Forensic Medicine 2 Flashcards
What are the traditional signs of asphyxia?
1) Facial congestion
2) Facial oedema
3) Cyanosis of the skin
4) Petechial haemorrhages
What is facial congestion?
It is a traditional sign of asphyxia. Happens due to venous drainage caused by damage and resulting in obstructed venous return to the heart
What is facial oedema?
It is a traditional sigh of asphyxia. Happens due to raised venous pressure causing plasma leakage from the blood vessels into the soft tissue of the face
What is Cyanosis of the skin?
A traditional sign of asphyxia. This is a blue discolouration of the skin as a result of the failure of oxygenation of the blood. If a person is centrally cyanotic then they will have a blue discolouration to their face and hands.
What are petechial haemorrhages
A traditional sign of asphyxia. Can be seen in the conjuctival membrane and the loose skin of the head and neck. Appears as tiny pin prick haemorrhage caused by elevated venous pressure
What are the pitfalls of trying to identify death by asphyxia using the traditional signs?
1) the signs are not specific to asphyxia and may occur in other circumstances such as natural deaths
2) classic asphyxial signs may be pronounced in a traumatic asphyxia such as a murder
3) Where death occurs rapidly as a result of irrespirable gas there may be no evidence of the traditional signs of asphyxia
In what circumstances might a death due to the absence or low content of oxygen in respire air occur?
1) industrial or agricultural accidents
2) rust in a ship’s hold or grain in silos can remove atmospheric oxygen
3) CO2 can accumulate in deep chalk wells
Talk about plastic bag asphyxia
This is common in suicides or accidental deaths of young children. Congestive features and petechial haemorrhages are virtually always absent because there is no venous obstruction. Death can be very rapid
What is smothering?
Smothering is the deliberate occlusion of the mouth and nose by hands, clothes, bedding etc. It is often a method of homicide in the elderly or those with limited capacity to fend off their attacker. Accidental smothering is possible usually as a result of epilepsy or severe intoxication.
What are the common indications that a person has been smothered?
Smothering seldom produces the traditional signs of asphyxia unless there has been a violent or prolonged struggle. It may be difficult to diagnose at autopsy and careful assessment of the oral-facial tissues is a must.
What are the potential problems with identifying a smothering death?
Haemorrhagic lividity may cause serious interpretive difficulty in a body lying face down or where apersons head is hanging off the side of a bed. Per-orpital hypostatic pressure pallor may also lead the inexperienced to a diagnosis of smothering
What is choking?
This term is usually applied to an internal obstruction of the upper air passages and is commonly caused by an object or substance impacted within the pharynx or larynx. This obstruction may produce serious respiritory impairment with distress, cyonosis or in some cases, rapid cardiac arrest. Typically accidental.
What is aspiration?
inhaling food particles into the lungs which can lead to a person developing aspirational pneumonia. Choking is aspiration with bigger pieces
When does aspiration commonly occur?
1) When a person is intoxicated
2) As a result of the depression of the central nervous system as an effect of anaesthetic which dampens reflexes. This is mitigated against by having a person not eat or drink anything before a surgical procedure. In emergencies surgery will take place regardless of what the person has eaten and additional precautions such as crichord pressure will be taken
What are the potential pitfalls of diagnosing choking by food material?
It is important to remember that finding some food in the air passages is not diagnostic of death by choking as it may have been transferred post-mortem as an artefact as when you die muscles relax and the protective mechanisms that normally stop the reflux of food may stop working.
What are the consequences of neck pressure?
1) obstruction of the jugular vein causing cyonosis, oedema and/or petechial haemorrhages
2) Obstruction of the carotid arteries which may cause cerebral ischemia (decreased oxygen to the brain due to ipaired blood supply)
3) stimulation of the barorecpeter nerve endings in the carotid sinus and sheaths
4) elevation of the larynx and tongue, closing the ariway at the level of the pharynx
What is reflex cardiac arrest?
in theory it is excessive sensory stimulation precipitating reflex cardiac arrest. It is more likely when a person is in a highly emotional state or under the influence of alcohol or drugs. Can have medico-legal consequences.
Give example of things that may trigger reflex cardiac arrest…
dilation of the cervix during a criminal abortion, cold water or food impacting the larynx, trauma to the testes, sudden immersion in icy water or sudden pressure to the neck
How does reflex cardiac arrest happen in cases of pressure to the neck?
1) stimulation of the carotid sinuses and adjacent baroreceptors
2) impulse ascends through the glossopharyngeal nerves in the brain stem
3) impulse descends through the vagus nerve to the heart
4) profound slowing of the heart rate and or cardiac arrest
What is manual strangulation?
It involves neck pressure or sleeper holds. It is easier to successfully strangle someone who you are stronger than and hence it is much more common for men to strangle woman and children than vice versa. Can be performed using one or both hands from the front or behind the victim
What are the signs of manual strangulation?
1) externally the typical features are bruising and abrasions of the skin of the neck and the jaw. The bruises may be discoid from fingertip pressure but larger areas may be seen. Scratches from linear abrasions caused by fingernails being scraped along the skin’s surface may also be observed- these may be from either the killer or victim.
2) Internal findings may include areas of haemorrhage in the strap muscles at the front of the neck, possible haemorrhages behind the oesophagus and trachea and to the front of the cervical spinal column. May also get damage or fractures to the larynx and hyoid, this is more likely in older people who’s larynx’s may have become ossofied/calcified.
What is ligature strangulation?
Ligature strangulation occurs where a constricting band is applied to the neck. There may be classical asphyxia signs. The lif=gature mark may be an important piece of evidence as it may replicate a patterned aspect of the ligature itself and thus offer a clue as to what was used. The appearance of the mar will depend on what was used and how long it was applied.
What is hanging?
Hanging is a form of ligature syangulation where the pressure is produced by the bodies own weight
Partial v Full suspension
a person hanging from a ceiling would likely be fully suspended whereas a person who is partially suspended may be kneeling or even sitting
High v low suspension point
high suspension points are usually ceilings or beams and are more common than low suspension points such as bed rails or door handles. Low suspension point hangings are most often seen in prisons
What are the most common post mortem findings in hangings?
external findings will vary based on the particular circumstances but usually produces a rising ligature arc on the neck, frequently with a suspension peak or gap in the mark where the body weight has pulled the ligature away from the skin.
Asphyxial changes may be absent and a fracture of the cervical spine is extremely rare in suicidal hangings
Sexual asphyxia
Death is almost always accidental. In theory sexual gratification is heightened by neck pressure inducing cerebral hypoxia. Self suspension or partial strangulation is the most frequent manifestation of this activity. Frequently other findings at the scene of the death to suggest a sexual element to the death.
What is traumatic asphyxia?
May occur in a variety of circumstances and is well recognised in mass fatality incidents or in idividuals trapped in sand/grain or underneath vehicles
What are the signs of traumatic asphyxia?
Fixture of the chest such that respiratory movements are impaired causing an increase in intra-thorastic pressure which interferes with blood return to the heart.
Pronounced congestion and cyanosis of the head and neck, and usually descending to the thoracic inlet. There may also be florid petechial haemorrhages and it is also common for blood to emerge from the nose.
Internally there may also be damage to the thorax
What is postural asphyxia?
Often seen in the context of drunk or otherwise intoxicated people falling into a confined space and thereby impairing their own chest expansion and respiration from which they cannot escape.
What is positional asphyxia?
This is a concern in deaths in police custody where a suspect has been forcefully restrained on the ground with the arresting officer’s knees on their back. This is especially dangerous when the victim is obese or intoxicated, or there are multiple arresting officers.
What are the safe limits of alcohol consumption?
Around 21 units per week for men and 14 units per week for woman
Where does the majority of absorption of alcohol take place?
The stomach, duodenum and jejunum. Additionally, the small intestine absorbs the nutrients in food and alcohol
