Abstract Cells depend on a continuous supply of oxygen to produce energy. Any severe disturbance in ventilation, gas exchange, oxygen transport, or tissue perfusion may lead to hypoxia and subsequent dysfunction of sensitive organs, especially the brain and heart. In forensic science, understanding this sequence is important when examining cases of mechanical asphyxia, low-oxygen environments, and some forms of poisoning. Simplified Physiological Pathway of Oxygen Delivery Air/O₂ → Lungs → Blood → Heart → Brain and tissues. Airway obstruction, compression, toxic exposure, or low-oxygen environments can interrupt this chain. Forensic assessment therefore requires the integration of scene information, autopsy findings, and laboratory results. Physiological Basis Oxygen enters the lungs, diffuses across the alveolar-capillary barrier, binds to hemoglobin, and is then transported by the heart and circulation to the tissues. When oxygen delivery decreases, cells rely increasingly on anaerobic metabolism, ATP production falls, and membrane and ion functions become disturbed. The brain is highly sensitive to oxygen deprivation; therefore, loss of consciousness may occur rapidly in severe cases. Connection to Forensic Evidence No single anatomical finding is sufficient by itself to prove mechanical asphyxia. The forensic pathologist therefore integrates the circumstances of the scene, examination of the neck and chest, external and internal injuries, histological findings, and toxicological testing. Some traditional signs may be absent in certain cases, making an integrated assessment essential. Educational Applied Example In a death where pressure on the neck is suspected, the presence or absence of petechial hemorrhages alone is not enough to reach a conclusion. The mechanism of oxygen deprivation, deep neck tissue injuries, autopsy and toxicology findings, and information from the scene should all be evaluated before a final interpretation is made. Key Learning Points • Oxygenation is a sequential process that begins with ventilation and ends with oxygen reaching the cell. • Hypoxia can rapidly impair organs with high energy requirements. • Forensic diagnosis of asphyxia depends on a combination of evidence rather than a single sign. Conclusion This topic demonstrates that physiological knowledge is not merely theoretical; it helps interpret biological evidence within a forensic context. Professional conclusions, however, should be based on the integration of clinical or autopsy examination, scene findings, and laboratory testing rather than on a single isolated sign. Selected References 1. Fatal mechanical asphyxia: a comprehensive forensic review with an illustrative case. 2025. PubMed PMID: 41032957. 2. Research Progress on Molecular Changes in Pulmonary Hypoxia and Cause of Death Identification in Mechanical Asphyxia. 2023. PubMed PMID: 37038857