Module 3 - Forensic Pathology

FRSC1030 FRSC pathology

Pathologist:

medical doctor who investigates and studies disease in humans

Forensic pathologist

a pathologist who studies disease and trauma leading to death

What is Forensic Pathology?

branch of medicine for legal purposes and concerned with examining/determiningcause of death, injuries due to crime and negligence, and tissue samples relevant to crimes

Autopsy largely synonymous w/…..

forensic pathology.Term a combination of Greek terms “autos” (self or with one’s own) and “opsomei” = “seeing with eyes” thus “autopsy” means “seeing with one’ s own eyes.

Death Investigative Systems • Differs by….

political jurisdiction

Death Investigative Systems (2 general systems)

Medical Examiner System:, Coroner System:

Medical Examiner System:

physician trained in pathology and forensic pathology (AB, MB, NF, NS)

Coroner System:

investigators of unusual or suspicious deaths (BC, NB, ON, PE, QC); normally, no formal training required (ON: need to be a physician)

Office of the Chief Coroner Ontario Forensic Pathology Service investigate death when:

-appears from unnatural causes -natural deaths if sudden/unexpected -concerns re: care prior to death -mining/construction, police use of force, incarcerated

Office of the Chief Coroner Ontario Forensic Pathology Service determines what

who (identity of deceased) • when (date of death) • where (location of death) • how (medical cause of death) • by what means (natural causes, accident, homicide, suicide or undetermined)

Cause of Death Divided into primary and secondary causes (3)

1. Most recent condition 2. Next oldest condition 3. Oldest (original/initiating) condition

Manner of Death Abbreviation

NASH

Manner of Death (NASH) Five outcomes:

homicide -suicide -accidental -natural -undetermined

Autopsy - Documentation

-photos with/without clothing

-type of clothing -location and type of trauma (e.g., location of bullet wounds; entrance and exit wounds)

-defensive wounds

-collect evidence from external examination and clothing

-note: age, gender, height, weight, physical condition, abnormalities

-rigor-, livor- and algor mortis

Classification of Trauma

Mechanical, Chemical (e.g., acid), Thermal, • Electrical • Radiation • Blast

Classifications of Mechanical Trauma

- Sharp force - Blunt force - Gun shot -Asphyxia

1. Sharp force

-often death by exsanguination

2. Blunt force

-often death by brain damage -commonly creates contusions (accumulation of blood outside normal blood vessels) where impact weapon may leave a distinguishable pattern - extreme contusions are hematomas (bigger pockets of blood) and can help explain context of death

3. Asphyxia – 3 main mechanisms

- suffocation, strangulation, chemical (e.g., CO)

Low-voltage electrical injury; can lead to…

ventricular fibrillation (heart quivers, but does not pump blood).

-High voltage electrical injury heart will become…

defibrillatory (stop beating) and cannot be resuscitated-

Petechiae

Red or purple spot on body, caused by a minor hemorrhage (broken capillary blood vessels)

Petechiae Sometimes associated with…

strangulation if present in eye, but not conclusive as also associated with other conditions (e.g, heart attack)

Pathology can help investigations but…Caution in…

Conclusions!

Skin discoloration caused by…

carbon monoxide poisoning

Quantitatively estimating PMI within an accurate time frame is….

crucial (but lots of challenges/assumptions)

Various methods used in field to estimate time since death;

Temperature; Rigor Mortis; Entomology; Decay

Active transport:

mechanism that transports molecules and other substances across membranes

Active transport requires expenditure of….

cellular energy (ATP) to move molecules against a concentration gradient

When an organism dies active transport ceases due to…

loss of cellular energy that is required for the process

When selective membrane permeability is lost, analyte concentrations across barriers approach….

equilibrium values

Rigor Mortis:

Stiffening of body after death muscle membranes become more permeable to Ca2+ (muscles contract)

Rigor Mortis: -Begins _____ after death, remains…

2-6 hours, 2-3 days

Livor Mortis:

(lividity)settling of blood no longer circulating, gravity (purple)

Livor Mortis: Begins about _____ after death (unless ______)

1 hr, poisoned by CO

What is this an example of …

rigor mortis

What is this an example of …

Livor Mortis:

Algor Mortis:

decrease in body temperature after death

Glaister equation:

linear relationship of anal temp/time -1.5 C/hr (2C during 1st hr, 1C per hr nearing ambient T)

Pallor mortis:

change in tone of skin occurs within 15–25 min after death

Pallor mortis: little to no use in….

TOD, occurs too quickly from lack of circulation of blood

Algor, Rigor and Livor Mortis what can impact these ?

Disease Drugs/Poison (CO) Weight\ Surface Area Ambient temp Environmental Conditions Conductivity of medium body on

Vitreous Humour : Estimate PMI using….

analyte concentration in vitreous humor

Vitreous Humour

gelatinous fluid between lens and retina of eye

Vitreous Humour: Through diffusion from retina the potassium ion (K+ ) concentration…..

increases predictably with time after death

Several factors have been shown to decrease strength of correlation between [K+] and PMI (3)

– Environmental and ambient temperature – Antemortem conditions – Cause of death

What also impacts K+ concentration

• Death from drug overdoses/chronic illness = extremely variable K+•

Individuals with burn injuries - higher K+ levels than expected.

K+ concentration alone to estimate PMI yields……

wide interval

K+ ions analyzed simultaneously with other analytes found in vitreous humor to increase accuracy of….

PMI estimate (e.g., Sodium (Na+ ), ammonium (NH4 + ) and barium (Ba2+))

Internal Examinations and Dissection

Remove, weigh and examine internal organs

• Look for signs of disease -coarse visual and histology

• Stomach contents examined • Small intestines (undigested portions) examined
• PMI (temp of body and organs)

• MANY OTHER ASPECTS LIKE TOX in next section….

Traditional postmortem examination can be traced back….

700 years to its beginnings in Italy

Traditional autopsy begins with a…

deep Y-shaped incision in chest. Next, skin is peeled back to expose rib cage, must be sawed open with bone cutter so various organs can be removed and examined.

Characteristics of Autopsy:

• Usually invasive/destructive.

• Time consuming.

• Can be subjective (see Gouge Inquiry!)

• May lead to loss of evidence.

Virtopsy

non-invasive imaging, scans entire body and captures 2D and 3D images; generates same conclusions as hours of classical autopsy

term virtopsy created from terms….

virtual and autopsy: “virtual” in ancient Latin means “useful”.

Virtopsy Provides objective documentation to analyze….

process of physical features and evidence.

Virtopsy: combination of…

C.T. (Computed Tomography), M.R.I. (magnetic resonance imaging) and 3-D surface- scanning technology.

MSCT stands for…

Multi-Sliced Computed Tomography derived from the traditional CT scan (Computed tomography) or CAT (computed axial tomography) scan

MSCT consists of……

a rotating X-ray supply that spins around a patient at an extremely high speed. Directly opposite to this X-ray is an array of the X-ray detectors that also rotate at exactly the same rate. As ring rotates around patient, X-rays are emitted, and detectors capture images.