Forensic pathology

Forensic pathology is figuring-out why people died... along with when and how (if possible).

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.

Example:

• C. difficle colitis complicating antibiotic treatment for a dental abscess.
• Complications of laparoscopic cholecystectomy for ascending choleangitis 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.

Natural deaths

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

Notes:

• 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
• A Nice summary: http://www.eperc.mcw.edu/fastFact/ff_155.htm

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).
  • 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

Def'n: 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!

Summary: Its onset & presence is highly variable. Therefore, it is only marginally useful for determining the time of death.

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

Def'n: 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.

Decomposition

According to textbooks one of two things happens post-mortem:

• Mummification, or
• Putrefaction.

Real life:

• A mix of mummification and putrefaction 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.

Classification of wounds

Mnemonic CALI:

• Contusion - "bruise", haemotoma
• Abrasion - "scrape", e.g. motorcyclist slide across the roadway... skin ripped-off
• Laceration - "tear", trauma distant from where skin split
• Incised - "cut", e.g. caused by a knife.
  1. "Cut" or "slash" = length > depth.
  2. "Stab" = depth > length.

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.

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.

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

• 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.

Sharp force trauma

• Knife or other sharp object.

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

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

Cocaine

• No agreed upon toxic dose - due to tolerance.

Features (see: cocaine toxicity):

• Chronic is characterized by advanced atherosclerosis for age.
• +/-Infarction.
• +/-Cardiac hypertrophy.

Ethylene glycol

• 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.
• 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

It is looking at skeletal remains. It may be useful of identification and, rarely, cause of death.

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).
• Post-mortem changes (emedicine.medscape.com).
• Fractures (drexelmed.edu).