The Importance of a 15-20 Minute Continuous Observation Period Just Prior to Breath Testing

California DUI lawyers often call this the big-ticket issue in California DUI breath test cases.

California's 15 minute alcohol deprivation / continuous observation period is a universal DUI requirement:
Established scientific safeguards (e.g., a 15-minute pretest “deprivation period” and use of control tests) are necessary to assure the validity and the legal admissibility and acceptability of the results of breath-alcohol analysis when carried out for forensic purposes.
[Dubowski, K.M., The Technology of Breath-Alcohol Analysis, DHHS Publication, No. (ADM) 92-1728, 1991 (printed 1992), p. 1.]
When breath test results are intended for quantitative evidential purposes, the measurements must not be made less than 15-20 minutes after the subject has finished drinking. This time delay is necessary to allow for dispersion of high concentrations of alcohol mixed with saliva and mucous secretions in the mouth.
[Physiological Aspects of Breath Alcohol Measurement, p. 15.]

California DUI attorneys regularly inquire into this fundamental requirement that the officer continuously observe the subject for at least 15 minutes just prior to actual breath testing.
California DUI police officers often check boxes or sign pre-printed forms that they perform this, but often they actually fail to do so properly.

Some California DUI machine operating manuals include the following warning on mouth alcohol issues:
The mucous lining of the mouth cavity and nasal passages stores alcohol for some time after a person consumes alcohol. Normal body processes eliminate residual mouth alcohol within 15 minutes. Therefore, observe a subject for at least 15 minutes before performing a test. During the observation time, the subject may not eat, drink, or introduce any substance into his mouth. Furthermore, if the subject regurgitates, note the time and delay starting a breath test for at least 15 minutes.
[CMI, Inc., Basic Maintenance and Repair of the Intoxilyzer 5000 Breath Analysis Instrument, 10/1/84, p. 44.]

In one study, 30 subjects either rinsed their mouth (and expectorated) with 10 mL of 20% w/v gin, or consumed the gin. Breath samples were obtained with an Intoxilyzer® 5000 at 5 and 10 minutes after alcohol administration. The mean Intoxilyzer® results ranged from 0.091+/-0.051 to 0.036+/-0.027 five minutes after administration to 0.014+/-0.011 to 0.004+/-0.006 g/210 L ten minutes after administration. Most interestingly, the mouth alcohol was not correctly identified by the Intoxilyzer all the time. The percentages of times that mouth alcohol was correctly detected by the Intoxilyzer® 5000 were 90% to 66%(swallowing) after 5 minutes and 62% to 30%(swallowing) after 10 minutes. Even after ten minutes, 63% of the Intoxilyzer® results were > 0.010 g/210L after rinsing (7% after swallowing). [Wigmore, J.G., Leslie, G.M., The Effect of Swallowing or Rinsing Alcohol Solution on the Mouth Alcohol Effect and Slope Detection of the Intoxilyzer 5000, J Anal Toxicol, 2001, Mar; 25(2):112-114.]

When a California DUI lawyer shows that an officer failed to observe this Title 17 requirement, DMV is required to give the driver his or her license back.

When a California DUI attorney demonstrates an officer failed to continuously observe a subject during the 15 minutes just prior to testing, that is something a jury can take into consideration in determining whether the test is reliable or trustworthy in a criminal California DUI case.