By Dr. David Lehmann
The Snapshot vs. The Motion Picture
In alcohol and drug-related litigation, numbers take center stage. A blood concentration is reported, a timeline is constructed, and a legal conclusion is often drawn. But a laboratory result is just a snapshot in time.
Toxicokinetics is the motion picture. It allows us to assess the timeline of an incident, evaluating how a substance moves through the body over time.
The ADME Framework
Understanding impairment requires consideration of the underlying biological processes. Toxicokinetics focuses on four core stages:
Absorption: How the substance enters the bloodstream (and how fast).
Distribution: How it moves from the blood into tissues and the brain.
Metabolism: How the body chemically breaks the substance down.
Excretion: How the substance finally leaves the system.
Why It Matters in the Courtroom
Toxicokinetics isn’t an academic abstraction; it provides a scientific framework for informing interpretations of a person’s condition at a specific moment in time. It allows us to address the “physiologic realities” of a case:
Calculating BAC at different times: It provides the mathematical and biological framework used to estimate what a concentration would have been at the time of driving (i.e., retrograde extrapolation).
Timing: Was the concentration rising or falling at the time of the incident?
Consistency: Is the reported drinking history consistent with the laboratory results?
Interactions: How do multiple substances change the way the body processes each?
The Expert’s Role
Toxicokinetics provides a structured framework for interpreting chemical exposure. A toxicologist’s role is to apply established scientific principles to the available data and to explain what conclusions can—and cannot—be drawn from that information.
When applied appropriately, toxicokinetics allows the analysis to move beyond a single measurement and toward a scientifically grounded evaluation of possible exposure scenarios, while identifying relevant assumptions and sources of uncertainty.
What’s Next?
This post begins a four-part series. In the coming weeks, we will dive deep into each stage of ADME—starting with Absorption—to explore how these biological processes can significantly influence the interpretation of a legal argument.
Disclaimer*: *All views expressed here are my own and do not reflect the views of my employer or any affiliated organizations or partners.
