Toxicology laboratories may be funded by a variety of government (i.e., federal, state, county, city, regional, etc.) or private entities. The variability in funding has led to differences in staffing, equipment, testing, and reporting capabilities within the organizations conducting analysis in impaired driving cases. The lack of standardization coupled with stop-testing practices has led to incomplete data on drug-impaired driving. The insufficient data can impact our national and local traffic safety partners in various ways, including substance abuse treatment, driver education on impairing substances, and the development of appropriate countermeasures.
As a primer to assist in understanding the terms that forensic toxicologists and our traffic safety partners may use in their reports, supporting documentation, research, and courtroom testimony, consider the following:
- Forensic Toxicology: Application of toxicology for the law
- Human Performance Toxicological Testing: Analysis of specimens for driving while impaired cases, drug-facilitated crimes, and other impairment cases to determine the presence (or absence) of chemical substances and their effects on the average individual
- Biological Specimen/Matrix: Specific biological fluid or tissue (e.g., blood, plasma, serum, urine, vitreous fluid, hair, and tissue) to be tested
- Court-ordered Toxicological Testing: Analysis of specimens from subjects involved in probation and parole, drug courts, or child protective services to determine the presence (or absence) of chemical substances and their effects on the average individual
- Analyte (Drug/Chemical Substance): Chemical substance to be identified and/or measured
- Analytical Scope: Selection of drugs, drug metabolites, and other chemicals covered in an analytical testing scheme
- Pharmacokinetics: The study of how the body interacts with drugs, including alcohol, and includes the movement of the drug into (absorption), through (distribution and metabolism), and out (elimination) of the body
- Pharmacodynamics: The study of how drugs affect the human body and their mechanisms of action
- Identification: Assignment to the most specific drug class attainable
- Interpretation: Explanations for the observations, data, and calculations
- Opinion: View, judgment, or belief that takes into consideration other information in addition to observations, data, calculations, and interpretations
- Qualitative method: Assay designed to determine the presence of an analyte within a sample relative to an established threshold
- Quantitative method: Assay designed to measure the concentration of an analyte within a sample
- Stop Testing: If the concentration of alcohol in a biological sample is above a set threshold (i.e., 0.08 g/dL), no further toxicological testing is conducted
Understanding the role alcohol and other drugs may play in impairment cases involves comprehensive toxicological testing, appropriate interpretation, and collaboration with traffic safety partners. How comprehensive each of these facets reaches will contribute to the ability to effectively and appropriately communicate this information, assist our traffic safety partners in appropriate countermeasures, and effectively combat the public health threat posed by impaired driving.
Unlike alcohol, the ability to correlate the concentration of any drug or its metabolite(s) to a specific level of impairment is not possible. Therefore, through the standards development process, the scientific community has provided guidance to forensic toxicologists and users of their data on what is scientifically appropriate to address in expert opinions and testimony. Per the ANSI/ASB Best Practices Recommendation 037 “Guidelines for Opinions and Testimony,” when asked to provide an opinion on the toxicological findings, a toxicologist:
- may discuss the toxicological impact of the presence, absence, and/or stability of drugs or other chemicals
- may address impairment for the average individual to the extent that effects are consistent with documented pharmacodynamic and toxicodynamic properties of the substance and within the context of a given case
- should not address behavioral intent based solely upon a drug concentration
- should not opine as to a specific individual’s degree of impairment based solely on a quantitative result
- should not imply impairment of an individual based on analytical findings from urine, hair, or other matrices unless supported by the literature
- should not perform extrapolation calculations for drugs other than ethanol
Toxicological testing and testimony on the data that toxicologists generate stand as essential elements in the impairment investigation. Equally important, the data must accurately identify all drugs found in a motorist suspected of impaired driving. Further, when challenges related to data collection exist in toxicology laboratories, the information should be communicated to our traffic safety partners. Imperative to the integrity of the process lies in open lines of communication between all traffic safety partners and that we remain engaged in continuous interactions.
This article serves as an initial primer on forensic toxicology, the challenges that toxicologists and government-funded laboratories face, and the obstacles preventing many of our labs from providing comprehensive data and represents the first in a series of articles designed to provide judges, court staff and practitioners with greater understanding of the interplay between forensic toxicology and impaired driving cases.
Learn more about the Regional Toxicology Liaison program.