Antemortem and Postmortem Cannabinoid Samples Used Different Preservatives
The available antemortem and postmortem blood samples differed in preservative as well as collection time and physiological state. A concentration difference could not be isolated as a pure effect of death or redistribution.
The paired subset was small
Only three cases in the human series had available antemortem whole blood. Hospital specimens were preserved with potassium EDTA, whereas central and peripheral postmortem specimens were collected into sodium-fluoride tubes. The postmortem sampling sites were cardiac and iliac-vein blood.
Several processes separated the measurements
Time before death, continued metabolism before death, anatomical sampling and postcollection stability could contribute to a comparison. Different preservatives add another qualification. The study did not hold all those factors constant or provide a formula separating their individual effects. Similar concentrations likewise would not demonstrate that no changes occurred.
Use the evidence as a bounded comparison
The small paired subset is valuable because it provides observations across the death interval. It does not establish a universal postmortem correction factor or allow reconstruction of a concentration at an earlier crash. A defensible account keeps each sample’s collection time, site, tube and handling history attached, then treats impairment and causation of death as separate questions requiring additional evidence.
Related analysis: the limits of central-to-peripheral ratios.
Research cited
Holland and colleagues (2011). Postmortem redistribution of THC, 11-hydroxy-THC, and THCCOOH. DOI: 10.1016/j.forsciint.2011.06.028.
