Asphyxial and environmental deaths
Asphyxial investigation requires a coherent mechanism rather than one supposedly diagnostic external sign. Petechiae and facial congestion can occur in several circumstances and are not specific proof of strangulation. A ligature pattern may suggest the direction of loading, but the scene and internal examination remain essential. Partial suspension can be fatal, so contact of the feet or knees with a surface does not exclude a hanging mechanism. It does not follow that every suspended body died from suspension or that the manner can be assigned from a mark alone.
Drowning concerns respiratory impairment from immersion or submersion. Hypoxia and lung injury are central to clinical deterioration in both fresh and salt water; older accounts that make massive systemic electrolyte shifts the universal primary mechanism are misleading. Froth, edematous lungs and aspirated material can support a coherent investigation but are not individually diagnostic. The absence of froth does not rule out drowning, and finding a body in water does not prove that drowning caused death.
Diatom analysis has important contamination, sensitivity and interpretive limitations. Matching environmental material and appropriate controls can improve an investigation, but a positive result is not an automatic demonstration of where or how a person died. The same caution applies to changes caused by immersion, decomposition, resuscitation and handling. Clearly distinguish a possible explanation from a conclusion established to the applicable evidential standard.
Fire investigation integrates scene circumstances, burn distribution, airway findings and relevant toxicology. Soot in distal airways and a substantial carboxyhemoglobin level can support breathing during smoke exposure. A low level does not by itself prove postmortem burning, because rapid death and different exposure conditions can alter the pattern. Heat can produce a flexed posture without a living defensive response. Burn appearance alone does not establish whether death was accidental or inflicted.
Electrical and temperature-related deaths can leave subtle or nonspecific findings. A contact mark or characteristic lightning-associated pattern can support a relevant exposure, while the absence of a conspicuous burn does not exclude dangerous electrical injury. Hypothermia findings require context and differential assessment, and heat illness can involve multiple organs. Avoid rigid assertions that one voltage class always causes one terminal mechanism. Occupational safety, specimen handling and scene precautions are part of a defensible examination, not optional additions after an interesting diagnosis is proposed.