DUI defenders facing prosecution toxicologist testimony estimating BAC at time of driving.

Daubert Challenge, Retrograde BAC Extrapolation

FRE 702 motion + cross-exam bank to limit prosecution retrograde-BAC testimony. Widmark-formula limits + AAFS critique grounded.

File a Daubert / motion in limine to exclude retrograde extrapolation testimony when the prosecution lacks the absorption-phase data the Widmark formula requires.

“Extrapolation back from the BAC at the time of testing to the BAC at the time of driving is an endeavor fraught with the danger of inappropriately bamboozling the jury into thinking that such an extrapolation can be anything close to accurate.”
Judge Johnson, concurring (joined by Judge Price), Mata v. State, 46 S.W.3d 902 (Tex. Crim. App. 2001)(opens in new tab)

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What this template gives you that the discipline-specific treatise does not.

01.
Not undated boilerplate: the Widmark-formula limits and the Mata v. State concurrence are source-linked to the opinion, so the citation is one you can verify before you file. Retrograde extrapolation requires data the typical roadside arrest does not produce: time of last drink, food intake, absorption-phase status.
02.
The Widmark r-coefficient varies dramatically across individuals; the prosecution toxicologist routinely picks a single textbook value.
03.
AAFS and peer-reviewed forensic toxicology literature acknowledge retrograde extrapolation is contested when absorption-phase data is missing.

Authorities inside · source-checkable

The controlling authority this template is built on.

Before you buy, see the spine of the deliverable. Verbatim quotes are reproduced word for word from the opinion they cite; any attributed summary is labelled as a summary, never dressed up as a quote. Each entry links to its source so you can confirm it yourself. Nothing is paraphrased into a citation it does not support.

2Controlling authorities cited

2Verbatim opinion quotes

2Checkable source URLs

1Independent source host

Lead controlling authorityVerbatim quote
“The present evidence-based review suggests that the physiological range of ethanol elimination rates from blood is from 10 to 35 mg/100mL/h. In moderate drinkers 15 mg/100mL/h remains a good average value for the population, whereas in apprehended drivers 19 mg/100mL/h is more appropriate, since many of these individuals are binge drinkers or alcoholics.”
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. (PMID 20304569) · Abstract (physiological range 10-35 mg/100mL/h; population average 15)Verify the source
Supporting authorityVerbatim quote
“Widmark estimates for the number of drinks should include a 2CV estimate of approximately 25% while the blood alcohol concentration estimate should include a 2CV estimate of approximately 42%.”
Gullberg RG. Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology. Forensic Sci Int. 2007;172(1):33-39. (PMID 17210238) · AbstractVerify the source

Provenance: every citation above carries a source URL that was fetched and confirmed reachable when the template was authored. A citation without a working source URL does not ship. Counsel of record adapts the motion language to circuit-specific precedent and the facts of the case before filing.

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Daubert, BAC Retrograde, Case details

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Frequently asked questions.

What does the brief contain?

Seven sections: cover (your case identifier + jurisdiction stamped on), reliability standard recap (Daubert v. Merrell Dow factors), the lead authority's verbatim finding with source URL, the cumulative-error history with cited exonerations / IG audits / appellate opinions, recommended FRE 702 motion language (~250 words editable), a 10-15 question cross-examination question bank, and the methods + source URLs bibliography.

Is this legal advice?

No. The template is a research artifact modeled on the published critique literature for this discipline. Counsel of record adapts the motion language to the controlling circuit's FRE 702 doctrine and the facts of the case before filing.

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Do you cite anything I cannot independently verify?

No. Every citation in every brief carries a source URL stored alongside. Lead authorities are PCAST 2016, NAS 2009 / 2014, NRC 1979 / 2003, FBI/DOJ 2015. All are public-domain and linked to their original publication pages.

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