Death investigation and identification
A defensible death investigation connects the scene, medical history, external and internal examination, laboratory results and the circumstances under which each observation was obtained. Distinguish an underlying disease or injury from the final physiological mechanism. Cardiac arrest describes an event common to deaths and does not explain what initiated the fatal sequence. A causal sequence should be medically coherent and should acknowledge unresolved alternatives rather than substitute a vague mechanism for missing information.
Postmortem changes are contextual evidence, not a collection of exact clocks. Cooling depends on environment, body size, clothing, contact surfaces and preceding temperature. Lividity reflects dependent blood distribution and can provide information about position, but fixation and color vary. Rigor involves biochemical changes in muscle and has substantial variability. Decomposition, adipocere and mummification reflect interacting environmental and intrinsic conditions. No isolated color or textbook interval establishes an exact time of death in every body.
Laboratory estimates also have assumptions. Vitreous measurements may be less vulnerable than blood to selected postmortem changes, but they are not unchanged replicas of a living person's chemistry. Potassium rises and decomposition can limit interpretation. A validated estimation method requires appropriate sampling, a suitable reference model and an uncertainty interval. Gastric contents alone cannot reconstruct a precise last-meal time or prove an account of the circumstances.
Identification uses comparability and the strength of the evidence. Fingerprints, dental comparisons, medical devices and DNA can contribute when suitable antemortem information is available. A DNA match statistic concerns a defined proposition and population, not the probability that an individual committed a crime. Mitochondrial DNA can be valuable in degraded material because of its high copy number, but shared maternal lineages limit individual discrimination. Low-template results require attention to contamination and stochastic effects.
Skeletal and dental assessments provide estimates with population and method limitations. Sex estimation, developmental age and stature are not direct observations of identity or legal status. Do not turn broad morphological associations into certainty about ancestry or a precise birth date. An unexplained sudden death in a young person can require focused histology, toxicology and appropriate genetic or family evaluation. A negative gross examination does not demonstrate that no lethal physiological process occurred.