Download Forensic Pathology Review

Forensic Pathology
Matt Bowes, MD
Who is a forensic pathologist?
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BSc
MD
Anatomic pathology
Fellowship
A forensic pathologist is a doctor who
specializes in applying the science of
pathology to problems in the law
Where do I work?
• Forensic pathologists sometimes work in
hospitals
• In Nova Scotia we work in a new stand-alone
facility
What do I do?
• A forensic pathologist does autopsies, but that
is not all we do
The Golden Triangle
• The cause and manner of death may only be
known after a thorough investigation of three
things:
– The history
– The scene
– The autopsy
• This is called the Golden Triangle of death
investigation
The History
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This is the story of the dead person
What were they doing?
Who were they with?
How did they feel?
– What did they say, how did they behave?
• What diseases did they have?
The Scene
• Always important but especially so in the case
of:
– Deaths by asphyxia
– Deaths due to intoxication
– Any other death where anatomic lesions are
subtle or absent
Asphyxia
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Suffocation
Choking
Hanging
Strangulation
Mechanical and Positional
Chemical
Drug Deaths
• Anatomic findings are subtle to absent; death
scene may offer only clues to cause of death
The Autopsy
• The stepwise
examination of the
human body
• Invented in the early
19th century
• Same sequence in every
case
The Autopsy
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Evidence collection
External exam
Internal exam
Special techniques
Evidence Collection
• Can be anything you
can imagine, but is
commonly the
components of the
sexual assault kit
• Paint chips, fibres,
chemicals on the
surface of the body may
be important
The External Exam
• Identifying characteristics, such as tattoos or scars
• Signs of injury, such as abrasions, bruises, lacerations,
and injuries of other types
The Internal Exam
• The fundamental techniques have been the
same for hundreds of years
• The objectives may differ depending upon the
case, but documentation of the disease or
injury that is the cause of death is the
important one
Special Techniques
• Special cases call for additional techniques
• Examples:
– The rape kit (for example, where sexual assault is
known or suspected)
– The neck dissection (for example, where
strangulation is known or suspected)
– Soft tissue dissections (for example, where the
death occurred in custody)
Ancillary Testing
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Histology
Toxicology
DNA
Microbiology
What do I find?
Postmortem Changes
• The forensic pathologist is often confronted by
the findings that are typical of the decaying
body:
– Livor mortis
– Rigor mortis
– Mummification, putrefaction and autolysis,
adipocere formation
Livor mortis
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Also called postmortem hypostasis
Settling of blood with gravity
Deepens in colour with time
Initially blanchable, then fixed
Starts 30 min to 2 hours
Maximum and fixed at 8 – 12 hours
Rigor mortis
• Stiffening of the body after death
• Due to depletion of ATP, the actin and myosin
filaments become permanently complexed
• This remains until decomposition sets in
Autolysis and Putrefaction
• Other signs:
– Marbling
– Bloating
– Subcutaneous gas
– Purge
– Bullae formation
– Skin slippage
Adipocere
• “Grave wax”
• Due to saponification of fat
• Classically in cool wet conditions
Mummification
• Drying of body after death
• Often in the hands, nose, feet
• Drying of the eyes produces “Tache noire”
Patterns of Injury
Sharp Force Injury
• Incised Wound
– Length on skin greater than depth
• Stab Wound
– Depth greater than length on skin
Blunt Force Injury
• Contusion
– Force causes rupture of blood vessels and
bleeding into surrounding tissues
• Abrasion
– Scraping off of the epidermis
• Laceration
– Force (shear or crushing) causes tearing of tissue
Electrocution
• High Voltage
– >600-750 volts
– Electrothermal injury or cardiac arrest
• Low Voltage
– <600 volts
• VFib
Submersion in Water
The Snow Cone - DDx
• Remember that the snow cone has a
differential:
– Drowning
– Opiate intoxication
– Florid pulmonary edema in the setting of natural
death
Gunshot Wounds
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Contact Range
Intermediate Range
Indeterminate Range
Exit
Graze Wound