Pathology

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

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

Petechia Very small hemorrhages

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.

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.

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)

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

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

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

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

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

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.

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

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

Normal Postmortem Changes Rigor mortis Livor mortis Desiccation Putrefaction Autolysis

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

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

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)

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)