Legal Update: The Intersection of "Volume Not Met" Breath Samples and Expert Testimony

In the complex world of DUI litigation involving injury or property damage, the scientific reliability of breathalyzer results is often the primary battleground. A recent ruling has shed light on a particularly contentious issue: Can a defendant be found over the legal limit based on breath samples that were flagged as "volume not met"?

The short answer, according to recent judicial findings, is yes—provided the expert testimony meets the rigorous standards of reliability.

The Challenge of "Volume Not Met" Samples

In typical DUI processing, a breathalyzer requires a specific volume of air to ensure it is measuring "deep lung air" (alveolar air), which provides the most accurate correlation to blood alcohol concentration (BAC). When a subject fails to provide the required air volume, the machine flags the result.

Defense counsel often move to exclude this evidence, arguing that these samples are inherently unreliable. However, courts are increasingly denying these motions to exclude, focusing instead on the scientific methodology used by state experts to interpret those results.

Why the Motion to Exclude was Denied

In a recent pivotal case, the court ruled that an expert's opinion based on four "volume not met" samples was admissible. The decision rested on several key pillars:

• Sufficient Facts and Data: Even if a single sample is incomplete, a sequence of multiple samples (in this case, four) can provide a consistent data set that allows an expert to draw a reliable conclusion.

• Reliable Principles and Methods: The expert utilized established toxicological principles to demonstrate that the alcohol concentration in the "volume not met" samples actually underestimates the true BAC.

• Application to Facts: The court found the testimony was not mere speculation but a product of applying known science to the specific digital readouts of the defendant's breath test.

The "Common Law Predicate" vs. Statutory Presumptions

One of the most nuanced aspects of this ruling involves how alcohol evidence is introduced at trial. There are generally two ways to get BAC results into evidence:

1. The Statutory Implied Consent Law: This often carries a "presumption of impairment" if the level is $.08$ or higher.

2. The Common Law Predicate: This requires the prosecution to lay a foundation through expert testimony regarding the test's reliability and the scientific principles behind it.

The Key Takeaway: The court clarified that the admission of blood or breath alcohol evidence under the common law predicate does not automatically trigger the statutory presumption of impairment. While the evidence is admissible to show the defendant had alcohol in their system, the prosecution must still prove actual impairment without the "shortcut" of a legal presumption.

What This Means for DUI Litigation

This ruling reinforces that "technicalities" in breath testing—like insufficient volume—do not lead to an automatic exclusion of evidence. If the prosecution can provide a qualified expert to explain why those numbers are still scientifically relevant, the evidence will likely reach the jury.

For defense teams, this shifts the focus from admissibility (keeping the evidence out) to weight (challenging how much the jury should trust those incomplete samples during cross-examination).