A Presumption of Reliability exists when it comes to San Diego DUI breath test results at license hearings at California DMV.
As soon as your San Diego DUI defense attorney presents evidence of a failure to follow any standard (e.g. the fifteen minute continuous observation standard), the DMV lawyer has rebutted the presumption. The burden of proof shifts over to California DMV to somehow try to prove reliability of the BAC reading. See this Article, the DMV manual and the relevant case law.
When DMV does not meet that burden, DMV does not suspend the driving privilege of the San Diego DUI arrestee.
The key case is Manriquez v. Gourley. One reasonable review of that decision is as follows:
To show a proper fifteen minute continuous observation period prior to any San Diego breath test upon a DUI or drunk driving arrest:
(A) The San Diego area DUI cop has to remain in the presence of the breath test subject for the fifteen minutes before blowing, and
(B) The San Diego DUI cop has to – via use of all senses [Sight, Smell, and Sound] – be able to ensure the breath test subject has NOT ingested alcoholic beverages or other fluids, regurgitated, vomited, eaten, or smoked, or suffered physical symptoms (e.g. burped, belched or regurgitated gas). If cop fails to ensure, BAC reading is unreliable because it could be falsely elevated or otherwise adversely affected.