Forensic Pathology
Chapter 10
Pathology: Study of structural and morphological changes to the body as a result of a disease state. (AKA anatomic pathology)
Anatomic pathology
Clinical pathology
Forensic pathology
Clinical Pathology: Analysis of materials/fluids removed from the body.
Blood, saliva, sperm, urine, spinal fluid, etc.
Most clinical pathology work is now done by forensic toxicologists and consults with a forensic pathologist.
Forensic pathology helps determine the cause and manner of death in suspicious or unexplained deaths.
It takes about 13-14 years to become a forensic pathologist.
1. Determine apparent cause of death.
2. Determine the time of death or PMI.
3. Ascertain the manner of death.
4. Determine the identity of the deceased individual.
Duties Include
Coroner System: Does not need a medical background.
Two systems of death investigation:
Medical Examiner: Must be a physician.
PMI = Postmortem interval
Time since death
The death certificate must be signed by an attending physician, medical examiner, or coroner.
Cause of Death: The disease, trauma or injury which results in death.
Stroke
Car accident
Drowning
Stabbing
There may be secondary cause in addition to a primary cause.
Manner of Death: Set of circumstances that exist at the time the death.
All deaths must be assigned to one of four for five categories even if it is an educated guess.
Manners of Death
1. Homicide
2. Natural cause
3. Accidental
4. Suicide
5. Undetermined
Autopsy = “to see with one’s own eyes”
Next of kin must give permission for an autopsy unless it is ordered by law through the medical examiner or coroner.
An external examination of the body is done first.
Things noted might include:
Identifying marks (birthmarks, tattoos)
Clothing
Defensive wounds
Bruising
Photos of the body clothed and unclothed are taken
Internal Examination
Things done include:
Body fluid samples are taken
May include x-rays
Remove major organs to weigh and measure them.
Trace the path of penetrating injuries and removal of materials such as bullets.
Patterns of Injury and
Classification of Violent Deaths:
Mechanical
Gunshots
Falls
Vehicle accidents
Blunt force trauma
Stabbings
Incisions
A sharp instrument will cause an incision. Notice the sharp edges.
Lacerations
A blunt force injury causes lacerations. Lacerations have rough edges.
Gunshot wounds are considered a blunt force injuries.
High speed bullets (Hunting and military rifles) cause more damage than lower speed bullets (Hand guns).
Gunshot wounds are divided into 3 types:
Entry wound shows blackening and swelling due to hot gases injected under the skin.
The swelling often causes lacerations
in the skin.
Imprint showing the shape of a firearm muzzle and sight.
Stellate hard contact wound of the head. Note the abundant soot in the wound depths.
Distinctive mark from a hard contact wound due to a shotgun with a muzzle brake.
feet of the target)
Shows stippling around the wound - particles of unburned and partially burned propellant lodged in the skin.
The diameter of the stippling ring is proportional to the distance of the gun from the target.
Stippling and soot deposition surrounding a gunshot wound.
Stippling (tattooing) surrounding gunshot wound.
feet from the target)
In distant wounds the target is far enough away that the stippling doesn’t reach the target or falls off when it hits.
Distant entrance wound due to high-velocity rifle. Note the absence of residues surrounding the wound and the presence of hexagonal abrasion rim.
Entrance wound with an eccentric abrasion rim indicating that the bullet struck the skin obliquely. In this case, the bullet was traveling in an upward direction.
Close-range shotgun wound. This photograph shows a single defect with ragged, scalloped edges and a few satellite defects.
Slightly more distant shotgun wound. This photo shows a large, dominant, central defect with smaller satellite defects surrounding it.
Distant shotgun wound with multiple, evenly distributed discrete defects due to birdshot.
Radiograph of a high-velocity rifle wound. Note the extensive fragmentation of the projectile.
Thermal
Hyperthermia
Hypothermia
Heatstroke, fevers, burns, hot gas inhalation, etc.
Frostbite or low core body temperature.
May not show outward signs unless burns are visible or there are signs of frostbite.
Alcohol dilates blood vessels and increases heat loss. Intoxicated individuals are also less sensitive to heat and cold and may not perceive dangerous temperature levels.
Electrical
An alternating current of moderate voltage (< 1,000 volts) can cause ventricular fibrillation (heart quivers uncontrollably).
High voltages stop the heart by disrupting impulses. It can cause severe burns in just seconds and the destruction of cellular material in the body.
Voltage is the potential gradient between 2 sites, generally considered high voltage above 500-1000 V. For comparison, most household appliances work at 110 V. The image shown demonstrates grounded sites of low-voltage injury in the feet.
Low-voltage burns are mostly thermal burns caused by prolonged contact; usually at least several seconds of contact are required. They almost exclusively occur in the hands of adults and in the mouths of children. Children may chew on extension cords and receive an oral burn when the protective coating is worn away. The image shown shows the energized site of a low-voltage electrical burn in a 50-year-old electrician.
On a cellular level, electrical burns may show elongated pyknotic keratinocyte nuclei with vertical streaming and homogenization of the dermal collagen, as shown in this 40× histology slide.
Chemical
Drugs and alcohol contribute to death far more often than cause death.
Drugs that cause death are most commonly depressants.
Cocaine is a stimulate and can cause seizures and uncontrolled heart beating.
Synergism of drugs may also result in death.
This is when two or more drugs magnify each other’s effects so they may result in death even though either dose of the drug by itself would not be lethal.
This type also includes carbon monoxide poisoning
CO levels as low as 20% can kill.
Levels of 90% is not uncommon for people trapped in fires.
Cyanide poisoning has a characteristic odor of almonds.
Postmortem Interval (PMI)
Determining PMI is an important part of a death investigation.
Cannot be determined exactly.
Investigation of the PMI begins at the death scene.
Potassium levels in the eye can be used to plot death during the 1st 24 hours.
Algor mortis, livor mortis, and rigor mortis are all used to estimate an early PMI of up to 48 hours.
There are well established guidelines for each of these processes but they may vary according to the temperature and environment of the deceased.
If the deceased has been dead several days, weeks, or longer, then other methods must be used to determine the time of death.
These may include the degree of composition of the body and the activities of insects on the body.
Algor Mortis
Cooling of the body
Temperature will decrease until it meets the ambient temperature.
If the ambient temperature is above the normal body temperature then the temperature will rise.
The average rate of cooling is 1°-1.5° C an hour and will vary due to several factors:
Ambient temperature
Enclosed area (e.g., car, embedded in cement) vs. Open area (i.e., outdoors).
Body size (a small / thin body will lose heat much faster than a large / heavy body), which is also related to body composition (more or less fat).
Amount and type of clothing (due to insulation).
Livor Mortis
Starts 20 minutes to 3 hours after death and is congealed in the capillaries in 4 to 5 hours. Maximum lividity occurs within 6-12 hours.
A reddish discoloring of the body due to the settling of blood as a result of gravity.
White patches are due to compression of body tissue by the weigh, which keeps the blood from entering those tissues.
Maximum lividity occurs within 6-12 hours.
Rigor Mortis