The Evidence Behind the Number: Why Specimen Collection and Retention Matter in Postmortem Toxicology

The toxicology report tells you what was detected. But before interpreting the result, I want to know something else that matters:

What specimen was tested and when and where was it collected?

In postmortem toxicology, those details can significantly affect how a laboratory result should be interpreted.

A concentration reported on a toxicology report is not simply a number that exists independently of the specimen from which it was measured.

SPECIMEN TYPE MATTERS.

Peripheral blood, central blood, urine, vitreous humor, liver, and other tissues do not provide identical toxicological information.

For example, urine can provide valuable evidence of prior exposure but generally cannot establish a blood concentration or degree of impairment at the time of death.

COLLECTION SITE MATTERS.

A drug concentration measured in peripheral blood may differ from one measured in central blood.

This becomes particularly important when evaluating drugs susceptible to postmortem redistribution.

COLLECTION TIMING MATTERS.

The interval between death, refrigeration, autopsy, and specimen collection can affect the interpretation of certain analytical findings.

That is why documentation of when specimens were actually collected—not simply when the autopsy occurred—can be an important part of an independent toxicology review.

PRESERVATION AND STORAGE MATTER.

The type of collection tube, preservative, storage temperature, specimen handling, and chain of custody may also become relevant depending upon the analyte and the questions being asked.

And finally:

SPECIMEN RETENTION MATTERS.

Once biological specimens are discarded, opportunities for additional testing, confirmation, or independent analysis may be permanently lost.

This can become especially important when the original testing did not include a substance later identified as potentially relevant to the investigation.

When I review a death investigation, I don’t begin and end with the reported drug concentrations.

I evaluate the specimen, collection site, collection timeline, analytical methodology, preservation, medical history, autopsy findings, and circumstances surrounding the death.

Because in forensic toxicology the reliability of an interpretation depends not only on what was detected but also on the evidence behind the number.