Cocaine did not simply decline between early postmortem sampling and autopsy. Hearn and colleagues reported different directions of change across blood collection sites, including increases in some femoral samples and decreases in most of the small subclavian subset. Neither a universal degradation correction nor a universal redistribution multiplier described these observations.
Early sampling was still postmortem sampling
The investigators selected medical examiner cases in which circumstances suggested cocaine use. Blood obtained during the initial investigation was compared with later autopsy specimens. “Scene” blood was not a controlled sample collected during life; some intervals were measured from discovery because the time of death was unknown.
The report presents seven detailed cases and overlapping site-specific subsets: six heart comparisons, six femoral comparisons and four subclavian comparisons. These should not be added together as 16 independent deaths or described as seven observations for every site. Not every case had the same specimens.
Scene specimens were collected in tubes containing sodium fluoride and potassium oxalate and refrigerated for transport. Autopsy specimens received the same preservatives and were refrigerated after the examination. These measures addressed handling after collection; they could not prevent changes that had already occurred within the body.
What did the paired site results show?
In the six heart comparisons, three autopsy concentrations were approximately 33–275% higher; the other three remained essentially unchanged. Scene-to-autopsy intervals were approximately 5–20 hours. In the six femoral comparisons, five rose approximately 22.5–117%, while the lowest initial result decreased from 0.10 to 0.06 mg/L over 21 hours.
In three of four subclavian comparisons, concentrations were approximately 15–48% lower at autopsy after 7–20 hours. The fourth increased from 3.0 to 5.0 mg/L after five hours. These were descriptive small-subset observations, not a statistically validated predictor for a new death. Time alone did not consistently explain the direction or size of change.
One case illustrated the opposing patterns particularly clearly: subclavian cocaine decreased from 2.3 to 1.2 mg/L, while femoral cocaine increased from 1.8 to 3.9 mg/L over a reported 20-hour sampling interval. Choosing only one of those trajectories would misrepresent the case.
Aorta comparisons combined site and time
Five comparisons placed later aorta blood against earlier blood from another site. Later values were higher, but these were not paired aorta collections. They could not isolate a change over time from a difference between vessels. The paper also contains a collection-label inconsistency in its first case: prose describes the later peripheral specimen as femoral, while the table labels it iliac.
The authors considered release from tissue stores and hydrolysis competing explanations. They also acknowledged possible initial site differences and the possibility that a second femoral collection drew blood that had moved from more central vessels. The study did not directly quantify each mechanism’s contribution.
What analytical evidence supported the comparison?
Screening and preliminary identification used several techniques. Cocaine and benzoylecgonine quantitation used GC–MS with deuterated internal standards. Samples from each case were analyzed in the same batch and results were means of duplicate measurements.
The paper reported a linear range of 0.02–10.0 mg/L, with coefficients of variation of 6.9% for cocaine and 7.2% for benzoylecgonine. It did not provide a modern, complete validation dataset establishing a separate uncertainty for every specimen. In one case the small benzoylecgonine differences were explicitly discussed against method variation, rather than automatically interpreted as biological change.
What can the study establish in case review?
A collection site’s reputation as “peripheral” does not guarantee that a later concentration remained unchanged. Conversely, a stable pair does not prove that no competing processes occurred. Exact vessel, collection technique, preservation, timing and the distinction between death and discovery need to accompany a reported result.
The study does not reconstruct an individual’s premortem concentration, impairment or cause of death from an autopsy number alone. Compare the separate problem of unmatched cocaine group averages and the broader evidence from sequential postmortem sampling.
Primary source
Hearn WL, Keran EE, Wei H, Hime G. Site-Dependent Postmortem Changes in Blood Cocaine Concentrations. Journal of Forensic Sciences. 1991;36(3):673–684. doi:10.1520/JFS13076J.
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