Postmortem Central Blood Drug Concentrations in Routine Forensic Toxicology: Evidence from Real-World Casework and Interpretive Implications

Background: Postmortem redistribution (PMR) is a major challenge in forensic toxicology, particularly when drug concentrations are measured in central blood rather than peripheral blood. Although peripheral blood remains the preferred specimen for postmortem interpretation, it is not always available in routine forensic practice. Methods: This retrospective descriptive study evaluated postmortem central blood drug findings from judicial autopsies analyzed at the Forensic Toxicology Laboratory of the University of Catania between 2017 and 2024. Approximately, 700 forensic toxicological investigations were reviewed. Overall, 52 therapeutic drugs were identified, resulting in a final dataset of 313 individual drug findings. For each finding, central blood concentrations were compared with published reference ranges and cautiously classified as normal/therapeutic, high but non-toxic, toxic, or potentially lethal. Results: Most findings were classified as normal/therapeutic (84.3%), while 28 (8.9%) were high but non-toxic, 15 (4.8%) toxic, and 6 (1.9%) potentially lethal. The distribution remained broadly consistent in sensitivity analyses restricted to drugs represented by more than 3, 5, or 8 findings. In cases with toxic or potentially lethal findings and available paired peripheral blood data, observed C/P ratios were moderate, ranging from 1.07 to 2.15. Conclusions: These findings do not indicate that central blood can replace peripheral blood or that PMR can be disregarded. However, they suggest that central blood drug concentrations are not intrinsically uninterpretable and may retain practical forensic value when interpreted cautiously within the broader medico-legal context. Central blood results should not be used in isolation to diagnose poisoning, estimate the ingested dose, or reconstruct exact ante mortem concentrations.