Forensic Pathology: Asphyxia and Drowning Investigations

Forensic Aspects of Asphyxia

Carotid Artery Occlusion

Loss of consciousness typically occurs within 10-15 seconds of complete occlusion of the carotid arteries. This timeframe allows for the implementation of restraint mechanisms.

Differential Diagnosis at the Scene

Differential diagnosis is crucial and is made at the scene, considering:

• The victim's clothing state.
• Presence of extracervical lesions indicative of control or struggle.
• Severity of neck injuries.

The diagnosis of accidental etiology is based on a meticulous examination of the scene. A high blood alcohol level may explain the victim's low resistance or the possibility of accidental strangulation.

Forensic Pathology of Submersion (Drowning)

Definition and Types of Submersion

Death or pathological disorder caused by the introduction of a liquid (usually water) into the respiratory tract. Death immediately following submersion is considered "primary". Pathological liquid penetration, which can eventually cause death subsequent to submersion, is considered "secondary".

Submersion can be classified by the body surface covered and the nature of the liquid:

• Complete Submersion: The entire body is immersed in water.
• Incomplete Submersion: Only the breathing orifices are covered by water.

Depending on the type of water, submersion can occur in fresh water or salt water.

Pathological Findings in Submersion

External Examination

Key external alterations include:

• Cadaveric Lividity: Often much clearer, and the body's hue generally remains distinct due to ambient temperatures lower than the submersion environment.
• Cutis Anserina: Victims frequently exhibit the phenomenon of cutis anserina (goosebumps), a contracture of the arrector pili muscles, which is a striking finding during external cadaveric examination.
• Maceration: Characterized by wrinkling and whitening of the skin of the hands and feet, which can progress to epidermal detachment. These are important diagnostic findings, indicating a vital reaction.
• Cadaveric Spasm, Foam, and "Drowning Fungus": A frothy exudate may emerge through the nostrils and mouth.

Internal Examination

Injuries, often blunt force trauma, may be present, though most cases are post-mortem findings.

Respiratory System

• The most characteristic finding is tracheobronchial foam.
• Foreign bodies (e.g., sand, grass) may also be present.
• The lungs are enlarged and may show impressions (fovea) from external pressure.
• Paltauf spots (petechial hemorrhages) may be observed.
• Palpation of the lungs often reveals a characteristic crepitus.
• The lungs appear very congested ("wet lungs").

Other Organs

• Stomach: Water, sometimes exceeding 500 ml, indicates intravital liquid penetration during immersion. The duodenum may also contain water.
• Spleen: There may be a reduction in spleen weight and the splenohepatic weight ratio.
• Middle Ear and Mastoid Cells: Hemorrhage may be found.

General signs of asphyxia, such as petechial bruising (external and internal), are not always abundant, and blood fluidity is often increased.

Complementary Examinations

Radiologic Examination

Radiologic examination may reveal opacity of the sinuses, indicating vital submersion.

Microscopic Examinations

These examinations focus on lung histopathology and the detection of submersion biomarkers.

• Histology: Lung tissue may show a pseudo-emphysematous image, with thinning and rupture of interalveolar septa, and foci of intra-alveolar edema. Foreign bodies may indicate a vital reaction.
• Biomarkers: Key biomarkers of submersion include ciliated protozoa and, especially, diatoms.

For diatoms to be considered evidence of death by drowning, certain conditions apply:

1. The risk of contamination during the analytical process must be minimized. Glassware must be scrupulously clean, and reagents of high purity.
2. All diatoms that may have been present in the body during life must be identified and excluded from consideration as evidence of drowning.