The breath-test result is usually the centerpiece of a New Jersey DWI case. But that result only counts if the police followed a strict set of procedures — and one of the most important, and most frequently broken, is the 20-minute observation period. When officers get it wrong, the entire breath reading can be called into question.
What the rule requires
Before administering the Alcotest, the operator must continuously observe the suspect for at least 20 minutes to ensure they don’t do anything that could contaminate the breath sample — no eating, drinking, smoking, chewing gum, or, critically, burping, belching, regurgitating, or vomiting. The reason is scientific: any of these can bring alcohol from the stomach or mouth up into the breath, producing a falsely high reading known as “mouth alcohol.”
This requirement comes from the New Jersey Supreme Court’s decision in State v. Chun, which set out the detailed conditions under which Alcotest results are admissible. The observation period isn’t a technicality — it’s a foundational requirement for the test to be considered reliable.
Why this matters so much
If the observation period was defective, the defense can challenge the admissibility or reliability of the Alcotest reading. In a case where the breath result is the State’s strongest evidence, weakening or excluding it can change everything. This is the same kind of foundational attack as scrutinizing the Alcotest calibration records — both go to whether the machine’s number can be trusted at all.
Where observation challenges arise
- The officer left the room or was distracted during the 20 minutes.
- The suspect burped, hiccupped, or regurgitated and the clock wasn’t restarted.
- The timeline doesn’t add up — the records show less than a full 20 minutes of actual observation.
- The video — station or booking footage that contradicts the claimed continuous observation.
It fits into a complete DWI defense
The observation rule is one piece of attacking the breath evidence, which sits alongside challenges to the stop, the field sobriety tests, and — where the timing is right — the rising-BAC issue. Each is a way of testing whether the State can actually prove the case.
Charged with a DWI based on a breath test? The procedure matters
Whether the police truly observed you for a continuous 20 minutes is exactly the kind of detail that can make or break a breath reading. If you’re facing a DWI anywhere in New Jersey, it’s worth a free call to have the testing procedure examined closely.
Part of our complete guide: For every related New Jersey offense, claim, and defense in one place, see our NJ DWI Defense Guide.