A 4-1-4 Split and a Straw Man: Why State v. Sliger Leaves Washington’s Breath-Test More Confused Than Before
On August 13, 2026, the Washington Supreme Court decided State v. Sliger, No. 103563-2. The case started with tobacco strands in a defendant’s teeth and ended with the Court affirming a vehicular homicide breath test’s admissibility. On its face, that sounds like a resolved question. Look at the vote count though, and its anything but resolved.
The Vote: 4-1-4, and No Majority Rationale
Nine justices at on this case (including two justices pro tempore, Madsen and Yu). Here’s how they broke down:
Madsen’s Lead Opinion. Joined by Chief Justice Stephens and Justices Johnson and Whitener (4 votes). This opinion holds that “any foreign substance” means any substance capable of affecting the reliability of the test, and that in “debatable” cases the State must produce expert testimony that the substance in question doesn’t compromise reliability.
Gonzalez’s Concurrence in Result Only. Justice Gonzalez agrees the test results are admissible, but rejects the lead opinion’s reliability-and-expert-testimony framework entirely. In his view, “any foreign substance” simply means anything more than a de minimis quantity, and a defendant’s denial alone is enough to create a reasonable inference that no more than a de minimis amount was present. No expert needed.
Mungia’s Dissent. Joined by Justices McCloud, Montoya-Lewis, and Justice pro tempore Yu (4 votes). The dissent would suppress the test results outright on the theory that the statute means what it says any foreign substance, full stop.
Add it up. 5 justices vote to affirm the judgment, but only 4 of them agree on why. That’s the classic structure of a plurality opinion, and it matters enormously for what this case is actually worth going forward.
Why This Matters for Precedent
Washington has a specific rule for reading fractured opinions like this, and its not “the four-justice opinion wins because it has the most signatures.” Under Davison v. Hensen, 135 Wn. 2d 112, 128 (1998): “Where there is no majority agreement as to the rationale for a decision, the holding of the court is the position taken by those concurring on the narrowest grounds.”
Applied mechanically, that points towards Gonzalez’s one-justice concurrence, not Madsen’s four-justice “lead” opinion, as the actual binding rule because his tests: (1) “Any foreign substance” = anything more than a de minimis quantity; or (2) a denial alone satisfies the State’s burden, no expert required, asks for less than Madsen’s does to reach the same result. The “lead opinion” label is doing more rhetorical work than legal work here.
But there’s a deeper problem. The narrowest-grounds rule only works when the competing rationales are nested, on a true logical subset of the other. Madsen’s and Gonzalez’s aren’t. They’re independent tests keyed to different facts (a denial, versus substance-specific expert testimony), and a future case could satisfy neither. When rationales fork like that instead of nesting, court's applying this doctrine have held no synthetic holding can honestly be extracted, the decision binds the judgment, but controls nothing else. So there are two live possibilities following Sliger, and both are bad news for anyone looking for a rule. Either Gonzalez’s concurrence quietly controls instead of the opinion everyone will most certainly cite as the “lead” or no opinion controls at all.
That’s the real headline of this case, and its buried under the “we affirm” language at the top. The substantive question of what “any foreign substance” means under RCW 46.61.506 remains legally unsettled in Washington, even though the specific defendant lost. The Courts of Appeals, prosecutors, and defense counsel are now stuck reading tea leaves across two opinions that agree on the outcome and disagree on the law.
The Statutory Construction Problem: The “Microscopic Substance” Argument is a Straw Man
Set the vote count aside for a moment and look at how the lead opinion gets to its reliability test in the first place. The move is worth scrutinizing closely, because it’s the load-bearing wall of the entire opinion—and it doesn’t hold up.
The lead opinion’s core argument against reading “any” literally is this: if “any foreign substance” really meant any quantity at all, then “the presence of microscopic amounts of a foreign substance would prevent the admissibility of breath test results,” and “officers are not equipped to conduct a thorough inspection of an individual’s mouth for any strand or speck of a foreign substance.” That absurdity, the lead opinion says, justifies reading in a reliability requirement that isn’t in the statutory text.
Mungia’s dissent calls this out directly, and correctly: nobody was arguing for a microscopic substance standard. The implementing regulation, WAC 448-16-040(1), already answers the detection-method question. An officer determines whether a foreign substance is present by either a visual examination of the mouth or the subject’s denial. A visual exam with the naked eye cannot, by definition, turn up microscopic debris. The regulation caps the practical scope of “any” long before you ever get to the word’s plain meaning. So the lead opinion’s hypothetical about undetectable specks derailing every breath test in the state as never actually on the table; instead, its a straw man built to make the literal reading of the statute unworkable, when in fact the literal reading was never being pushed to that extreme by anyone in the case.
Once you strip out the microscopic-substance hypothetical, what’s left is the actual, undisputed fact patter. An officer saw tobacco strands with his own eyes, wrote it down in his report, and testified about it under questioning. This isn’t a case about invisible contamination; it’s a case about visible debris that the statute’s plain text, on its own terms, doesn’t distinguish by size. The lead opinion needed the microscopic hypothetical to make “any” seem unreasonable; without it, ““any” just means any.
There’s a second textual problem the lead opinion glosses over. The statute doesn’t just say “any foreign substance.” It says “any foreign substances, not to include dental work or piercings, fixed or removable.” The legislature already knew how to write exceptions into this list and did so for exactly two categories. Under the ordinary interpretive principle that courts shouldn’t add exceptions the legislature chose not to write, the presence of two explicit carve-outs is strong evidence the legislature meant “any” to be read broadly everywhere else. The lead opinion’s judicially-created “unless it doesn’t affect reliability” exception isn’t the kind of gap-filling that’s appropriate when the legislature has shown it drafts its own exceptions.
Finally, the lead opinion’s reliability test cuts against the statute’s internal structure. The legislature was explicit that admissibility challenges and reliability/accuracy challenges are different questions assigned to different decision-makers. Admissibility is a question assigned to the trial court. Reliability/accuracy are questions for the jury, at trial, and as to weight. By requiring expert testimony about reliability at the admissibility stage whenever a foreign substance’s presence is “debatable,” the lead opinion imports a jury-type reliability inquiry into what the legislature designed as a fast, bright-line gatekeeping step. That’s precisely the sequencing the legislature said it didn’t want and its worth remembering why. The 2004 codification was passed to speed up DUI prosecution and cut down on exactly this kind of technical wrangling at the admissibility stage.
The Dissent Has the Better of This Argument
Mungia’s dissent is not just an emotionally appealing “you can’t add words to a statute” position. It’s the more textually and structurally disciplined reading. The statute says “any.” It explicitly enumerates two exceptions to “any.” The implementing regulation already limits detection to a naked-eye visual exam or the subject’s denial, which forecloses the lead opinion’s fear of a microscopic-debris standard before that fear is even relevant. And the legislature separately, explicitly walled off reliability and accuracy questions to be decided by the jury at weight—not smuggled into the admissibility threshold by expert testimony requirements the statute never mentions.
None of this means the policy outcome is heartless. The dissent doesn’t dispute that DUI prosecutions matter or that a few flecks of tobacco seem trivial compared to a fatal collision. What it insists on is that the legislature, not the court, gets to decide where that line is drawn. And, the legislature already drew it, in the word “any” and in the two exceptions in chose to write.
The Bottom Line
State v. Sliger, affirms one conviction. It does not settle Washington law. With four justices behind a reliability-and-expert-testimony test, four justices in dissent insisting on a literal reading, and one justice concurring in the result on an entirely third theory, the next Washington trial court facing a “was there a foreign substance in the mouth” dispute has no majority opinion to follow. Only three competing views split 4-1-4, once of which (the dissent’s) actually tracks what the statute says. Until the legislature clarifies the text or a future case manages to produce an actual majority, expect this fight to keep recurring, one breath test at a time.
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