State v. Sliger: “Foreign Substances” in Breath Testing Means Substances Capable of Affecting Reliability; Expert Testimony May Be Required in Debatable Cases

1. Introduction

Case: State v. Sliger, No. 103563-2 (Wash. Aug. 13, 2026).
Court: Supreme Court of Washington (en banc).
Parties: State of Washington (Respondent) v. John Henry Sliger (Petitioner).
Context: Following a fatal collision, Sliger was charged with vehicular homicide. The State sought to admit a jail-administered Draeger breath test indicating an alcohol concentration above the legal limit.

The key issue was foundational admissibility under former RCW 46.61.506(4)(a)(iii) (2020): whether the State presented prima facie evidence that Sliger had no “foreign substances” in his mouth at the beginning of the required 15-minute observation period. Although Sliger denied having anything in his mouth, the officer observed “tiny tobacco strands stuck in teeth” that were not removed before testing.

The dispute required the court to interpret an undefined statutory phrase—“any foreign substances”—in light of the toxicologist’s implementing rule, WAC 448-16-040, which allows the presence of foreign substances to be determined either by mouth examination or by the subject’s denial.

2. Summary of the Opinion

The Supreme Court affirmed admission of the breath test results, but on a narrower and more evidentiary basis than the trial court. The court held that the State satisfied its prima facie burden under former RCW 46.61.506(4)(a)(iii) by offering expert testimony that the observed “tiny strands” of chewing tobacco would not affect the validity (reliability/accuracy) of the Draeger test.

Critically, the court rejected a literal approach under which “any” would mean any quantity of foreign material—an interpretation the court deemed unreasonable because it would yield absurd results and would be inconsistent with the statutory purpose of uniformity and reduced admissibility litigation.

The court added an operational rule: while the State need not present expert testimony in every case, when the presence of a foreign substance is “debatable,” the State establishes a prima facie case only by presenting expert testimony that the substance does not affect reliability.

3. Analysis

3.1. Precedents Cited

Foundational admissibility and reliability focus

  • State v. Baker, 56 Wn.2d 846 (1960): The “seminal” breath-test admissibility case. Baker articulated four foundational requirements, including that the subject had nothing in the mouth and no food/drink within 15 minutes. The court emphasized that if foundational requirements were not satisfied, results were “wholly unreliable.” Sliger uses Baker to ground its interpretive approach in reliability rather than hyper-technical formalism.
  • State v. Keller, 2 Wn.3d 887 (2024): Cited to confirm that Baker established foundational requirements and that the legislature later codified standards in RCW 46.61.506. The concurrence also cites Keller for “strict compliance” language, sharpening the intra-court debate about whether reliability-based interpretation dilutes statutory strictness.
  • State v. Ford, 110 Wn.2d 827 (1988): Quoted for the judiciary’s “ultimate concern” that approved methods yield an “accurate test, competently administered.” Sliger uses Ford (along with Fernandez) to justify reading “foreign substances” as those that can compromise accuracy.
  • State v. Peterson, 100 Wn.2d 788 (1984): Cited for the proposition that challenges to reliability typically go to weight rather than admissibility. This supports the legislature’s 2004 design: once prima facie admissibility is shown, residual disputes are generally for the fact finder.

Interpreting “foreign substance” and avoiding absurdity

  • City of Sunnyside v. Fernandez, 59 Wn. App. 578 (1990): Central to the majority’s interpretive move. Because “foreign substance” was undefined, Fernandez consulted a dictionary definition of “foreign” and then aligned the phrase with the policy of accuracy, reasoning that “foreign substance” should involve substances that “adversely affect the accuracy” of results. Sliger treats Fernandez as strongly persuasive and essentially continuous with the modern statute (despite intervening codification).
  • Fraternal Ord. of Eagles, Tenino Aerie No. 564 v. Grand Aerie of Fraternal Ord. of Eagles, 148 Wn.2d 224 (2002), and State v. Day, 96 Wn.2d 646 (1981): Both support the canon against literal readings producing “unlikely, absurd, or strained consequences,” and the principle that statutory purpose can prevail over “inept wording.” These canons supply the doctrinal basis for rejecting “any means any quantity” where microscopic residue would categorically bar admissibility.

Statutory interpretation framework and standard of review

  • City of Auburn v. Hedlund, 165 Wn.2d 645 (2009): Provides the abuse-of-discretion standard for evidentiary admissibility rulings, while Sliger simultaneously treats statutory/regulatory interpretation as de novo.
  • Alaska Airlines, Inc. v. Dep't of Lab. & Indus., 1 Wn.3d 666 (2023) (quoting In re Impoundment of Chevrolet Truck, 148 Wn.2d 145 (2002)): Cited for the proposition that interpretation of statutes and implementing regulations is a question of law reviewed de novo.
  • State v. J.P., 149 Wn.2d 444 (2003): Frames the interpretive “primary duty” to discern and implement legislative intent.
  • In re Pers. Restraint of Brooks, 197 Wn.2d 94 (2021), and Dep't of Ecology v. Campbell & Gwinn, LLC, 146 Wn.2d 1 (2002): Used for the plain-meaning-first approach and for reading statutory text in context with related enactments.
  • State v. Evergreen Freedom Found., 192 Wn.2d 782 (2019): Cited for ambiguity analysis—if more than one reasonable interpretation exists, the statute is ambiguous and construction is required.
  • In re Adoption of T.A.W., 186 Wn.2d 828 (2016): Supports reading statutory terms consistent with an expressed purpose; invoked to justify tying “foreign substances” to test accuracy/reliability.

2004 statutory scheme: prima facie admissibility and weight vs. admissibility

  • City of Fircrest v. Jensen, 158 Wn.2d 384 (2006), and City of Seattle v. Allison, 148 Wn.2d 75 (2002): Used to describe how the legislature placed an initial prima facie burden on the State, with the defendant retaining the ability to challenge reliability/accuracy after admission.
  • City of Seattle v. Ludvigsen, 162 Wn.2d 660 (2007) (Madsen, J., concurring): Cited to reinforce the legislative intent to reduce admissibility litigation based on “technical or procedural deficiencies” that do not affect accuracy.

Separate opinions’ additional authority

  • The concurrence references RCW 46.20.308(1) (implied consent) and emphasizes strict compliance with former RCW 46.61.506(4)(a)(iii), while still allowing admissibility on a “de minimis” understanding of “any foreign substances.”
  • The dissent cites Rest. Dev., Inc. v. Cananwill, Inc., 150 Wn.2d 674 (2003), for the principle that courts “must not add words” to a statute—arguing the majority effectively created an accuracy-based exception not enacted by the legislature.

3.2. Legal Reasoning

  1. The statutory and regulatory structure: Former RCW 46.61.506(4)(a) makes breath tests admissible if the State produces prima facie evidence of listed conditions, including that the person did not have “any foreign substances” in the mouth at the beginning of the 15-minute observation period (former RCW 46.61.506(4)(a)(iii)). The implementing rule, WAC 448-16-040, allows that determination to be made either by (1) examination of the mouth or (2) the subject’s denial.
  2. Rejecting a quantity-based literalism: The court reasoned that the statute “does not speak to quantity” and that reading “any” to mean “any quantity” would lead to absurd consequences (e.g., microscopic, undetectable residue would defeat admissibility). The court therefore interpreted “any foreign substance” to mean any kind of foreign substance capable of impacting reliability.
  3. Reliability as the interpretive anchor: Drawing from State v. Baker, City of Sunnyside v. Fernandez, and State v. Ford, the court treated reliability/accuracy as the animating purpose of mouth-clearance requirements (i.e., preventing mouth alcohol or contaminants from skewing deep-lung measurements).
  4. Applying the prima facie standard to “debatable” facts: Former RCW 46.61.506(4)(b) directs courts to assume the truth of the State’s evidence and favorable inferences at the admissibility stage. Here, the officer documented visible strands of tobacco. Instead of treating that fact as automatically defeating admissibility, the court held the State carried its prima facie burden by producing expert testimony (Trooper Axtman) that small flecks/strands would not affect test validity, unlike a “lump of tobacco.”
  5. A new evidentiary allocation rule: The court clarified that the State need not call an expert “in every case” where an officer sees nothing or the defendant denies foreign substances. But where presence is “debatable,” the State makes a prima facie case only by presenting an expert to attest the substance does not affect reliability. Reliability disputes remain available to the defense at trial as matters of weight.

3.3. Impact

Practical prosecution burden in contested-mouth cases: The opinion effectively creates a two-track foundational showing under former RCW 46.61.506(4)(a)(iii): (1) routine cases can proceed on denial or examination alone, but (2) cases with visible but arguably insignificant residue may require the State to present expert testimony at the admissibility stage. This is likely to alter motion practice: defense counsel will frame “debatable” foreign-substance facts to trigger the expert requirement; prosecutors will respond by securing breath-test technician testimony earlier (pretrial suppression hearings).

Doctrinal shift in defining “any foreign substances”: The court’s construction ties “foreign substances” to capacity to affect reliability, not to mere physical presence. That narrowing construction reduces categorical exclusion and aligns the admissibility inquiry with the 2004 legislative policy (uniformity and fewer admissibility delays), while still preserving reliability challenges for the fact finder.

Future litigation pressure points: The opinion leaves open what counts as “debatable,” inviting disputes over: residue amounts (food particles, gum, tobacco flecks), visibility, officer documentation, and whether expert testimony must be case-specific or can be generalized. The concurrence’s “de minimis” framing and the dissent’s bright-line textualism also signal that the court may revisit the boundary between strict compliance and reliability-based construction.

4. Complex Concepts Simplified

  • Prima facie evidence (former RCW 46.61.506(4)(b)): enough evidence to support a reasonable inference of the foundational fact—evaluated assuming the State’s evidence is true and viewed favorably to the State at the admissibility stage.
  • 15-minute observation period: a waiting/monitoring period intended to ensure the breath sample reflects deep-lung air (and thus blood alcohol), not “mouth alcohol” from recent substances that can distort readings.
  • “Foreign substance” (as construed here): not every tiny particle; rather, a substance of a type and amount capable of affecting the reliability/accuracy of the breath result (e.g., a “lump” of chewing tobacco versus tiny residual strands).
  • Admissibility vs. weight: “Admissibility” is whether the jury gets to see the breath test at all; “weight” is how persuasive the jury finds it. The 2004 scheme generally pushes many technical disputes into “weight” once the State meets its prima facie burden.

5. Conclusion

State v. Sliger establishes that “any foreign substances” under former RCW 46.61.506(4)(a)(iii) is not a zero-tolerance rule for every trace amount; it refers to foreign substances capable of affecting breath-test reliability. The State satisfied its prima facie showing here through expert testimony that tiny tobacco strands would not affect the Draeger test’s validity. Going forward, the decision’s most significant operational rule is that in “debatable” foreign-substance scenarios, the State may need expert testimony to secure admissibility—while defendants remain free to contest reliability before the jury as a matter of weight.