Academic Journal
View in EDS

Assessing uncertainty in forensic alcohol calculations: The case for using percentile ranges.

Bibliographic Details
Title: Assessing uncertainty in forensic alcohol calculations: The case for using percentile ranges.
Authors: Maskell PD; SPA Forensic Services, Govan, Glasgow, UK.; Forensic Medicine and Science, University of Glasgow, Glasgow, UK., Fitsanakis VA; Department of Drug Discovery and Biomedical Sciences, College of Pharmacy, Medical University of South Carolina, Charleston, South Carolina, USA.; Toxicology Group, Robson Forensic, Inc., Lancaster, Pennsylvania, USA., LeBeau MA; LeBeau Forensic Toxicology Consulting, O'Fallon, Missouri, USA., Castillo LV; School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh, UK., Wilson AL; School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh, UK.
Source: Journal of forensic sciences [J Forensic Sci] 2026 Jul; Vol. 71 (4), pp. 1793-1801. Date of Electronic Publication: 2026 Apr 19.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: Blackwell Pub Country of Publication: United States NLM ID: 0375370 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1556-4029 (Electronic) Linking ISSN: 00221198 NLM ISO Abbreviation: J Forensic Sci Subsets: MEDLINE
Imprint Name(s): Publication: 2006- : Malden, MA : Blackwell Pub.
Original Publication: [Chicago, Ill.] : Callaghan and Co., 1956-
MeSH Terms: Ethanol*/pharmacokinetics , Ethanol*/analysis , Central Nervous System Depressants*/pharmacokinetics , Central Nervous System Depressants*/analysis , Alcohol Drinking*, Humans ; Uncertainty ; Blood Alcohol Content ; Forensic Toxicology ; Breath Tests
Abstract: Forensic alcohol calculations are used to determine the amount of alcohol consumed based on (a) a relevant biological sample (i.e., breath or blood), (b) the blood alcohol concentration after a certain period following the consumption of a known quantity of alcohol, or (c) the extrapolation of the analytical result of an alcohol analysis to a legally relevant time. Current best practice guidelines recommend the use of percentile ranges for the parameters that contribute the most uncertainty to the results derived from forensic alcohol calculations. These parameters are volume of distribution (Vd) and elimination rate of alcohol (β). To date, there has been a lack of a transparent and defensible framework for using percentile ranges in forensic alcohol calculations. This work uses simulated data and statistical principles to demonstrate both why and what percentile ranges should be used in forensic alcohol calculations. We recommend that the percentile range used should depend on the case type (civil vs. criminal) and the amount of data available. The percentile ranges should be determined from an appropriate population using bootstrapping to estimate the relevant percentile with a two-tailed 95% confidence interval: for civil cases (25th and 75th percentiles; 50% range) and for criminal cases (0.5th and 99.5th percentiles; 99% range or 2.5th and 97.5th percentiles; 95% range) depending on the amount of data available. Using relevant percentile ranges produces results that better reflect the underlying uncertainty in a specific case than using a population average when carrying out forensic alcohol calculations.
(© 2026 American Academy of Forensic Sciences.)
References: Jones AW, Tilson C. Distribution ratios of ethanol and water between whole blood, plasma, serum, and erythrocytes: recommendations for interpreting clinical laboratory results in a legal context. J Forensic Sci. 2023;68(1):9–21. https://doi.org/10.1111/1556‐4029.15164.
Maskell PD, Cooper GAA. Uncertainty in Widmark equation calculations: volume of distribution and body mass. J Forensic Sci. 2020;65(5):1676–1684. https://doi.org/10.1111/1556‐4029.14447.
Widmark EM. Principles and applications of medicolegal alcohol determinations. Davis, CA: Biomedical Publications; 1981.
Gullberg RG. Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology. Forensic Sci Int. 2007;172(1):33–39. https://doi.org/10.1016/j.forsciint.2006.11.010.
Searle J. Alcohol calculations and their uncertainty. Med Sci Law. 2015;55(1):58–64. https://doi.org/10.1177/0025802414524385.
Maskell PD, Alex Speers R, Maskell DL. Improving uncertainty in Widmark equation calculations: alcohol volume, strength and density. Sci Justice. 2017;57(5):321–330. https://doi.org/10.1016/j.scijus.2017.05.006.
Academy Standards Board. Best practice recommendation for performing alcohol calculations in forensic toxicology (ANSI/ASB 122); 2024. [cited 2026 Mar 3]. Available from: https://www.aafs.org/sites/default/files/media/documents/122_BPR_e1.pdf.
Maskell PD, Johnson A, Scott‐Ham M. UKIAFT guidelines for alcohol calculations V4.4; 2024. [cited 2026 Mar 3]. Available from: https://www.ukiaft.org/wp‐content/uploads/ukiaft‐atd‐v4.4.pdf.
Maskell PD, Korb AS. Revised equations allowing the estimation of the uncertainty associated with the total body water version of the Widmark equation. J Forensic Sci. 2022;67(1):358–362. https://doi.org/10.1111/1556‐4029.14859.
Jones AW. Evidence‐based survey of the elimination rates of ethanol from blood with applications in forensic casework. Forensic Sci Int. 2010;200(1–3):1–20. https://doi.org/10.1016/j.forsciint.2010.02.021.
Jones AW, Andersson L. Influence of age, gender, and blood‐alcohol concentration on the disappearance rate of alcohol from blood in drinking drivers. J Forensic Sci. 1996;41(6):922–926. https://doi.org/10.1520/JFS14026J.
Viti A, Terzi A, Bertolaccini L. A practical overview on probability distributions. J Thorac Dis. 2015;7(3):E7–E10. https://doi.org/10.3978/J.ISSN.2072‐1439.2015.01.37.
Jones AW. The variability of the blood/breath ratio and its impact on the results of breath‐alcohol analyses: a rejoinder. J Chem Educ. 2024;101(3):715–717. https://doi.org/10.1021/ACS.JCHEMED.3C01206/.
Labianca DA. The variability of the blood/breath ratio and its impact on the results of breath‐alcohol analyses. J Chem Educ. 2023;100(11):4166–4167. https://doi.org/10.1021/ACS.JCHEMED.3C00742.
Saskőy L, Taylor L, Rooney B, Trotter G. Back to the future: retrograde alcohol calculations an uncertain science. Sci Justice. 2024;64(5):455–459. https://doi.org/10.1016/J.SCIJUS.2024.06.005.
Leubsdorf J. The surprising history of the preponderance standard of civil proof. Fla L Rev. 2015;67(5). [cited 2026 Mar 3]. Available from: https://scholarship.law.ufl.edu/flr/vol67/iss5/2.
Pi D, Parisi F, Luppi B. Quantifying reasonable doubt. Rutgers L Rev. 2019;72(2):455–508. Available from: https://rutgerslawreview.com/wp‐content/uploads/2020/11/72_Rutgers_Univ_L_Rev_0455_Pi_Parisi_Luppi.pdf.
Franklin J. Case comment—United States v. Copeland, 369 F. Supp. 2d 275 (E.D.N.Y. 2005): quantification of the ‘proof beyond reasonable doubt’ standard. Law Probab Risk. 2006;5(2):159–165. https://doi.org/10.1093/LPR/MGL017.
Victor v. Nebraska | 511 U.S. 1 (1994) | Justia U.S. Supreme Court Center. [cited 2025 May 20]. Available from: https://supreme.justia.com/cases/federal/us/511/1/.
Hansberry HL, Canan RF, Cannon M, Seltzer R. Legal standards by the numbers. Judicature. 2016;100(1):57–66. Available from: https://judicature.duke.edu/articles/legal‐standards‐by‐the‐numbers/.
Fell JC, Voas RB. The effectiveness of a 0.05 blood alcohol concentration (BAC) limit for driving in the United States. Addiction. 2014;109(6):869–874. https://doi.org/10.1111/ADD.12365.
Blomberg RD, Peck RC, Moskowitz H, Burns M, Fiorentino D. The Long Beach/Fort Lauderdale relative risk study. J Safety Res. 2009;40(4):285–292. https://doi.org/10.1016/J.JSR.2009.07.002.
Cheng WJ, Chen LY, Fang SC, Chang HM, Yang TW, Chang RC, et al. Examining factors associated with postintervention recidivism in DUI repeat offenders after alcohol treatment: one‐year follow‐up study. J Subst Abuse Treat. 2021;130:108426. https://doi.org/10.1016/J.JSAT.2021.108426.
Nochajski TH, Stasiewicz PR. Relapse to driving under the influence (DUI): a review. Clin Psychol Rev. 2006;26(2):179–195. https://doi.org/10.1016/J.CPR.2005.11.006.
Fell JC, Tippetts AS, Voas RB. Fatal traffic crashes involving drinking drivers: what have we learned? Ann Adv Automot Med. 2009;53:63–76.
Dickson MF, Wasarhaley NE, Webster JM. A comparison of first‐time and repeat rural DUI offenders. J Offender Rehabil. 2013;52(6):421–437. https://doi.org/10.1080/10509674.2013.813616.
Horowitz GL, Altaie S, Boyd JC, Ceriotti F, Garg U, Horn P, et al. EP28‐A3c: defining, establishing, and verifying reference intervals in the clinical laboratory; approved guideline. 3rd ed. Malvern, PA: Clinical and Laboratory Standards Institute; 2010.
R Core Team. R: A language and environment for statistical computing; 2022. [cited 2026 Mar 3]. Available from: https://www.r‐project.org/.
Canty A, Ripley B. Bootstrap functions [R package boot version 1.3‐32]. CRAN: Contributed Packages. 2025. https://doi.org/10.32614/CRAN.PACKAGE.BOOT.
Heumann C, Schomaker M, Shalabh. Introduction to statistics and data analysis: with exercises, solutions and applications in R. 2nd ed. Cham, Switzlernad: Springer; 2023. https://doi.org/10.1007/978‐3‐031‐11833‐3/COVER.
Solberg HE. Approved recommendation (1986) on the theory of reference values. Part 1. The concept of reference values. Clin Chim Acta. 1987;165(1):111–118. https://doi.org/10.1016/0009‐8981(87)90224‐5.
PetitClerc C, Solberg HE. Approved recommendation (1987) on the theory of reference values. Part 2. Selection of individuals for the production of reference values. Clin Chim Acta. 1987;170(2–3):S1–S11. https://doi.org/10.1016/0009‐8981(87)90150‐1.
Contributed Indexing: Keywords: Widmark; alcohol (ethanol); alcohol calculations; bootstrapping; burden of proof; retrograde extrapolation
Substance Nomenclature: 3K9958V90M (Ethanol)
0 (Central Nervous System Depressants)
0 (Blood Alcohol Content)
Entry Date(s): Date Created: 20260419 Date Completed: 20260707 Latest Revision: 20260707
Update Code: 20260708
DOI: 10.1111/1556-4029.70343
PMID: 42002526
Database: MEDLINE
Description
ISSN:1556-4029
DOI:10.1111/1556-4029.70343