1. Pathology

2. Strangulation
Strangulation implies pressure to the neck. Deaths due to strangulation are forensically important.
It can be defined as a circumferential squeezing of the neck that is independent of the gravitational weight.
Manual strangulation
Ligature strangulation
Choke holds

3. Signs of Strangulation
Obstruction of veins with impaired blood return to the heart, leading to cyanosis (a blue color), tissue swelling, and petechia (very small hemorrhages).
Obstruction of arteries
Stimulation of pressure receptors
Elevation of the larynx and tongue

4. Petechia
Very small hemorrhages

5. Manual Strangulation
Usually caused by men against women. Rarely against another man since a large disparity in physical strength between the assailant and victim is needed.

6. Signs of Manual Strangulation
Disc-like finger-tip bruises
Abrasions
Linear finger-nail scratches (from victim or assailant)
Often limited signs of suffocation as fingers are more likely to probe deeper neck structures and cause reflex cardiac arrest.

7. Signs of Manual Strangulation cont…
Sustained pressure may cause tissue swelling and cyanosis (blueness) of the tongue, pharynx and larynx
Hemorrhage under the skin of the neck
Damage to the larynx (Voice Box)

8. Ligature Strangulation
Where a constricting band is tightened around the neck, there is usually a lot of tissue swelling, and petechia in the face if the pressure is maintained for more than about 20 seconds
The ligature mark is a vital part of the evidence, as it often reproduces the pattern and dimensions of the ligature itself

9. Ligature Strangulation
If the assailant has removed the ligature from the scene, and is then arrested, possible ligatures found on the assailant or in his/her home can be compared with the mark on victim’s neck. (computer imaging is being developed to aid in this field)
Victims may struggle less than manual strangulation

10. Choke Holds
There is often little or no external neck injury visible, while hemorrhages in the muscles can be extensive

11. Asphyxia
Smothering the covering of the mouth or nose (ex: by a plastic bag)
Gagging- the tongue is pushed backwards and upwards, and the gag becomes saturated with saliva and mucus causing further obstruction
Swelling of the airway lining

12. Carbon Monoxide
Carbon monoxide poisoning is a form of asphyxia that results when CO is inhaled
Poorly ventilated houses with faulty heater, house fire, and motor vehicle exhaust are the more common sources
Even small amounts of CO are dangerous, because CO binds to hemoglobin 200 more times than oxygen

13. Carbon Monoxide
Drowsiness and headache occur at carboxyhemoglobin concentration between 10 and 20%
Levels from 20 to 30% can be fatal to persons with pre-existing cardiac or respiratory disease
Levels above 30 to 40% can be fatal to anyone.

14. Note the bright “cherry red” or bright pink color to the hand

15. Drowning Drowning may not produce extensive findings
In some cases, some of the plant material in the water is inhaled
A fluid can be seen coming out from the mouth and nose
Prolonged immersion may produce skin wrinkling
Decomposition is some times delayed by a phenomenon known as saponification: process where some soft tissues make soap

16. Normal Postmortem Changes
Rigor mortis
Livor mortis
Desiccation
Putrefaction
Autolysis

17. Rigor Mortis Stiffening of muscles seconds or minutes after death
Rigor mortis results when ATP concentrations fall
ATP=relaxed muscles
No ATP= contracted muscles
Stops when muscles begin to decompose (~36 hours)
It is used to estimate time of death

18. Livor Mortis
Livor mortis- purplish discoloration of the body and organ surfaces
Becomes visible 30 minutes to 2 hours after death
Results from breakdown of hemoglobin (leaks in tissues)
Also used to estimate time of death

20. Other Normal Postmortem Changes
Desiccation- mucous membranes (lips, eyes) shrivel and look darkly colored
time depends on location of the body, environmental conditions
Putrefaction-
Greenish discoloration of skin
Growth of bacteria unchecked by immune system causes gas production which may swell, rupture organs or make soft tissue appear swollen
Time again depends on environment of body (few days to weeks if colder)

21. Normal Postmortem Changes
Autolysis- cells begin to break open and ooze contents
Soft tissues start to become a liquid
Proteins break down and then are degraded by bacteria (this is what causes the smell)