Heat-related deaths: forensic diagnosis, death certification and reconciliation with excess-mortality estimates

Extreme heat produces a substantial mortality burden that is captured through two incompletely connected systems: individual medicolegal investigation and population-level statistical attribution. This review defines the distinct causal constructs measured by these systems and proposes a practical framework for integrating forensic diagnosis, death certification, and excess-mortality surveillance.

A structured narrative review of the published literature was conducted from database inception through 17 July 2026. Evidence was integrated across heat-illness pathophysiology, forensic scene investigation, autopsy and ancillary testing, differential diagnosis, death certification and coding, vulnerability, occupational fatalities, and temperature-mortality modelling. Particular emphasis was placed on reconciling individual medicolegal case ascertainment with epidemiological estimates of excess mortality. Reporting was guided by the Scale for the Assessment of Narrative Review Articles (SANRA).

Fatal environmental hyperthermia is usually an exclusionary diagnosis because gross and microscopic findings are nonspecific and may be modified by cooling, survival interval, postmortem interval and decomposition. No biochemical, immunohistochemical, proteomic, or lipidomic marker independently confirms the diagnosis. Heat may be the principal cause of death, a material contributor acting through natural disease, or a population-attributable exposure that cannot be assigned confidently to an individual decedent. Certification practices vary across jurisdictions, and matched event comparisons show that modelled excess mortality can exceed individually attributed deaths without making the two measures interchangeable.

Forensic and epidemiological counts should be reported as complementary measures. Standardized scene data, case-appropriate toxicology, explicit certification of contributory heat exposure, linkage of medicolegal and vital-statistics records, and joint interpretation with excess-mortality models would improve surveillance and prevention.