sharp force trauma

Characteristics

• Incised wound (see: Classification of wounds).
  • "Clean" edge (no contusion, no abrasion).
  • Well-demarcated edges.

Subclassified into cut/slash and stab (see: Classification of wounds).

Weapons

• Knife.
• Scissors - classic "Z" shape.
• Screwdriver.
• Glass.

Aortic trauma

• Aortic dissection due to trauma is often catastrophic.
• Classic location of injury is subclavian branch point.

Dissections often classified as:

• Type A - aortic root to just distal of left subclavian artery.
• Type B - distal to (left) subclavian artery.

Head injuries

Accidental vs. intentional

Features of non-accidental injuries:

• Lacerations:
  • More than three.
  • Length >= 7 cm or more.
  • Location:
    • Above hat brim line (HBL).
    • Ear.
    • Left-sided.
• Fractures:
  • Comminuted or depressed calvarial fractures.
  • Location:
    • Fractures located above the HBL.
    • Left-sided fractures.
    • Facial fractures.
• Contusions:
  • Greater than four facial contusions.
• Other:
  • "Postcranial osseous" [sic] (non-rib, non-skull) and/or visceral trauma.

Note: The paper doesn't give odds ratios for the the different features -- like in the rational clinical exam series... it is a shame.

Diffuse axonal injury

Clinical:

• Vegetative state.
• Imaging findings: no anatomical cause apparent (in some cases).

Etiology:

• Hypothesized to arise from high shear loading of white mater tracts.

Macroscopic findings:

• Tears - corpus callosum.
• Haemorrhage.

Microscopic findings:

• Axonal retraction balls.
• "Microglial stars".
• Degeneration of fibre tracts.

Grading:

• Grade 1: only microscopic findings.
• Grade 2: ?
• Grade 3: macroscopic and microscopic findings.

IHC: beta-amyloid precursor protein (beta-APP or APP).

Intracranial hemorrhage

Main article: Intracranial hematoma

Classification:

• Epidural hematoma.
• Subdural hematoma.
• Subarachnoid hematoma.

Traumatic brain injury in infants

Main article: Traumatic brain injury in infants

• Shaken-impact syndrome.
• Shaken baby syndrome.

Commotio medullaris

Features:

• Sudden death after head trauma that is insufficient to explain death.
• Etiology: unknown - thought to be related to apnea.
• Analogous to commotio cordis (see blunt force trauma).

Excited delirium

General:

• Also known as "agitated delirium".
• Dx is considered controversial, especially outside of the forensic pathology community.
• The diagnosis has garnered considerable attention in the context of electroshock weapon use, as Taser International (a manufacturer of electroshock weapons) has blamed all deaths involving its weapons on it.

• There is no "official" definition for excited delirium.
  • Most agree it includes fever.

One paper defines it in relation neuroleptic malignant syndrome:

• Fever.
• Disorientation and confusion.
• Increased energy/superhuman strength.

Excited delirium - hypothesis:

• Thought to arise in the context of severe chronic mental disorders (e.g. schizophrenia) and protracted cocaine binges.
• Thought to result from alteration of dopamine receptor density. The D2 receptor in particular, which is thought to be important in temperature regulation, is decreased in psychotic cocaine abusers.

Toxicology & biochemistry

General

Things usually collected at autopsy:

1. Blood in EDTA tube (genetic testing).
2. Urine toxicology:
   • Useful to evaluate myoglobin.
3. Vitreous:
   • Biochemistry.
   • Ketones.
   • Urea (???).
4. Bile:
   • Acetaminophen overdoses.
   • Opiate overdoses.

Myoglobin DDx:

• Neuroleptic malignant syndrome.
• Malignant hyperthermia.
• Serotonin syndrome.

Biochemistry

• Diabetes:
  • Plasma:
    • Hemoglobin A1c - increased.
    • Acetone - increased.
    • Beta-hydroxybutyrate - increased.
      • Also increased in alcoholic ketoacidosis (though ketones low).
  • Urine:
    • Aceto-acetate - increased.

Death by insulin overdose:

• C-peptide - low.
• Insulin - high.

Serum

• Potassium - rises quickly and rapidly after death; completely useless.
• Sodium - tends to decrease after death; usually useless.
• Glucose - drops quickly; useless unless sky high.
• Urea, creatinine and urate - stable for ~48 hours post-mortem.

Vitreous

• Creatinine and urea - approximate those at time of death.

Toxicology

• Should be submitted with anatomical findings and history.

Common submissions:

1. Alcohol only.
2. Suspected toxicologic death - need details on drugs.

Mandated by case

• Sudden death in children under five years old.
• Workplace deaths.
• Fatal motor vehicle collision.
• Aviation deaths.
• Fire-related deaths (carboxyhemoglobin).

Toxins

Ethanol

• Usually measured (in Canada) as: mass of EtOH (mg)/volume of blood (mL).
  • Limit (Ontario): 80 milligrams of alcohol in 100 millilitres of blood (0.08 gm/100 mL).
  • Enough to be fatal ~ 350 mg/dL ~= 76 mmol/L.

Ethanol intoxication as a table

	Concentration	Concentration	Concentration	Concentration
Legal limit - Ontario	80 mg/dL	~17 mmol/L	0.8 g/L	0.08 g/dL
Mild	< 180 mg/dL	< 39 mmol/L	< 1.8 g/L	< 0.18 g/dL
Moderate	180-350 mg/dL	39-76 mmol/L	1.8-3.5 g/L	0.18-0.35 g/dL
Severe	350-450 mg/dL	76-98 mmol/L	3.5-4.5 g/L	0.35-0.45 g/dL

Notes:

• 1 mg/dL = 1/4.607 mmol/L.
  • Ethanol's molar mass = 46.07 g/mol.

Cocaine

• No agreed upon toxic dose - due to tolerance.

Features (see: cocaine toxicity):

• Usually anatomically normal heart.
• +/-Advanced atherosclerosis for age.
• +/-Infarction.
• +/-Contraction band necrosis.
• +/-Cardiac hypertrophy.

Ethylene glycol

For a more general discussion see urine crystals

• Not done in routine toxicology screening.
• Birefringent calcium oxalate crystals found in kidney (with polarized light).

Anaphylaxis

Serology:

• IgE.
• Tryptase.

Natural death

Main article: Natural death

There is a lot that can kill ya... but only a few of those are quickly, i.e. within a hour or so.

Generally, these things are:

• Cardiovascular:
  • Arrhythmia.
  • Myocardial infarction.
  • Haemorrhage.
    • Ruptured aneurysm.
  • Hypertensive heart disease.
• Respiratory:
  • Pulmonary embolism (PE).
  • Asthma.
• GI:
  • Haemorrhage.
    • Esophageal varices.
    • Gastric varices.
• Neurologic:
  • Intracranial haemorrhage.
    • Ruptured aneurysm.
    • Spontaneous subdural haemorrhage.
  • Stroke:
    • Haemorrhagic.
    • Thrombotic (more common than haemorrhagic).

Forensic entomology

Main article: Forensic entomology

• Study of the bugs that eat corpses.
• Bugs may hide a wound... it is important to know where they like to be.

Forensic anthropology

Main article: Forensic anthropology

Forensic anthropology is looking at skeletal remains. It may be useful of identification and, rarely, the cause of death. Important in skeletonized remains and decomp cases.

Forensic taphonomy

• The study of post-mortem decay to assist in a medicolegal investigation.
  • Taphonomy = postmortem fate of biological remains; derived from the Greek word taphos (grave).

See also

• Forensic entomology.
• Autopsy.
• Heart.

External links

• Forensic pathology (cap-acp.org).
• Fractures (drexelmed.edu).

Post-mortem changes

• Post-mortem changes (emedicine.medscape.com).
• Post-mortem changes (the-crankshaft.info).