1

Scientific & Technical 

Review Panel Final Report 

for 

2020-S-0003

Guidelines for Performing 

Alcohol Calculations in 

Forensic Toxicology

Organization of Scientific Area Committees (OSAC) for Forensic Science
2

STRP Final Report

2020-S-0003

Guidelines for Performing Alcohol 

Calculations in Forensic Toxicology

Organization of Scientific Area Committees (OSAC) for Forensics Science

March 17, 2021

Disclaimer:

This report was produced by an independent Scientific and Technical Review Panel (STRP). The 

views expressed in the report do not necessarily reflect the views or policies of the U.S. 

Government. Visit the OSAC website for more information on OSAC’s STRP process.

Scientific & Technical Review Panel Members

• Richard Alpert, Richard Alpert Law

• Kent Cattani, Arizona Court of Appeals

• Deborah Davis, University of Nevada, Reno

• Jason Hudson, North Carolina Department of Health and Human Services

• Kori Khan, Iowa State University

• Barry Logan, NMS Labs

• Darcy Richardson, Vermont Forensic Services

• Jeff Salyards, Compass Scientific Consulting LLC
3

Report Summary:

The Scientific and Technical Review Panel (STRP) for “Guidelines for Performing Alcohol 

Calculations in Forensic Toxicology” is an independent panel appointed by the National Institute 

of Standards and Technology (NIST). A STRP is established with a range of experts to consider 

how well a standard meets the needs of the forensic science, law enforcement, and legal 

communities, and to recommend improvements to the standard under review. The STRP 

appreciates the efforts of Jennifer Limoges, Forensic Toxicology Subcommittee Affiliate who

managed the development of this draft standard, while serving as the subcommittee liaison to 

this STRP.

The STRP began its review process with a kickoff meeting on September 11, 2020 and 

concluded with this STRP final report. The panel reviewed the draft standard and prepared 

comments for the OSAC Forensic Toxicology Subcommittee. After a rigorous review process 

and discussion between STRP members and the Forensic Toxicology Subcommittee, the 

subcommittee revised the draft standard in accordance with the panel’s comments. The STRP 

has identified consensus opinions around five areas seen as weaknesses in this standard. 

• First, the pharmacokinetic parameters are treated as ranges that suggest each parameter 

has a rectangular distribution. This implication is not supported by the literature and lacks 

statistical rigor. As a result, reporting can lead to inferences that extreme values have 

similar probabilities to more central ones. 

• Second, the method for determining the volume of distribution (Vd) alludes to an 

“anthropometric approach” in one of the references. This method is not adequately 

described in the standard. Furthermore, the reference discusses and ranks several 

different approaches. 

• Third, the standard could provide more clarity about the treatment of postmortem and 

urine samples. 

• Fourth, the accuracy and precision of the blood/breath alcohol levels is treated as an exact 

number without describing the required test methods to make this assumption. 

• Finally, the term, “uncertainty of measurement,” is used to describe the variability of the 

parameters in the population rather than the actual uncertainty of the measurement. 

Report Components:

The STRP reviewed this draft standard against OSAC’s STRP Instructions for Review which 

include the following content areas: scientific and technical merit, human factors, quality 

assurance, scope and purpose, terminology, method description and reporting results. The details 

below contain a brief description of each reviewed content area and the STRP’s assessment of 

how that content was addressed in the draft OSAC Proposed Standard. 

I. Scientific and Technical Merit: OSAC-approved standards must have strong scientific 

foundations so that the methods practitioners employ are scientifically valid, and the 

resulting claims are trustworthy. In addition, standards for methods or interpretation of 

results must include the expression and communication of the uncertainties in 

measurements or other results.
4

• Consensus Views – While this standard is correct to point out that it is 

inappropriate to provide point estimates alone, the proposed standard does not 

propagate various sources of error in a statistically meaningful way. As a result, 

the ranges obtained from the proposed method do not have a probabilistic 

meaning. There are several sources of uncertainty that may affect the calculations 

considered in this report: sampling bias, instrumental measurement error, and 

variation within the population. An approach grounded in statistical methods, 

such as measurement error research, could address these sources of error in a 

scientifically valid way.

• Consensus View – The ranges given for each of the pharmacokinetic parameters 

could suggest a rectangular distribution. And the references that establish these 

ranges are based on limited sample types and sizes. These limitations need to be 

mentioned for each parameter in sections 4.1.1 – 4.1.3, and Section 4.4 should 

include more cautionary language. 

• Minority View – None.

II. Human Factors: All forensic science methods rely on human performance in acquiring, 

examining, reporting, and testifying to the results. In the examination phase, some 

standards rely heavily on human judgment, whereas others rely more on properly 

maintained and calibrated instruments and statistical analysis of data.

• Consensus View – This standard adequately addresses this issue.

• Minority View – None.

III. Quality Assurance: Quality assurance covers a broad range of topics. For example, a 

method must include quality assurance procedures to ensure that sufficiently similar 

results will be obtained when the methodology is properly followed by different users in 

different facilities.

• Consensus View – Section 6.5 on postmortem samples would be clearer if 

combined with section 4.3 on specimen considerations. 

• Consensus View – Section 4.3.2 on urine could be strengthened as “not 

amenable” could be interpreted as “not ideal but still usable.” Similarly, section 

5.1.1 could include a “but not urine” clause.

• Consensus View – The measurement error for alcohol concentration will depend 

on the method of measurement. This standard assumes that alcohol concentration 

measured by either blood or breath will both have equivalently trivial degrees of 

measurement error. The standard should require the reporting of which method 

was used and the associated measurement error, if known. If the associated 

measurement error is not known, the standard should require this to be stated as 
5

well. Throughout the standard, alcohol concentrations are treated essentially as an 

exact number. This assumption needs justification. Requirements for alcohol 

concentration measurements need to be briefly listed or cited to ensure the results 

of the subsequent calculations are as precise as hoped. 

• Minority View – Experts are advised by this document to include the 

measurement uncertainty in their calculations when provided, but measurement 

uncertainty is not currently available for all test results, especially regarding

breath testing programs. Requirements for alcohol concentration measurement 

testing to ensure acceptable levels of precision is well outside the scope of this

guideline and should be addressed separately in documents focused on analytical 

guidelines, some of which are currently in process with ASB.

IV. Scope and Purpose: Standards should have a short statement of their scope and purpose. 

They should list the topics that they address and the related topics that they do not 

address. Requirements, recommendations, or statements of what is permitted or 

prohibited do not belong in this section.

• Consensus View – This standard adequately addresses this issue.

• Minority View – None.

V. Terminology: Standards should define terms that have specialized meanings. Rarely 

should they give a highly restricted or specialized meaning to a term in common use 

among the general public.

• Consensus View – Section 4.4 is titled “Uncertainty of Measurement” which 

suggests the precision of results of a single measurand. The content in this 

section, however, seems to have more to do with the variability of these 

parameters in a population. While both effects can propagate through subsequent 

calculations, they are not quite the same thing.

• Minority View – None.

VI. Method Description: There is no rule as to the necessary level of detail in the 

description of the method. Some parts of the method may be performed in alternative 

ways without affecting the quality and consistency of the results. Standards should focus 

on standardizing the steps that must be performed consistently across organizations to 

ensure equivalent results. Alternatively, standards can define specific performance 

criteria that must be demonstrated and met, rather than specifying the exact way a task 

must be done. For example, it may be sufficient to specify the lower limit of detection for

a substance without specifying the equipment or method for achieving it.

• Consensus View – Sections 4.1.2.1, 4.1.2.2, and 5.2.3 refer to an “anthropometric 

approach” that can be used to calculate Vd in lieu of the provided range. More 

information about this approach, ideally the actual equations, needs to be 
6

provided. Maskell seems partial to two equations, “The results from the present 

study seem to favour the anthropometric equations published by Forrest [9] and 

Watson et al. [6].” These equations are simple and straightforward; including 

them in the standard would not be too onerous. Further, perhaps this standard, 

should recommend only these two favored methods. At a minimum, some 

discussion is needed about the effect of the anthropometric approach on Vd values 

(i.e., could they fall outside of the prescribed Vd range?). Perhaps, an example 

could be added to the appendix where this anthropometric approach is used. 

• Minority View – None.

VII. Reporting Results: Methods must not only be well described, scientifically sound, and 

comprehensive but also lead to reported results that are within the scope of the standard, 

appropriately caveated, and not overreaching.

• Consensus View – The ranges for the pharmacokinetic parameters, previously 

discussed, could lead to reports with results that could be misinterpreted that 

extreme values are as probable as more central values. 

• Minority View – The probability of where an individual subject would likely fall 

within the calculated range is dependent on a number of factors and would be 

open to interpretation by the expert. Interpretation of results is outside the scope 

of this document and is addressed, to some extent, in ANSI/ASB 037 'Guidelines 

for Opinions and Testimony in Forensic Toxicology'. Applying a full range as 

stated in this document reduces the possibility that an expert will inadvertently 

exclude possible concentrations by applying a certainty to the midpoint that does 

not exist.