Read the "Warning Label" of your blood test

When should you trust a blood test result that claims to measures an alcohol concentration?  Start by reading the test's "Warning Label."  Here is an explanation on my legalcoffee blog.

Challenging DUI Breath Testing: The Timing of the Pretest Deprivation Period

Arizona law enforcement often uses breath-testing devices to determine the blood-alcohol concentration (BAC) of a person suspected of DUI.  The Intoxilyzer 8000 is commonly used in Maricopa County.  When a person is suspected of DUI, he is generally requested to blow twice into an Intoxilyzer; this is referred to as “duplicate breath testing.”

The Department of Public Safety (DPS) has issued regulations for duplicate breath testing, which it defines as “two consecutive breath tests that immediately follow a deprivation period, agree within 0.020…of each other...”

In addition, the Department of Public Safety defines a deprivation period as “at least a 15-minute period immediately prior to a duplicate breath test during which period the subject has not ingested any alcoholic beverage or other fluids, eaten, vomited, smoked or placed any foreign object in the mouth.”  Breath-testing experts have stated that the deprivation period is critical to the breath-testing process. (See Kurt Dubowski, “Quality Assurance in Breath-Alcohol Analysis,” Journal of Analytical Toxicology, Vol. 18, October 1994.)
Commonly referred to as “quality assurance” measures, the DPS regulations seek to prevent any factors from affecting the breath sample.  Putting something in the oral cavity prior to the test could certainly change the results. Thus, law enforcement officials must prevent anything being put into a DUI suspect’s mouth prior to the breath tests.

When examining the breath test record, the starting and ending times of the deprivation period must be noted.  A 15-minute time span wherein a person does not put anything in his mouth is not sufficient; the deprivation period must “immediately” precede the first breath test.

The record must not show any gap between the deprivation period and the first breath test. Moreover, the police officer who conducted the deprivation period should be questioned. If he cannot account for any gap in time, then the test fails to comply with DPS regulations and may be inadmissible.