ANSI/ASB Best Practice Recommendation 122, First Edition 2024, Best Practice Recommendation for Performing Alcohol Calculations in Forensic Toxicology, was added to the OSAC Registry on 1 October 2024. It supersedes OSAC 2020-S-0003. It governs retrograde extrapolation, forward estimation, minimum drinks consumed, post-absorptive evaluation, population variance, and the reporting of calculations.
The standard specifies what a defensible alcohol calculation must contain. It does not specify how to produce one. Most practitioners are meeting it with a spreadsheet, which means every calculation carries whatever assumptions were typed into it that day, and every report requires the analyst to reconstruct those assumptions on cross examination.
Below is a clause by clause mapping of the requirements in ASB 122 to the behavior of DUI Professional. Each row cites the clause. Where the standard uses shall, conformance is mandatory. Where it uses should, we note our default and whether it is configurable.
Requirement mapping
| ASB 122 clause | Requirement | DUI Professional |
|---|---|---|
| 5.2.2 | Fixed Vd by sex should be 0.58 to 0.83 L/kg male, 0.43 to 0.73 L/kg female. Sex independent fixed Vd should be 0.45 to 0.81 L/kg. | Both range sets available. Sex independent 0.45 to 0.81 L/kg is the default in the ASB Forensic Range model. |
| 4.1.3.2 | Research supports the above Vd ranges. | Cited in the model documentation shipped with every report. |
| 5.2.2 (individualized) | Individualized Vd should use Watson total body water and Maskell equations. | Watson TBW model included in Standard tier. |
| 5.4.4.1 | The elimination rate range shall be a minimum of 0.010 to 0.025 g/dL/hour. | Enforced as the floor. Narrower ranges cannot be entered without an explicit override that is recorded in the report. |
| 4.1.4.2 | That range encompasses the majority of the population regardless of age, sex, ethnicity, and drinking experience. | Reproduced in the report methodology section. |
| Retrograde extrapolation | Shall use a range of elimination rates, not a point value. | The software has no single rate mode for retrograde extrapolation. |
| Retrograde extrapolation | An elimination rate derived from two or more test results shall not substitute for the range. | Two point derived rates are reported as an observation, never substituted into the extrapolation. |
| Retrograde extrapolation | Shall not be performed on absorptive phase concentrations. | Absorptive phase inputs trigger a blocking warning naming the clause. |
| Specimen conversion | Serum or plasma to blood ratio shall be 1.13 to 1.19, and further calculations shall be applied to both converted values. | Both bounds carried forward through every downstream calculation. Single value conversion is not offered. |
| 6.1 | Documentation may take the form of case notes, an electronic spreadsheet, or a written report. | Every run produces a timestamped report containing the full assumption set, model selection, input provenance, and output ranges. |
What conformance does not mean
DUI Professional is a calculation and documentation tool. It does not interpret results, it does not offer an opinion, and it cannot be qualified as an expert. Conformance to ASB 122 means the arithmetic and the reporting meet the standard. The judgment about which model applies to a given case, and what the result means, remains the analyst's.
Verify it yourself
The standard is published at no cost by the AAFS Academy Standards Board. Read it, then open a free evaluation account and run the worked examples in Annex A. If any row above does not hold, tell us and we will correct the software or correct the page.
DUI Professional does not determine guilt, impairment, admissibility, or the legal sufficiency of evidence. It provides structured blood alcohol calculation and report support for qualified professional review.
Run the standard against your own case work
Open a free evaluation account, run the Annex A worked examples, and compare the output against what your current spreadsheet produces.
Sources
These references support the scientific and forensic context discussed on this page.
- ANSI/ASB Best Practice Recommendation 122, First Edition 2024 Current forensic alcohol calculation guidance for assumption-based alcohol calculations, reporting, specimen considerations, and limitations.
- NIST OSAC Standards Library entry for ANSI/ASB BPR 122-24 Registry context for ANSI/ASB Best Practice Recommendation 122-24.
- OSAC 2020-S-0003, Guidelines for Performing Alcohol Calculations in Forensic Toxicology Legacy proposed-standard context for forensic alcohol calculation scope, dose conversion, distribution-volume ranges, elimination-rate ranges, and cautions around absorption and reporting uncertainty.
- UKIAFT Alcohol Calculation Guidelines v4.4 Alcohol calculation guidance for total body water, elimination ranges, low-BAC caution, and clear reporting of assumptions.
- Watson, Watson, and Batt, Total body water volumes, 1980 Anthropometric equations for estimating total body water from age, height, weight, and sex-specific calculation basis.
- Maskell et al., Total body water in forensic blood-alcohol calculations, 2020 Forensic comparison of total-body-water approaches and volume-of-distribution approaches for blood-alcohol calculations.
- Jones, A.W., Evidence-based survey of ethanol elimination rates, 2010 Forensic context for ethanol elimination-rate variation and retrograde extrapolation review.
