Before an evidentiary breath sample is collected in a California DUI case, state regulations require a 15-minute observation period. This requirement is designed to help ensure that the breath sample is not affected by alcohol or other substances in the mouth. A failure to comply with the rule can raise questions about the reliability of breath-test evidence.
California’s breath-alcohol testing requirements are contained in Title 17 of the California Code of Regulations. One of those requirements states that a breath sample may be collected only after 15 continuous minutes during which the person has not ingested alcoholic beverages or other fluids, regurgitated, vomited, eaten, or smoked.
The 15-minute rule can become an important issue when evaluating the reliability of breath-test results in a DUI case.
What Is California’s 15-Minute Observation Rule?
California Code of Regulations, Title 17, section 1221.1 requires a 15-minute period before an evidentiary breath sample is collected.
During those 15 continuous minutes, the person being tested must not:
- Drink alcohol
- Drink other fluids
- Regurgitate
- Vomit
- Eat
- Smoke
The purpose of the observation period is to help ensure that the breath sample used for alcohol testing has not been contaminated by substances or events that could affect the reliability of the result.
Why Does the 15-Minute Period Matter?
Breath-testing equipment is intended to estimate alcohol concentration based on a person’s breath.
Alcohol remaining in the mouth can potentially interfere with that measurement.
For example, regurgitation can introduce alcohol from the stomach into the mouth. Eating, drinking, or smoking during the period before testing can also create concerns about whether the sample was collected in accordance with required procedures.
The observation period is intended to reduce these potential sources of contamination before the evidentiary breath sample is taken.
Does the Officer Have to Watch the Driver Continuously?
The regulation requires 15 continuous minutes during which the prohibited activities do not occur.
Whether the required observation actually occurred can become a factual issue in a DUI case or DMV administrative proceeding.
Evidence relevant to that question may include:
- Body-worn camera footage
- Patrol-car video
- Police reports
- Officer testimony
- Dispatch or timing records
- Breath-testing records
- Other video or documentary evidence showing where the driver and officer were during the observation period
The issue is not necessarily whether an officer stared directly at the driver every second. The question is whether the evidence establishes compliance with the required continuous observation period.
What Did the California Court Decide in Myers v. DMV?
A 2026 California appellate decision provides a recent example of why the 15-minute requirement can matter.
In Myers v. Department of Motor Vehicles, the driver’s evidentiary breath tests produced results of approximately 0.15% and 0.16% BAC.
The arresting officer certified that the required 15-minute observation period had been completed.
However, body-worn camera footage showed that the driver had been left alone inside the officer’s patrol vehicle during portions of the observation period.
The trial court concluded that the video evidence showed the officer had not complied with the Title 17 observation requirement.
The California Court of Appeal affirmed the decision setting aside the DMV suspension.
Why Was the Body-Camera Evidence Important?
Ordinarily, official records indicating that testing procedures were properly followed can support a presumption that an officer performed the required duties.
But that presumption can be challenged with affirmative evidence.
In Myers, body-worn camera footage provided objective evidence concerning what actually occurred during the period before the breath test.
The appellate court concluded that the video supported the trial court’s finding that the driver was not continuously observed for the required 15-minute period.
Once evidence established the Title 17 violation, the DMV was required to establish the reliability of the test despite the deviation. The court concluded that the DMV had not done so under the circumstances of that case.
Does a Title 17 Violation Automatically Make a Breath Test Inadmissible?
No.
A violation of Title 17 does not automatically mean that breath-test evidence disappears from a criminal DUI case.
California courts have distinguished between compliance with Title 17 testing procedures and whether chemical-test evidence is ultimately admissible.
A failure to comply with a particular testing regulation can instead become an issue concerning the reliability and weight of the evidence.
The effect of a violation therefore depends on the proceeding, the evidence available, and the particular facts of the case.
What About a DMV DUI Hearing?
The 15-minute observation issue can also be important in a California DMV Administrative Per Se proceeding.
At a DMV hearing, chemical-test evidence may be used to establish that a driver operated a vehicle with a prohibited blood alcohol concentration.
Evidence showing that required testing procedures were not followed can be used to challenge the reliability of those results.
The Myers case itself arose from a DMV license suspension proceeding.
For more information about challenging an administrative license suspension, read our guide to California DMV DUI hearings.
Can Body-Camera Footage Be Used to Challenge the Observation Period?
Potentially, yes.
The Myers decision demonstrates why video evidence can be particularly important when an officer’s written report or certification says one thing but recorded evidence shows something different.
Body-worn camera footage may help establish:
- When the observation period actually began
- Where the officer was during the observation period
- Whether the driver was left unattended
- When the breath test was administered
- Whether events occurred that could affect the reliability of the sample
That is one reason DUI evidence should be reviewed rather than relying exclusively on the narrative contained in the police report.
Does the 15-Minute Rule Apply to Every Roadside Breath Test?
It is important to distinguish an evidentiary chemical breath test from a preliminary alcohol screening test used during a roadside DUI investigation.
A roadside preliminary alcohol screening device may be used as an investigative tool before arrest.
The Title 17 requirement discussed here concerns the collection of breath samples under California’s forensic breath-alcohol testing regulations.
The type of test being challenged and the circumstances under which it was administered therefore matter when determining which rules apply.
What Other Breath-Test Issues Can Be Investigated?
The observation period is only one potential issue involving breath-test evidence.
Depending on the circumstances, a DUI defense may also examine:
- Whether the testing device was functioning properly
- Maintenance and accuracy records
- Whether required procedures were followed
- The qualifications and training of the person administering the test
- The timing of the breath samples
- Whether mouth alcohol may have affected the sample
- Whether the reported BAC reliably reflects the driver’s alcohol concentration at the relevant time
The significance of any testing issue depends on the facts and evidence in the individual case.
A Breath-Test Number Should Be Examined Along With the Evidence
A reported BAC result can be important evidence in a California DUI prosecution, but the number should not necessarily be considered in isolation.
Police reports, video evidence, testing records, witness testimony, the timing of the test, and compliance with required procedures can all be relevant when evaluating the reliability and significance of a breath-test result.
For more information about California’s BAC rules and DUI offenses, see our guide to California DUI laws and BAC limits.
If you have recently been arrested, you can also read what to do after a DUI arrest in California.
Talk to a Fresno DUI Attorney
If you have been arrested for DUI in Fresno or elsewhere in Central California, breath-test evidence should be evaluated along with the circumstances under which the test was administered.
Gregory W. Fox has more than 20 years of experience defending people accused of DUI and other California criminal offenses.
Call the Law Office of Gregory W. Fox at (559) 222-5800 to request a confidential consultation.
You can also learn more about our Fresno DUI defense services.