Generally, it takes about 10-12 minutes for mouth alcohol to dissipate and not effect the test. However, if a person has belched within about 10 minutes of the test, the mouth alcohol will falsely contribute between .01 and .03 to the result. The breath test operator protocols require the officer to "be in the presence of" (but not observe) the DWI suspect for 15 minutes to assure they don't belch or place foreign objects into their mouth effecting the test. As a practical matter, though, the officer is rarely paying much attention to whether the suspect is burping or belching. They are typically busy filling out paperwork, driving the suspect to the police station, talking with other officers, or getting the Intoxilyzer warmed-up for the test. If a person burps silently there's no way the officer is going to detect it.
The Intoxilyzer 5000 does attempt to detect mouth alcohol by what is called the "slope detector." The slope detector is a computer program designed to measure the rate at which alcohol concentration changes inside the Intoxilyzer 5000. If the concentration changes too fast (i.e., too "steep" of a slope), the machine registers an alert and the test is aborted. The slope detector must be “satisfied” before the Intoxilyzer 5000 will produce a result. The problem is that empirical studies show the slope detector does not always work as advertised. Moreover, Texas does not have a standard procedure approved for use by the technical supervisors to verify the slope detector feature of the Intoxilyzer 5000 is working properly and conforms to the manufacturer's certification.
At trial the technical supervisor will generally testify: (1) they don't know what process was followed in developing the slope detector program; (2) they don't know of any treatises or literature that support the use of the process followed to develop the program; (3) they don't know whether the program has been published or offered for publication in any peer-reviewed journal; (4) they don't know whether the program been described in any peer-reviewed journal; (5) they don't know whether any other scientists use or recommend use of the program; (6) they don't know whether there's a known or potential rate of error; and (7) they don't know whether there are any studies showing the slope detector actually works as advertised.
The next installment in this series will discuss the 2100:1 Blood:Breath Partition Ratio and more on Henry's Law. Call a good Bryan-College Station DWI defense attorney for help!