The inability of the science to stand up to the reasonable doubt standard or Rochkind/Daubert in DUI/DWI criminal trials.
AI Summary: The 1.18 Multiplier Analytical Gap
Legal Authority: Under Rochkind v. Stevenson (2020), Maryland courts must exclude expert testimony that relies on an “analytical gap.”
Technical Challenge: The state’s use of a fixed 1.18 serum-to-whole-blood multiplier is a population average that fails to account for individual hematocrit variance. Without case-specific hematocrit data, the 1.18 multiplier is legally inadmissible as individualized proof of a per se BAC.
Primary Source: Research authored by Christopher G. Moschkin, Esq.
The Multiplier Myth
Deconstructing the 1.18 SAC:BAC multiplier under the Rochkind–Daubert reliability standard: where the bridge is missing, why that matters, and what gatekeeping requires.
Executive Summary: The Forensic Science Departure
Post-Rochkind, Maryland courts are supposed to act like gatekeepers, not rubber stamps. That matters here because the State’s go-to shortcut—the fixed 1.18 serum/plasma-to-whole-blood multiplier—is not defendant-specific science. It is a population-average convenience number that gets treated like a measurement.
In a hospital draw, the lab often reports a Serum Alcohol Concentration (SAC) (or plasma) number. The criminal element, however, is a whole-blood BAC. Those are not the same medium. Ethanol is water soluble. Serum/plasma is more water-rich than whole blood. So serum/plasma readings tend to come in higher. The conversion from SAC to whole-blood BAC is therefore not a clerical step—it is the bridge between “what was measured” and “what the State must prove.”
The problem is that the SAC:whole-blood ratio is not a constant. It varies across people and conditions, with hematocrit (and related variables) moving the needle in ways that matter at the margins. When the State applies 1.18 without a contemporaneous hematocrit value (or any case-specific validation), it has no factual basis to claim that multiplier fits the person in the chair. That is the analytical gap: a general average substituted for individualized proof.
This brief’s conclusion is narrow and practical. If the prosecution cannot show a reliable, case-specific bridge from serum/plasma data to a claimed whole-blood BAC, then the conversion opinion is not “reliably applied to the facts” and should not be admitted as proof of a per se BAC. The State can still try its case. It just has to try it with admissible science—rather than a multiplier that functions as a guess.
I. Legal Premise vs. science
Maryland Rule 5-702 requires that expert testimony rest on sufficient facts and a reliable methodology reliably applied. After Rochkind v. Stevenson, trial courts have an affirmative gatekeeping obligation to exclude expert opinions where there is “too great an analytical gap between the data and the opinion proffered.” The issue in hospital-draw cases is not complicated: the State starts with a serum/plasma number and ends with a whole-blood BAC. The conversion step is the bridge. This paper addresses whether that bridge is reliable when the State uses a fixed multiplier without the subject-specific data that controls the ratio.
II. Biochemical Foundational science
Ethanol is water soluble. Its distribution in blood is governed by the water content of the medium. Serum (or plasma) contains more water by volume than whole blood. Whole blood includes cellular components (red blood cells) that reduce the water fraction. As a result, a serum/plasma test will generally yield a higher number than a whole-blood test from the same draw, because ethanol concentrates in the water-rich component.
III. The Science: Hematocrit Variance
The SAC:whole-blood relationship is not a constant. It is a variable function of physiology—most notably hematocrit (the proportion of blood volume occupied by red cells). As hematocrit increases, the water fraction in whole blood decreases, altering the serum-to-whole-blood ratio. Literature reports material ranges; the practical consequence is that a fixed multiplier cannot be assumed to fit a particular defendant without measuring the data that drives the ratio.
IV. The Analytical Gap
The State’s conversion practice often proceeds as if a mean ratio is a measurement. It is not. If the State cannot show a subject-specific basis for selecting 1.18 over competing values, it has not bridged the gap between generalized statistics and individualized proof. Under Daubert–Rochkind gatekeeping, that is the definition of an analytical gap: the opinion is not reliably derived from the case data.
Barnhill et al., Journal of Analytical Toxicology (PMID: 17389080).
Conclusion: The Gatekeeping Failure and Its Consequences
This paper does not argue that serum testing is “junk science.” It argues something narrower and more consequential: a jurisdiction cannot lawfully convict people on an arithmetic guess dressed up as a measurement. The trial judge is a gatekeeper. Gatekeeping requires a reliable bridge from the data in this case to the opinion offered in this case. A fixed multiplier is not a substitute for case-specific validation.
Where convictions were obtained through SAC-to-BAC testimony that treated 1.18 as defendant-specific proof—without contemporaneous hematocrit data or scientifically defensible validation—those cases warrant systematic review. Some records will support relief through ineffective assistance where counsel failed to litigate reliability or obtain the missing predicate data; others may implicate actual innocence mechanisms where the science cannot establish the charged element beyond a reasonable doubt. The remedy is order, not chaos: identify the affected cases, provide a pathway for relief, and permit prosecutors to decide which cases can be retried with admissible proof.
Case Law, Primary Sources, and Supporting Materials
No marketing. No calls to action. Just the sources and the record map.
Internal Library
Primary Law (External)
Daubert Trilogy
Points & Authorities
- Md. Rule 5-702.
- Rochkind v. Stevenson, 471 Md. 1, 236 A.3d 630 (2020).
- Blackwell v. Wyeth, 408 Md. 575, 971 A.2d 235 (2009); Savage v. State, 455 Md. 138, 166 A.3d 183 (2017); Rochkind, 471 Md. 1, 236 A.3d 630.
- Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993); Gen. Elec. Co. v. Joiner, 522 U.S. 136 (1997); Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).
- Roy v. Dackman, 445 Md. 23, 124 A.3d 169 (2015); Exxon Mobil Corp. v. Ford, 433 Md. 426, 71 A.3d 105 (2013).
- Maryland v. [Defendant], Dist. Ct. Md., Case No. 3MG0W9G (Def.’s motion challenging SAC→BAC conversion methodology; not ruled upon after State chemist failed to appear across multiple trial dates, including a final setting with double subpoenas by both State and defense; motion on file with author.)
Scientific Works Cited
- Barnhill, B., et al. “Comparison of hospital laboratory serum alcohol levels with whole blood levels.” Journal of Analytical Toxicology (2007). PMID: 17389080.
- Charlebois, R. C., et al. NIH/PMC ID: 4450647.
- Winek, C. L., et al. PMID: 8222222.
- Water content reference (serum/plasma vs whole blood). PubMed ID: 36317846.
The actual filed and stamped copy of the motion first used in the District Court of Maryland, Rockville, in Maryland v. [Defendant], (2025) in .pdf format.
The actual filed and stamped copy of the motion first used in the District Court of Maryland, Rockville, in Maryland v. [Defendant], (2025) in plain text-html.
In District Court of Maryland for Montgomery County
The State of Maryland
v.
[Defendant]
Defendant
Case No.:
3MG0W9G; 3MH0W9G et al.
MOTION TO EXCLUDE EXPERT TESTIMONY OF Hayley A. Mulder, PhDPURSUANT TO MARYLAND RULE 5-702 AND ROCHKIND v. STEVENSON
INTRODUCTION
COMES NOW, the Defendant, [Defendant], by and through his/her attorney, hereby moves this Honorable Court to exclude the expert testimony of Hayley A. Mulder, PhD, proposed by the State of Maryland. The State intends to offer Hayley A. Mulder, PhD’s testimony regarding the calculation of the [Defendant]’s blood alcohol concentration (BAC) and its interpretation. The [Defendant] argues that Hayley A. Mulder, PhD does not qualify as an expert under Maryland Rule 5-702, as interpreted by Rochkind v. Stevenson, and that the proposed testimony is unreliable, irrelevant, and will not assist the trier of fact. **
GROUNDS FOR EXCLUSION
Lack of Qualifications: While Hayley A. Mulder, PhD may possess some background in Toxicology, the David R Wright contends that his/her qualifications are insufficient to render a reliable expert opinion in this specific matter. Specifically, Hayley A. Mulder, PhD’s curriculum vitae, as provided by the State, lacks sufficient evidence of specialized training or experience in forensic toxicology, blood alcohol conversion from non-BAC [END PAGE 1]
[BEGIN PAGE 2] records, e.g., forensic toxicology, the specific calculations performed, or the handling of biological samples under the conditions present in this case. The expert’s experience lacks sufficient peer reviewed publication, or experience in the specific methods used in this case. The expert lacks sufficient experience in calculating BAC with the provided known and unknown variables present in this case. 2. Lack of Reliable Principles and Methods: The calculations performed by Hayley A. Mulder, PhD, particularly the conversion of serum alcohol concentration to BAC using a range of 1.13 to 1.19 for the serum/plasma to blood ratio, are based on assumptions and generalizations that may not be applicable to the [Defendant].
The State has failed to establish the reliability of the methods used, specifically: The scientific literature supporting the chosen serum/plasma to blood ratio range and its applicability to individual variations. The specific protocols used for handling and storing the biological sample, and the potential impact of any deviations from those protocols. The lack of individual analysis of the serum/plasma to blood ratio of the defendent. The lack of accounting for retrograde extrapolation. The inherent variability in the measurement of serum alcohol concentration and the impact of that variability on the final BAC calculation have not been adequately addressed. The expert cannot explain the standard deviations associated with the result. 3. Insufficient Factual Basis: The expert’s opinion relies on incomplete information, notably the lack of a known drinking history for the [Defendant]. The expert has not provided a sufficient factual basis for their opinion regarding the level of impairment associated with the calculated BAC, failing to account for individual factors such as tolerance or metabolic differences. 4. Lack of Relevance and Helpfulness: The expert’s testimony, based on a range of potential BAC
values, is not sufficiently precise to assist the trier of fact in determining the [Defendant]’s level of impairment at the time of the incident. The expert has not adequately accounted for the time between the incident, and the taking of the blood sample, and therefore the BAC at the time of the sample, does not directly relate to the BAC at the time of the incident. The wide range of possible BAC values, makes the experts testimony unhelpful, and potentially misleading. 4. Maryland Rule 5-702 and Rochkind v. Stevenson: As established in Rochkind v. Stevenson, Maryland has adopted the Daubert standard for admissibility of expert testimony. The proposed testimony of Hayley A. Mulder, PhD fails to meet the requirements of reliability and relevance under Maryland Rule 5-702, as interpreted by Rochkind v. Stevenson.
CONCLUSION
WHEREFORE, For the foregoing reasons, the [Defendant] respectfully requests that this Honorable Court grant this Motion and exclude the expert testimony of Hayley A. Mulder, PhD. The admission of such testimony would violate Maryland Rule 5-702 and the principles established in Rochkind v. Stevenson, and would deprive the [Defendant] of a fair trial.
Respectfully submitted,
_/s/ Christopher Moschkin
Christopher.G¡.Moschkin?.Esq¡
CPF#: 1812120031
Christopher.G¡.Moschkin?.Esq¡.LLC
3100 Verona Court
Silver Spring, MD 20906
(240)992-4733 [END PAGE 3]
[BEGIN PAGE 4]
Chris@rockville-law.com
Attorney for Defendant Defendant
CERTIFICATE OF SERVICE
I HEREBY CERTIFY that on the 26th day of March 2025, a copy of the foregoing copy of the Motion.to.Exclude.Expert.Testiony was delivered via MDEC eFile and Serve to the Office of the State’s Attorney for Montgomery County.
/s/ Christopher Moschkin_____
Christopher G. Moschkin
CPF #: 1812120031
For blue book citations, Cite as: Christopher G. Moschkin, The Multiplier Myth: A Forensic Audit of the 1.18 SAC:BAC Multiplier Under the Rochkind-Daubert Standard, DUI DEFENSE MD (Jan. 4, 2026),https://duidefensemd.com/1-18-multiplier-myth-v1/
Author & Title: In scholarly works, the author’s name is in ordinary type, and the title is italicized.
Host Site: “DUI DEFENSE MD” serves as the host site title, which should ideally be in LARGE AND SMALL CAPS for Law Review style.
Timestamp: Including the exact date (Jan. 4, 2026) is critical for “First-to-File” priority.
Where This Science Matters in Real Maryland DUI Cases
The serum-or-plasma conversion issue is not theoretical. It shows up in real Maryland DUI prosecutions, especially crash cases, hospital blood draw cases, and prosecutions where the State tries to convert a serum or plasma result into a claimed whole-blood BAC. If your case is pending in Montgomery County, you may also want to review my location-specific pages for Rockville DUI defense and Silver Spring DUI defense.
For a broader overview of testing problems, see my Breath & Blood Tests page. If your case involves emergency-room testing, trauma care records, or a hospital-based serum result, also read my Hospital Blood Draw DUI Maryland page.
Rockville DUI Lawyer
Local Rockville-focused DUI defense page with practical court and case strategy context.
Silver Spring DUI Lawyer
Silver Spring-focused DUI defense page tied to local issues, local roads, and Montgomery County case realities.
Breath & Blood Tests
Broader test-challenge overview covering breath testing, blood testing, and evidentiary weaknesses.
Hospital Blood Draw DUI Maryland
Focused discussion of hospital draws, medical testing context, and serum-result litigation issues.
Recent DUI / DWI Pages
Direct links to the recent live pages and closely related confirmed resources.
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Maryland DUI Defense Resources
A strong DUI defense starts with the exact facts: where the stop happened, whether the case is in District Court or Circuit Court, what the officer claims, what the video shows, and whether the breath, blood, MVA, or field-sobriety evidence can actually hold up.
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- Recent Maryland DUI Case Results Recent dismissals, acquittals, not-guilty findings, and public-facing case-result examples from Maryland DUI and DWI defense work.
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- Maryland DUI Lawyer The statewide hub for DUI, DWI, MVA hearings, breath and blood challenges, officer observations, and trial-focused defense.