Introduction to Forensic Pathology

Question 1

What is the cause of death vs manner of death vs mechanism of death?

Answer 1

Cause of death - the underlying mechanism which set forward the mechanism of death: i.e. atherosclerosis

Manner of death - natural vs suicide vs homicide vs accident

Mechanism of death - Physiologic abnormality which is incompatible with life i.e. cardiac arrhythmia, respiratory depression, sepsis, etc

Question 2

What is lividity (livor mortis) and when does it begin? When is it permanent? Where does it not occur?

Answer 2

Begins 30-45 minutes after a death, a pooling of blood in the direction of gravity. Permanently in place within 8-12 hours, and is never reversible afterwards. Before that, there is blanching

Does not occur in areas of pressure

Question 3

What are tardieu spots?

Answer 3

Small spots where the capillaries rupture due to increased pressure from the lividity, leading to blue-purple areas of hemorrhage

Question 4

When does rigor mortis occur / peak? When does it decline? What is one component of rigor mortis relating to hair you might not think about?

Answer 4

Starts shortly after death, peaks after 8-12 hours, and slowly passes after 24 hours. Goosebumps after death -> arrectores pilorum

Body which is greater than 1 day old will have no rigor mortis but livor mortis.

Question 5

What is Algor mortis?

Answer 5

Postmortem cooling of the body

Question 6

What might look like antemortem abrasions and what is the process by which they are formed?

Answer 6

Superficial skin lesions w/ irregular borders -> ant / roach bites, as insects feed on epidermis

Question 7

What is a contusion vs abrasion vs laceration? What causes them?

Answer 7

All are from blunt-force trauma

Contusion - Bruise

Abrasion - Scrape

Laceration - Elastic tearing of skin due to blunt force

Question 8

How does a laceration differ from a cut and what is a dead giveaway?

Answer 8

Laceration - caused by blunt-force trauma, pounding of the skin will lead to tearing of the skin, but bridging structures (vessels and nerves) with greater tensile strength may stay intact. The wound will often have jagged edges and a surrounding abrasion. A contusion will be associated with area of trauma.

Cut - Very clean, caused by sharp-force trauma, bridging structures will be sliced, and there will be no contusion

Question 9

What do bruises of different ages suggest in adults and children?

Answer 9

Adults - Repeated falls, common in alcohols and individuals with dementia / arthritis

Children - Child abuse

Question 10

What causes a coup / contracoup injury and what is this useful for determining?

Answer 10

Coup - impact of brain directly with a surface (i.e. frontal lobe if you bang the front of your head). Less severe, usually only if you have a skull fracture at that spot.

Contracoup injury - more severe and opposite the coup injury, from kickback of brain in cranial cavity, only happens in falls and not blunt force trauma (i.e. occipital lobe if you bang the back of your head)

Question 11

What is a brush burn?

Answer 11

A type of abrasion caused by dragging a body on a paved surface

Question 12

What happens in adults and children in a front impact collision? What type of injury is this?

Answer 12

Primary injury

Adults - struck by bumper below center of gravity, flung onto the windshield
Children - struck by bumper below center of gravity, knocked into roadway

Generally, bruises, lacerations and fractions of the lower extremities will be seen

Question 13

What are two other types of collisions other than front impact?

Answer 13

Sideswipe collisions - no direct bumper contact

Runover collisions

Question 14

What is the most common site of an overstretching injury?

Answer 14

Pedestrian is struck from the rear causing over-stretching injuries / superficial tears of the groin

Question 15

What are secondary / tertiary injuries to pedestrians?

Answer 15

Secondary - Caused by impact with hood, windshield, or A-pillar of car

Tertiary - gravel or brush-burn injuries as they are dragged or thrown to the road surface. Common on protuberant areas

Question 16

What two things are very useful in determining whether a body was a passenger or a driver?

Answer 16

1. Seatbelt impression - injury from how the seatbelt runs across the stomach
2. “Dicing injury” - side glass windows are prone to shatter, while windshields are meant to stay together. Obv, if they have a shattered glass injury on left side of face, they are either a passenger or driverside passenger.

Question 17

What are the three main things that come out a gun when fired which are useful in determining firing distance, and how far do they go? What injury do they cause?

Answer 17

1. Bullet - goes far
2. Soot - goes 6-7 inches - no injury, just carbon deposits on skin
3. Gunpower - goes up to 36 inches - stippling injury

Question 18

When will a contact range firearm injury result in a stellate-shaped wound vs not?

Answer 18

In the head where there is no room for the gas to expand -> stellate-shaped tearing

In the other body cavities like abdomen -> no stellate wound since they can dissipate in the body

Question 19

What is characteristic on the skin of contact range shots?

Answer 19

Searing of the skin edges and muzzle imprint

Question 20

What is considered “near-contact” range and what will be found there?

Answer 20

2-3 inches. Soot and gunpowder stippling over low distribution, with muzzle flame possibly burning skin edges

Question 21

What is considered close vs intermediate vs distant range and the injuries there?

Answer 21

Close - Within 8 inches, soot may still be present
Intermediate - Up to 36 inches, stippling will still be present
Distant range - Only characteristic is entrance wound, no stippling. Impossible to determine exact distance

Question 22

At what range will shotgun pellets start to fan out?

Answer 22

About 4 feet, before that it is a tight circle

Question 23

Why is clothing important to keep in a gunshot victim?

Answer 23

May have soot / gunpowder on it which indicates the entrance wound

Question 24

What will typically be present on an entrance wound but not an exit wound?

Answer 24

1. bevelling of bone on the inside

2. abrasion from rubbing the edges of the bullet through the skin

Question 25

When will an abrasion rim be present on an exit wound?

Answer 25

When there is external pressure against the area of exit (i.e. collar, floor, wall on opposite side)

Question 26

How are cuts different than stab wounds?

Answer 26

Cuts = incised wounds - superficial and longer than they are deep, from dragging body of blade over skin

Stab wounds - deeper than they are long, from penetration

Question 27

What is the best way to determine the dimensions of the blade used?

Answer 27

Bring the skin together and measure the blunt spine of the blade (stab wound only)

Question 28

What is required for asphyxiation?

Answer 28

Lack of oxygen to tissues -> typically cerebral anoxia, cause of death in hanging

Question 29

What is typical in the conjuctiva of the eyes in strangulation, as well as neck muscles?

Answer 29

Conjunctiva - petechial hemorrhages

Neck muscles - hemorrhage into the strap muscles

Question 30

What structures remain intact in ligature / manual strangulations in young people but not older people?

Answer 30

Hyoid bone and thyroid cartilage

Question 31

How can you commit suicide by smothering? What is the number one risk factor for smothering children?

Answer 31

Suicide - putting bag over your head

In children - cosleeping with obese parent

Question 32

What is traumatic asphyxia vs positional asphyxia?

Answer 32

Traumatic - i.e. being crushed by something which compromises your breathing, like an automobile after a collision

Positional - i.e. lying on your face when passed out from alcohol poisoning

Question 33

What is drowning vs near drowning?

Answer 33

Drowning - death occurs while in water or within 24 hours of removal from water

Near drowning - death from complications arising from being submerged in water, greater than 24 hours after the incident

Question 34

What autopsy findings / lab tests diagnose drowning?

Answer 34

None! Need to know the circumstances around the death to rule an accident vs suicide/homicide

Question 35

What will be the appearance of the skin due to carbon monoxide poisoning? What amount is typically the critical level?

Answer 35

Skin - cherry-red lividity (pink), can also be due to cyanide or hypothermia

15-20% CO in those with COPD may be lethal, although 50% is generally lethal

Smokers can have 8-10% just normally

Question 36

What will happen to the muscles of a burnt body?

Answer 36

Pugilistic appearance - contraction of arms and legs, with heat-related fractures common, including skull

Question 37

How can you tell a artifactual vs real injury hematoma in a burn patient?

Answer 37

Artifactual - epidural hematoma (blood within bone mmarrow extrudes into epidural space due to heat)

Real - subdural hemotoma, due to bleeding in skull, a real injury

Question 38

What two indicators are good at determining whether the decedent was alive at the time of the fire?

Answer 38

1. Carboxyhemoglobin level - must’ve been breathing it in

2. Soot in the lungs due to inhalation

Question 39

How do you estimate the burn coverage of a body?

Answer 39

Rule of 9's
Chest + abdomen - 18%
Back and buttocks - 18%
Front or back of each leg - 9%
Front or back of each arm - 4.5%
Front or back of head - 4.5%

Question 40

What is the greatest determinant of electrical resistance in the human?

Answer 40

Skin - determines the amperage depending on low / high voltage

Question 41

What are the low vs high voltage mechanisms of death? Which is associated with a burn?

Answer 41

Low voltage - ventricular fibrillation due to current in heart

High voltage - Thermal injury from current, or respiratory arrest due to brainstem damage
-> only high voltage associated with burn

Question 42

How is diagnosis of heroin overdose made?

Answer 42

6 monoacetylmorphine in blood -> specific metabolite for diacetylmorphine (heroin does not persist in blood)

Question 43

How is diagnosis of cocaine overdose made?

Answer 43

Cocaine in blood, or benzoylecgonine in blood due to 4-5 hour halflife (can still break down after death without liver function due to plasma esterases)

Question 44

What is the cause of death in cocaine vs heroin overdose?

Answer 44

Cocaine - cardiac arrhythmias and strokes

Heroin - respiratory depression, often with drowning if people try to put them in water to resuscitate

Question 45

Why are children’s brains more susceptible to rotational forces? Do these forces commonly cause head injury?

Answer 45

They are large (vs adult brain proportions), have higher water content, are soft, and have a flat, short, and narrow skull base allowing for increased movement. Often, fontanelles are not yet closed.

Yes-> translational forces are infrequently the cause of diffuse brain injury in children

Question 46

What is a very common finding of rotational brain injuries in young children?

Answer 46

Retinal hemorrhages -> especially in non-accidental trauma, but still can be seen in accidents

Question 47

What is the general cause of epidural vs subdural hematoma? Why are adults more likely to get both?

Answer 47

Epidural - temporal bone fracture with tear of middle meningeal artery (typical of children less likely due to firm adherence of dura to skull in children, vs adults its loser)

Subdural - venous bleeding due to tearing of a bridging vein, most often due to tension of bridging veins in brain atrophy (alcoholics and older adults)