2020-S-0003 Guidelines for Performing Alcohol Calculations

in Forensic Toxicology

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OSAC 2020-S-0003

Guidelines for Performing 

Alcohol Calculations in 

Forensic Toxicology

Forensic Toxicology Subcommittee

Chemistry: Seized Drugs & Toxicology Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
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Draft OSAC Proposed Standard

OSAC 2020-S-0003

Guidelines for Performing Alcohol 

Calculations in Forensic Toxicology

Prepared by 

Forensic Toxicology Subcommittee

May 2021

Disclaimer:

This OSAC Proposed Standard was written by the Forensic Toxicology Subcommittee of the 

Organization of Scientific Area Committees (OSAC) for Forensic Science following a process that 

includes an open comment period. This Proposed Standard will be submitted to a standards 

developing organization and is subject to change. 

There may be references in an OSAC Proposed Standard to other publications under development by 

OSAC. The information in the Proposed Standard, and underlying concepts and methodologies, may 

be used by the forensic-science community before the completion of such companion publications.

Any identification of commercial equipment, instruments, or materials in the Proposed Standard is 

not a recommendation or endorsement by the U.S. Government and does not imply that the 

equipment, instruments, or materials are necessarily the best available for the purpose.

To be placed on the OSAC Registry, certain types of standards first must be reviewed by a Scientific 

and Technical Review Panel (STRP). The STRP process is vital to OSAC’s mission of

generating and recognizing scientifically sound standards for producing and interpreting forensic

science results. The STRP shall provide critical and knowledgeable reviews of draft standards or of 

proposed revisions of standards previously published by standards developing organizations (SDOs) 

to ensure that the published methods that practitioners employ are scientifically valid, and the 

resulting claims are trustworthy.

The STRP panel will consist of an independent and diverse panel, including subject matter experts, 

human factors scientists, quality assurance personnel, and legal experts, which will be tasked with 

evaluating the proposed standard based on a comprehensive list of science-based criteria. 
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For more information about this important process, please visit our website at: 

https://www.nist.gov/topics/organization-scientific-area-committees-forensic-science/scientifictechnical-review-panels
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1 Guidelines for Performing Alcohol Calculations in Forensic Toxicology

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3 Foreword

4 Forensic toxicologists and other experts are frequently requested to perform calculations related to 

5 alcohol (ethanol), but there can be a high degree of variability in how this work is performed. 

6 Adherence to this guideline will improve the quality and consistency of this type of work that could 

7 mitigate the risk for bias.

8

9 There are numerous factors that must be taken into consideration when providing estimates related to 

10 alcohol consumption and alcohol concentrations. Alcohol pharmacokinetics vary within the 

11 population, but also within an individual. A person’s exact volume of distribution and elimination rate 

12 at a given time cannot be known. Many forensic blood alcohol results are based on replicate analyses 

13 and are reported with an estimation of measurement uncertainty, however, many other results (e.g. 

14 breath tests, medical tests) do not provide an uncertainty. Other factors in the process, such as time 

15 and weight, may have unknown degrees of accuracy associated with them, depending on the source of 

16 the information. These factors do not prohibit reasonable estimates from being determined, but do 

17 require experts to be conservative, knowledgeable about the limitations, and thorough in their work. 

18 The expert should not overstate the interpretation of their calculations; nor should they oversimplify 

19 the process.

20

21 The approach taken in this guideline is to provide a reasonable estimate of the range which 

22 encompasses the value of interest, and then apply that range to the question at hand, with 

23 consideration of the assumptions that may/may not be made. For example, in a situation where there 

24 is a long delay between the incident and the blood draw, an expert may be asked what the subject’s 

25 blood alcohol concentration was at the time of the incident. Due to the factors discussed within this 

26 guideline, the science does not support being able to provide a single value. Rather an estimated range 

27 can be provided and applied to the case at hand, while clearly stating any assumptions that may impact 

28 that application. The range does not put any greater likelihood that the subject was at the high or low 

29 end of the range, nor that they were likely in the middle. The Appendix illustrates how this approach 

30 can be applied in various scenarios.

31

32 Future editions of this guideline will work toward applying a statistical approach to the calculations. 

33 There are approaches in the literature that provide estimated uncertainties for some of the variables 

34 contained within the calculations. For example, for elimination rate and volume of distribution, there is 
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35 a significant amount of scientific literature that one may be able to reasonably estimate an average with 

36 an associated uncertainty. The body of knowledge in the peer reviewed literature is continually 

37 increasing and may eventually allow for estimations of the variances associated with all the 

38 parameters. 

39

40 Personnel and training requirements are outside the scope of this guideline. It is expected that persons 

41 performing this type of work have an understanding of pharmacokinetics, along with relevant 

42 education and experience. 

43

44 Keywords

45 Alcohol (ethanol), retrograde extrapolation, pharmacokinetics

46

47 Table of Contents

48

49 1. Scope

50 This document provides guidelines for performing alcohol (ethanol) calculations. Guidance on 

51 calculations for retrograde extrapolation, forward estimations, minimum drinks consumed, and 

52 other typical situations are addressed. Recommendations are provided for evaluation of post 

53 absorptive stage, various specimen types, and population variances. Reporting of calculations is 

54 also addressed. This guideline is intended for an expert performing alcohol calculations, whether 

55 as an employee of a public or private laboratory, or as an independent forensic service provider. It 

56 applies to matters related to criminal and/or civil proceedings.

57

58 2. Normative References - Required references for using this guideline

59 Maskell, P., Jones, W., Savage, A., and Scott-Ham, M. Evidence based survey of the distribution volume 

60 of ethanol; comparison of empirically determined values with anthropometric measures. Forensic 

61 Science International, 2019.

62 Jones, A.W. Pharmacokinetics of ethanol – Issues of forensic importance, Forensic Science Review, 

63 2011.

64

65 3. Terms and Definitions

66 3.1. Alcohol = ethanol

67

68 4. Background Information
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69 4.1. Alcohol Pharmacokinetics

70 The mechanisms of absorption, distribution, and elimination of alcohol throughout the body 

71 must be considered when performing alcohol calculations.

72 4.1.1. Absorption

73 The absorption of alcohol is a complex dynamic process that begins as soon as drinking 

74 begins. Alcohol is primarily absorbed into the blood stream through the small intestine, 

75 but some absorption occurs in the stomach and mouth. Absorption rates are highly 

76 variable and are not linear. Factors such as the presence of food in the stomach, the 

77 type and volume of beverage consumed, other drugs consumed, and the condition of the 

78 gastrointestinal tract, can impact the rate of absorption. Studies support that it can take 

79 up to 2 hours for complete absorption after the last drink. (2-4, 7-9, 12, 14-16, 19, 23,

80 24, 30, 31, 34) The time needed to reach the peak alcohol concentration (AC) is not the 

81 same as the time to complete absorption.

82 4.1.2. Distribution

83 Alcohol is water soluble and rapidly distributed throughout the total body water by the 

84 blood supply. For alcohol, the volume of distribution (Vd) is closely correlated with the 

85 total body water. Numerous factors impact an individual’s Vd including sex, body mass 

86 index (BMI), and age. In general, Vd is typically lower for women, obese individuals, and 

87 the elderly. Numerous publications propose mathematical approaches to estimate an 

88 individual’s Vd based on certain factors (height, weight, sex), and attempt to provide 

89 ranges for the Vd of alcohol. (5, 18, 25, 28, 29) However, there are significant 

90 limitations to these studies. For example, the number of participants in many studies is 

91 quite small, and the participants tend to be Western European and Caucasian, with 

92 limited variability of BMI and age. There are also differences in whether Vd, total body 

93 water, or rho were measured. Some involved bolus drinking, while others used a social 

94 drinking scenario. Alcohol concentration may have been measured in whole blood, 

95 serum/plasma, or breath. (5, 18, 25, 28, 29) Therefore, caution must be used when 

96 comparing, or attempting to average, these various formulas since they do not all 

97 calculate the same variable.

98 4.1.2.1 Research supports a range of 0.40 – 0.80 L/kg or an anthropometric approach 

99 (normative references 1 and 2). 

100 4.1.2.2 Maskell, et al (normative reference 1) determined the accuracy and precision of the 

101 various equations to estimate a subject’s Vd by applying them to a single data set 

102 compiled from six published studies. The authors provide suggested correction 
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103 factors for bias, along with confidence intervals for each model. This approach 

104 considers the subject’s individual factors, and provides a range of Vd values to apply 

105 in further calculations.

106 4.1.2.3 Due to the high variability among the population, the use of a single factor for Vd is 

107 inappropriate. 

108 4.1.3 Elimination

109 Alcohol is primarily eliminated via enzyme metabolism in the liver; however, a small 

110 amount is removed through first pass metabolism or excreted unchanged in the breath, 

111 sweat, oral fluid, and urine. Alcohol is eliminated at a constant, linear rate (zero order 

112 kinetics), until low concentrations are reached. 

113 4.1.3.1 An elimination rate range of 0.010 – 0.025 g/dL/hour encompasses the majority of 

114 the population regardless of age, sex, ethnicity, and drinking experience. (normative 

115 reference 2, and 10, 11, 13, 20, 21, 26, 32)

116 4.1.3.2 At concentrations below 0.030 g/dL, the elimination rate may not be linear as zero 

117 order kinetics may no longer apply. (1, 11)

118

119 4.2 Case History

120 The type of information, and source of that information, will vary from case to case. Experts 

121 should be clear as to the information they rely upon, and the assumptions they make. On 

122 occasion, that information may change as the case proceeds. 

123 4.2.1 Time: the time of the incident and the timing of drinking play a role in the

124 assumptions that can be made and the associated calculations. For example, 

125 the time of last drink based on video surveillance may be considered 

126 differently than a time based on the subject’s self-reported drinking history. 

127 This may impact the assessment of whether the subject was post absorptive 

128 at the time of the incident. 

129 4.2.2 Type of beverage: when there is evidence of the type of beverage consumed, it 

130 may be appropriate to calculate the number of drinks based on that 

131 information. However, in other situations, it may be more appropriate to 

132 reference a “standard drink” (see 4.5), such as when there is no history or the 

133 subject consumed unknown quantities of various types of drinks.

134

135 4.3 Specimen Considerations
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136 4.3.1 Serum and plasma have a higher water content than whole blood. Research supports a 

137 serum/plasma to blood ratio of 1.04 to 1.26. (6)

138 4.3.2 Urine is an elimination product which is influenced by hydration and time since last 

139 void. Results from urine alcohol testing are not amenable to extrapolation or other 

140 calculations, including urine results that have been converted to a whole blood 

141 equivalent.

142

143 4.4 Propagation of Uncertainty

144 The variance and distribution for all parameters used in the calculations has not been fully 

145 characterized in the scientific literature at this point. Therefore, as an initial minimum 

146 guideline, a statistical approach incorporating the uncertainties for each of the parameters is 

147 not presented. This guideline does not prohibit the expert from applying accepted statistical 

148 models within the calculations. These calculations should be clearly presented, with references 

149 or stated assumptions for the associated uncertainties and the method of determining the 

150 uncertainty. 

151 If known, the range associated with the measurement uncertainty of the test result may be 

152 incorporated.

153

154 4.5 Standard drink

155 A “standard drink” is defined as a beverage containing approximately 14 grams of alcohol. (33)

156 e.g. 12 ounces, 5% beer

157 5 ounces, 12% wine

158 1.5 ounces, 80 proof liquor (40%)

159

160 4.6 English/Metric conversions (if applicable)

161 Volume: 1 ounce = 29.6 mL

162 Weight: 1 pound = 0.454 kilograms

163 Height: 1 inch = 2.54 centimeters or 0.0254 meters

164

165 4.7 Density of alcohol = 0.789 g/mL

166

167 5 Calculations

168 5.1 Alcohol Test Results

169 5.1.1 Calculations presented are valid for both blood (g/dL) and breath (g/210L).
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170 5.1.2 Serum/plasma results shall be converted to a whole blood equivalent prior to other 

171 calculations. The range should be 1.04 to 1.26 serum/plasma to blood ratio. (6) Further 

172 calculations shall then be applied to both converted AC results.

173

174 5.2 Widmark’s Formula – the relationship between a dose of alcohol and a resulting alcohol 

175 concentration. 

176 Equation 1

177 where:

178 AC = alcohol concentration (g/L)

179 D = dose (g)

180 Vd = volume of distribution (L/kg)

181 w = weight (kg)

182

183 Variations of the formula can be applied to several common scenarios. 

184

185 Estimating the minimum number of drinks to achieve a particular alcohol concentration may be

186 used to support/refute a particular drinking history, or to establish that someone could not 

187 have consumed less than that amount of alcohol.

188 5.2.1 Minimum number of drinks to achieve a particular alcohol concentration:

189 This calculation does not account for any drinks eliminated. It provides an estimate of 

190 the equivalent dose of alcohol in the system at the time of the blood draw/breath test.

191 Equation 2: Minimum dose of alcohol

DD = AAAA × VVVV × ww × 10dddd 192 where:

193 D = dose (g)

194 AC = alcohol concentration (g/dL, g/210 L breath)

195 Vd = volume of distribution (L/kg)

196 w = weight (kg)

197 Equation 3: Using the calculated dose to estimate the minimum number of “drinks” 

198 when beverage concentration is known

VV = DD

× ρ × m

199

200 where:

201 V = volume (oz)

Vd w

D AC

* =
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202 D = dose (g)

203 C = beverage concentration (mL/100mL)

204 ρ = density of ethanol (0.789 g/mL)

205 m = metric conversion (29.6 mL/oz), if necessary

206

207 The calculated volume can be converted to the equivalent number of drinks, depending 

208 on the type of drink. e.g. If the subject was drinking 12 oz beers, a volume of 37 oz 

209 would be equivalent to ~ 3 beers.

210

211 5.2.2 Maximum alcohol concentration that could theoretically be achieved from a given dose:

212 These calculations provide the maximum AC attainable from a reported number of 

213 consumed drinks. They are used to support/refute a particular drinking history. The 

214 calculations are used to attempt to answer the question: “If someone had X number of 

215 drinks, could they have reached the measured AC?” The calculated results can also 

216 provide information to account for potentially unabsorbed alcohol or post incident 

217 alcohol consumption. 

218

219 Equation 4: Dose of alcohol from a drink

220 DD = VV × × ρ × mm

221 where:

222 D = dose (g)

223 V = volume (oz)

224 C = beverage concentration (mL/100mL)

225 ρ = density of ethanol (0.789 g/mL)

226 m = metric conversion (29.6 mL/oz), if necessary

227

228 Equation 5: Theoretical maximum AC from a given drink(s)

229 This calculation provides the theoretical maximum alcohol concentration. It assumes full 

230 absorption with no elimination.

ACdddddddddd(ss) = DD

VVVV × ww × 10 dddd 231

232 where:

233 ACdrink(s) = max alcohol concentration (g/dL) from a drink(s)

234 D = dose (g)
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235 Vd = volume of distribution (L/kg)

236 w = weight (kg)

237

238 5.2.3 A range shall be used for Vd in the calculations; either a range of 0.40-0.80 L/kg, or the

239 calculated range using an anthropometric approach (see 4.1.2.1).

240 5.2.4 See A.1 for examples

241

242 5.3 Retrograde Extrapolation

243 Retrograde extrapolation is a mathematical process that uses an alcohol concentration at a given 

244 point in time and estimates what the concentration would have been at an earlier time.

245 NOTE: It is not possible to calculate the exact alcohol concentration at an earlier point in time, but

246 an estimation in the form of a range of concentrations can be provided. 

247 5.3.1 Basic Calculation

248 Equation 6:

249 AAAA ii = AAAAtttt tt + (RR × TT)

250 where:

251 ACinc = estimated alcohol concentration at the time of the incident (g/dL)

252 ACtest = measured alcohol concentration (g/dL)

253 R = elimination rate (g/dL/hour)

254 T = time between incident and time of breath test/blood draw (hours)

255 5.3.2 Extrapolation shall not be performed on alcohol concentrations below 0.030 g/dL.

256 5.3.3 Elimination Rate Range

257 5.3.3.1 The calculation shall be performed using a range of elimination rates. The minimal 

258 range shall be 0.010 – 0.025 g/dL/hour.

259 5.3.3.2 An elimination rate calculated from two or more test results shall not be used in 

260 place of a range. 

261 5.3.4 Assessment of absorptive state

262 5.3.4.1 The impact of potentially unabsorbed alcohol shall be addressed. 

263 5.3.4.2 If the time of incident is more than 2 hours after the time of drinking cessation, it is

264 reasonable to assume the subject is post absorptive. See A.2 for example.

265 5.3.4.3 When the drinking history is unknown, it is not reasonable to assume that the 

266 subject is post absorptive. Additional calculations can be applied to assess the 

267 impact of potentially unabsorbed alcohol. See A.5 for example.
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268 5.3.4.4 If case history indicates that alcohol was consumed after the incident, but before the 

269 sample was obtained, this shall be accounted for in the estimates. 

270 5.3.4.5 An option to account for unabsorbed alcohol or post incident alcohol consumption is 

271 to subtract the impact of those drinks from the estimated post absorptive alcohol

272 concentrations (determined from Equation 6). See Equation 4 to calculate the 

273 maximum AC contribution from a drink. 

274 Equation 7:

275 Adjusted ACinc = ACinc – ACdrink(s)

276 where:

277 Adjusted ACinc = estimated AC at time of the incident, accounting for potentially 

278 unabsorbed alcohol or post incident alcohol consumption

279 ACinc = estimated AC at time of the incident if subject were in post absorptive 

280 state (calculated from Equation 6)

281 ACdrink(s) = maximum AC contribution from drink(s) (calculated from Equation 5)

282 Reference A.3 for example of subject not being post absorptive. See A.4 for example 

283 of post incident alcohol consumption.

284

285 6. Additional Considerations and Best Practice Recommendations

286 6.1 Documentation: Calculations should be documented, and assumptions clearly stated. This may 

287 be in the form of case notes, an electronic spreadsheet, a written report, etc.

288 6.2 Protocols: It is recommended that written protocols be in place to ensure the forensic service 

289 provider applies a consistent methodology to service requests. 

290 6.3 Technical Review: Where feasible, independent review of calculations by a qualified individual 

291 is encouraged.

292 6.4 Calculations during testimony: Performing alcohol calculations is a forensic service request, 

293 and should not be viewed as just a question during direct or cross examination, or “simple 

294 math” that the expert should be able to readily perform in their head. While the expert must 

295 respectfully follow the orders of the legal authorities overseeing the testimony (trial, 

296 deposition, etc), performing calculations during live testimony is discouraged due to the various 

297 risks to quality it may create. When so compelled, it is recommended that the witness 

298 document the additional work. Depending on the scope of the new work request and the 

299 complexity, the expert may consider requesting a brief recess to perform the work. In some 

300 circumstances, it may be appropriate to discuss the impact a change would have on the 
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301 calculations, rather than redoing them all, e.g. if the subject’s drinking history changes, one 

302 could state that it would raise/lower the estimated AC range provided. 

303 6.5 Postmortem specimens: The principles and practices outlined in this guideline may also apply 

304 to postmortem scenarios, but there are additional variables to be considered that are outside 

305 the scope of this guideline. (18,23)
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306 Appendix A (examples)

307

308 A.1. Support/refute drinking history

309 History: A 32 year old male subject was pulled over for suspected impaired driving. He had an 

310 evidential breath test result of 0.19g/210L. He stated he had been at a local bar for the last 3 hours and 

311 only had 2 pints of Brand X beer. He ate chicken wings and french fries.

312

313 Question: Is the stated drinking history consistent with the AC result?

314 This can be answered two different ways: by calculating the minimum number of drinks 

315 needed to attain a certain AC, or by calculating the maximum AC attainable from a drinking 

316 history.

317

318 Relevant Information: 

319 The subject is 6’1”, 230 lbs

320 Evidential breath test: 0.19g/210L

321 Alcohol content of Brand X beer ~4.3% (cite reference for that brand’s alcohol content (e.g. 

322 internet site and access date, published reference))

323 1 pint = 16oz

324

325 Calculations:

Weight conversion: ww = 230 llllll × 0.454 kkkk 326 llllll = 104 kkkk

327

328 A.1.1 What is the minimum number of drinks needed to reach a 0.19g/210L AC?

329 Using Equation 2 and a Vd range of 0.40-0.80 L/kg, calculate the dose needed:

DD = AAAA × VV × ww × 10dddd DD = AAAA × VVVV × ww × 10dddd 330

DD = 0.19dddd × 0.40kkkk × 104kkkk × 10dddd DD = 0.19dddd × 0.80kkkk 331 × 104kkkk ×

10dddd 332

333 D = 79g D = 158g

334 Using Equation 3, calculate the equivalent number of drinks for that dose: 

VV = DD

CC ×ρ ×m VV = DDCC ×ρ ×m 335

VV = 79gg

4.3 mm

100mm ×0.789mm ×29.6mmoooo

VV = 158gg

4.3 mm

100mm ×0.789mm ×29.6mmoooo

336

337 V = 79 oz V = 157 oz

338 Drinks = 79oz / 16oz = 5 pints Drinks = 157oz / 16oz = 10 pints
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339 Opinion: The subject’s stated drinking history is inconsistent with the breath test result. He had the 

340 equivalent of ~5-10 pints of Brand X beer in his system at the time of the test.

341

342 A.1.2 What is maximum AC that could be reached from 2 pints of Brand X beer?

343 Using Equation 4, calculate the dose from 2 pints of Brand X beer:

344 DD = VV × × ρ × mm

DD = 32oooo × 4.3 mm

100mm × 0.789 ggmm × 29.6mmoooo 345

346 D = 32g alcohol in 2 pints of Brand X

347

348 Using Equation 5 and a Vd range of 0.40-0.80 L/kg, calculate the maximum range of ACs this 

349 dose could theoretically reach:

ACdddddddddd(ss) = DD

VV ×ww ×10 dddd ACdddddddddd(ss) = DDVV ×ww ×10 dddd 350

ACdddddddddd(ss) = 32gg

0.40kkkk×104 ×10 dddd ACdddddddddd(ss) = 32gg0.80kkkk×104 ×10 dddd 351

352

353 ACdddddd (ss) = 0.077 / dd ACdddddddddd(ss) = 0.038 / dd

354 Opinion: The subject’s stated drinking history is inconsistent with the breath test result. If all the alcohol 

355 in 2 pints of Brand X were completely absorbed, and none eliminated, the maximum AC range achievable 

356 for the subject would be ~0.038-0.077 g/dL. 

357

358 A.2. Retrograde extrapolation, subject is post absorptive

359 History: A 45 year old woman was drinking wine at an out of town wedding. She left the wedding at 

360 6:00 pm, and had a five-hour drive home. At approximately 9:00 pm she crossed over the center line 

361 and crashed into an oncoming vehicle. She was injured and transported to the hospital; a blood kit was 

362 collected at 11:45 pm. The result of the blood test was 0.068g/dL. There were no alcoholic beverages 

363 in the vehicle. She stated she had not had anything to drink since leaving the wedding.

364

365 Question: What was her AC at the time of the crash? 

366

367 Relevant Information: 

368 The subject is 5’3”, 125 lbs

369 Blood alcohol: 0.068g/dL at 11:45 pm

370 Incident: 9:00 pm

371 Assumptions:
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372 Since there were at least 3 hours between the end of drinking and the incident, the subject is 

373 assumed to be post absorptive.

374 No post-incident alcohol consumption.

375

376 Calculations:

377 Elapsed Time = 9:00 pm to 11:45 pm = 2.75 hours

378

379 Using Equation 6 and an elimination rate range of 0.010-0.025 g/dL/hour, calculate AC range at 

380 time of incident:

AAAA ii = 0.068dddd + �0.010dddd/hoooooo × 2.75 hoooooo � = 0.096dddd 381

382 AAAA ii = AAAAtttt tt + (RR × TT)

AAAA ii = 0.068dddd + �0.025dddd/hoooooo × 2.75 hoooooo � = 0.137dddd 383

384

385 Opinion: It is estimated that the subject’s AC at the time of the incident was ~0.096-0.137 g/dL. Therefore, 

386 it is likely the subject was above the 0.08 g/dL legal limit at the time of the incident.

387

388 A.3. Retrograde extrapolation, subject is not post absorptive

389 History: A 22 year old female subject was drinking tequila shots at a bar. She paid her tab, took one last 

390 shot, and left the bar at ~11:00 pm. She crashed her car while trying to leave the parking lot. Her blood 

391 was drawn at 12:30 am and was a 0.082 g/dL. Her defense is that she was below 0.08g/dL at the time 

392 of the crash.

393

394 Question: Could the subject’s AC have been under 0.08 g/dL at the time of the crash?

395

396 Relevant Information:

397 The subject is 5’8”, 160lbs

398 Blood alcohol content: 0.082 g/dL at 12:30 am

399 Incident: 11:00 pm

400 80 proof = 40% alcohol concentration

401 Assumptions:

402 The alcohol from the last shot of tequila was not absorbed at the time of the incident.

403 Tequila is typically ~80 proof.

404

405 Calculations:
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406 Elapsed Time = 11:00 pm to 12:30 am = 1.5 hours

Weight conversion: ww = 160 llllll × 0.454 kkkk 407 llllll = 73 kkkk

408

409 Using Equation 6 and an elimination rate range of 0.010-0.025 g/dL/hour, calculate AC range at 

410 the time of incident, if the subject were post absorptive:

AAAA ii = 0.082dddd + �0.010dddd/hoooooo × 1.5 hoooooo � = 0.097dddd 411

412 AAAA ii = AAAAtttt tt + (RR × TT)

AAAA ii = 0.082dddd + �0.025dddd/hoooooo × 1.5 hoooooo � = 0.120dddd 413

414

415 Using Equation 4, calculate the dose of alcohol from a shot of tequila:

416 DD = VV × × ρ × mm

DD = 1.5oooo × 40 mm

100mm × 0.789 ggmm × 29.6mmoooo 417

418 D = 14g alcohol in shot of tequila

419

420 Using Equation 5 and a Vd range of 0.40-0.80 L/kg, calculate the maximum AC a tequila shot 

421 could contribute:

ACdddddddddd(ss) = DD

VV ×ww ×10 dddd ACdddddddddd(ss) = DDVV ×ww ×10 dddd 422

ACdddddddddd(ss) = 14gg

0.40kkkk×73 ×10 dddd ACdddddddddd(ss) = 14gg0.80kkkk×73 ×10 dddd 423

424 ACdddddddddd(ss) = 0.048 / dd ACdddddddddd(ss) = 0.024 / dd

425

426 Using Equation 7, adjust the AC to remove the theoretical maximum contribution the last shot 

427 could have contributed (using the calculated ranges of ACinc and ACdrink(s)):

428 Adjusted ACinc = 0.097 – 0.048 = 0.049g/dL

429 Adjusted ACinc = ACinc – ACdrink(s)

430 Adjusted ACinc = 0.120 – 0.024 = 0.096g/dL

431

432 Opinion: Assuming the last shot of tequila was not absorbed at the time of the incident, the subject’s AC at 

433 that time is estimated to be ~0.049 – 0.096g/dL. Therefore, it is possible she was below the 0.08 g/dL legal 

434 limit at the time of the incident.

435

436 A.4. Post incident consumption
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437 History: A 55 year old man drove his vehicle through his garage door at ~6:00 pm. A neighbor 

438 witnessed the crash and called the police. When the police arrived at the home, the subject greeted 

439 them with a partially consumed bottle of vodka in his hand (80 proof, 750 mL), and he appeared to be 

440 intoxicated. He was arrested for suspected DUI and had a breath test result of 0.215 g/210L. The 

441 defendant claimed he had not been drinking prior to the crash, and that his AC was from the vodka 

442 consumption after the crash. He claimed it was a new bottle; approximately one-third was missing.

443

444 Question: Could the consumption of 1/3 bottle of vodka account for the measured AC?

445

446 Relevant Information:

447 The subject is 5’10”, 210 lbs

448 Breath test result: 0.215g/210L

449 80 proof = 40% alcohol concentration

450

451 Calculations:

Weight conversion: ww = 210 llllll × 0.454 kkkk 452 llllll = 95 kkkk

AAmount consumed = 750 mm xx

1

3

453 = 250 mm

454

455 Using Equation 4, calculate the dose of alcohol from the vodka

456 DD = VV × × ρ (metric conversion not needed)

DD = 250mm × 40 mm

100mm × 0.789 ggmm 457

458 D = 79g alcohol in 1⁄3 bottle of vodka

459

460 Using Equation 5 and a Vd range of 0.40-0.80 L/kg, calculate the maximum AC the vodka could 

461 contribute:

ACdddddddddd(ss) = DD

VV ×ww ×10 dddd ACdddddddddd(ss) = DDVV ×ww ×10 dddd 462

ACdddddddddd(ss) = 79gg

0.40kkkk×95 ×10 dddd ACdddddddddd(ss) = 79gg0.80kkkk×95 ×10 dddd 463

464 ACdddddddddd(ss) = 0.208 / dd ACdddddddddd(ss) = 0.104 / dd

465

466 Using Equation 7, adjust the AC to remove the contribution from post-incident alcohol 

467 consumption (using the calculated ACdrink(s) range): 

468 = 0.215 –0.208 = 0.007g/dL
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469 Adjusted ACinc = ACinc – ACdrink(s)

470 = 0.215 –0.104 = 0.111g/dL

471

472 Opinion: If all the alcohol from the 1/3 bottle of vodka were completely absorbed, and none eliminated, the 

473 maximum AC range achievable for the subject would be ~0.104-0.208g/dL. Complete absorption with no 

474 elimination is not realistic, and the theoretical maximum AC range falls below the measured AC, therefore 

475 the subject’s drinking history is inconsistent. There was likely alcohol consumption prior to the incident. 

476

477 A.5 Minimal case history available

478 History: Subject is a 25-year-old female, 5’5”, 160 lbs. Crash at 1:00 am, blood draw at 3:00 am, blood 

479 test result 0.075g/dL. No drinking history available. 

480

481 Question: What was her AC at the time of the crash? 

482

483 Relevant Information

484 The subject is 5’5”, 160 lbs

485 “Standard” drink = 14g of alcohol

486 Assumptions:

487 With no drinking history, the impact of potentially unabsorbed alcohol is presented.

488 Since there is no information on the type of drinks, a standard drink will be used.

489

490 Calculations:

Weight conversion: ww = 160 llllll × 0.454 kkkk 491 llllll = 73 kkkk

492 Elapsed Time = 1:00 am to 3:00 am = 2 hours

493

494 Using Equation 6 and an elimination rate range of 0.010-0.025 g/dL/hour, calculate the AC at 

495 time of incident if post absorptive:

AAAA ii = 0.075dddd + �0.010dddd/hoooooo × 2 hoooooo � = 0.095dddd 496

497 AAAA ii = AAAAtt + (RR × TT)

AAAA ii = 0.075dddd + �0.025dddd/hoooooo × 2 hoooooo � = 0.125dddd 498

499

500 Using Equation 5 and a Vd range of 0.40-0.80 L/kg, calculate the maximun AC a “standard” 

501 drink could contribute:
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ACdddddddddd(ss) = DD

VV ×ww ×10 dddd ACdddddddddd(ss) = DDVV ×ww ×10 dddd 502

ACdddddddddd(ss) = 14gg

0.40kkkk×73 ×10 dddd ACdddddddddd(ss) = 14gg0.80kkkk×73 ×10 dddd 503

504 ACdd (ss) = 0.048 / dd ACdddddddddd(ss) = 0.024 / dd

505

506 Using Equation 7, adjust the AC to remove the number of drinks that would have to be 

507 unabsorbed to have the subject be below the legal limit at the time of the crash (using the 

508 calculated ranges of ACinc and ACdrink(s)):

509 Adjusted ACinc = ACinc – ACdrink(s)

510 Estimated AC @ 1:00am 0.010 rate 0.025 rate

511 Post absorptive (ACinc) 0.095 0.095 0.125 0.125

512 ACdrink(s) (Vd 0.40-0.80) 0.048 0.024 0.048 0.024

513 -1 drink unabsorbed 0.047 0.071 0.077 0.101

514 -2 drinks unabsorbed 0.077

515

516 Opinion: If the subject was post absorptive at the time of the incident, they were likely above the 0.08g/dL

517 legal limit at that time. However, if the subject had ~1-2 standard drinks unabsorbed at the time of the 

518 incident, they could have been below the 0.08g/dL legal limit.
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519 Annex B Bibliography (informative)

520

521 1. Caplan, Y., Goldberger, B. and Aguayo, E. Garriott's medicolegal aspects of alcohol. 6th ed. Lawyers & 

522 Judges Publication Company, Inc, 2014.

523 2. Charlton, S.G. and Starkey, N.J. Driver risk from blood alcohol levels between 50mg/100ml and 

524 80mg/100ml, NZ Transport Agency Research Report 541, 2013. 

525 3. Cowan, J., Weathermon, A., McCutcheon, J. and Oliver, R. Determination of Volume of Distribution for 

526 Ethanol in Male and Female Subjects. Journal of Analytical Toxicology, 1996.

527 4. Evaluation of Breath Alcohol Profiles and Testing the Reliability of Widmark calculations, Amy 

528 McElroy SDPD 2009

529 5. Forrest, A. The Estimation of Widmark's Factor. Journal of the Forensic Science Society, 1986.

530 6. Chalebois, R. et al. Comparison of Ethanol Concentrations in Blood, Serum, and Blood Cells for 

531 Forensic Application. Journal of Analytical Toxicology, 1996.

532 7. Ganert, P.M. and Bowthorpe, W.D. Evaluation of Breath Alcohol Profiles Following A Period of Social 

533 Drinking, Canadian Society of Forensic Science Journal, 2000.

534 8. Harger, R.N. Blood Source and Alcohol Level; Errors from Using Venous Blood During Active 

Absorption, Alcohol and Road Traffic Proceedings of 3rd 535 International Conference on Alcohol and 

536 Road Traffic, 1963. 

537 9. Jakus, J.T. and Shajani, N.K. and Image, B.A. Consumption of a Large Dose of Alcohol in a Short Time 

538 Span, Forensic Science International, 1992. 

539 10. Jones, A.W. Disappearance Rate of Ethanol from the Blood of Human Subjects: Implications in Forensic 

540 Toxicology. Journal of Forensic Sciences, 1993.

541 11. Jones, A.W. Evidence-based survey of the elimination rates of ethanol from blood. Forensic Science

542 International, 2010.

543 12. Jones, A.W. Interindividual Variations in the Disposition and Metabolism of Ethanol in Healthy Men, 

544 Alcohol, 1984.

545 13. Jones, A.W. and Andersson, L. Influence of Age, Gender, and Blood-Alcohol Concentration on the 

546 Disappearance Rate of Alcohol from Blood in Drinking Drivers, Journal of Forensic Sciences, 1996. 

547 14. Jones, A.W. and Jönsson, K.A. Food-Induced Lowering of Blood-Ethanol Profiles and Increased Rate 

548 Elimination Immediately After a Meal, Journal of Forensic Sciences, 1994. 

549 15. Jones, A.W. and Neri, A. Evaluation of Blood-Ethanol Profiles after Consumption of Alcohol Together 

550 with a Large Meal, Canadian Society of Forensic Science Journal, 1991. 
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551 16. Jones, A.W. and Wigmore, J.G. and House, C.J. The Course of the Blood-Alcohol Curve After 

552 Consumption of Large Amounts of Alcohol under Realistic Conditions, Canadian Society of Forensic 

553 Science Journal, 2006.

554 17. Kugelberg, F.C., Jones, A.W. Interpreting Results of Ethanol Analysis in Postmortem Specimens: A 

555 review of the literature. Forensic Science International, 2007.

556 18. Maudens, K., Patteet, L., van Nuijs, A., Van Broekhoven, C., Covaci, A. and Neels, H. The influence of 

557 the body mass index (BMI) on the volume of distribution of ethanol. Forensic Science International, 

558 2014.

559 19. McElrea, A. and Su, C. and Smith, L. Truncation of Breath Alcohol Measurements and Its Effect on Peak 

560 Concentrations, Journal of the Canadian Society of Forensic Science, 2011.

561 20. Montgomery, Mark, Reasor, Mark. Retrograde Extrapolation of Blood Alcohol Data: An Applied 

562 Approach. Journal of Toxicology and Environmental Health, 1992.

563 21. Neuteboom, W., Jones, A.W. Disappearance Rate of Alcohol from the Blood of Drunk Drivers 

564 Calculated from Two Consecutive Samples; What do the Results Really Mean? Forensic Science 

565 International, 1990.

566 22. O'Neal, C.L., Poklis, A. Postmortem production of ethanol and factors that influence interpretation: a 

567 critical review. American Journal of Forensic Medicine and Pathology, 1996. 

568 23. San Diego Police Department Crime Lab, Alcohol Section Training Studies (pending ToxTalk 

569 publication), 2006

570 24. San Diego Sheriff's Regional Crime Laboratory, Alcohol Section Training Studies (pending ToxTalk 

571 publication), 2012-2018

572 25. Seidl, S., Jensen, U. and Alt, A. The calculation of blood ethanol concentrations in males and females.

573 International Journal of Legal Medicine, 2000.

574 26. Stowell, A.R., Stowell, L.I. Estimation of Blood Alcohol Concentrations After Social Drinking. Journal 

575 of Forensic Sciences, 1998.

576 27. UKIAFT 2019. UKIAFT Guidelines for Performing Alcohol Technical Defence Calculations – version 

577 3.0

578 28. Ulrich, L., Cramer, Y., Zink, P. Relevance of individual parameters in the calculation of blood alcohol 

579 levels in relation to the volume of intake | Die Berücksichtigung individueller Parameter bei der 

580 Errechnung des Blutalkoholgehaltes aus der Trinkmenge., Blutalkohol, 1987.

581 29. Watson, P., Watson, I. and Batt, R. Prediction of blood alcohol concentrations in human subjects. 

582 Updating the Widmark Equation. Journal of Studies on Alcohol, 1981.

583 30. Watkins, Richard L. and Adler, Eugene V. The Effect of Food on Alcohol Absorption and Elimination 

584 Patterns, Journal of Forensic Sciences, 1993.
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585 31. Winek, Charles L. and Wahba, Wagdy W. and Dowdell, Jody L. Determination of Absorption time of 

586 Ethanol in Social Drinkers, Forensic Science International, 1996

587 32. Winek, C., Murphy, K. The Rate and Kinetic Order of Ethanol Elimination. Forensic Science 

588 International, 1984

589 33. “What Is A Standard Drink?” National Institute on Alcohol Abuse and Alcoholism, U.S. Department of 

590 Health and Human Services, www.niaaa.nih.gov/alcohol-health/overview-alcohol591 consumption/what-standard-drink, 09 Apr. 2018. 

592 34. Yang, Chi-ting. A study of alcohol pharmacokinetic of local Chinese in Hong Kong, University of Hong 

593 Kong, 2003.