Blood Tests: There are many defenses that can be utilized to challenge blood alcohol results. Blood tests are typically more accurate than breath tests; thus, they are usually challenged less often. First, when a laboratory tests the blood sample for blood alcohol content, it usually employs a method called headspace gas chromatograph. Headspace is considered the gas in the vial between the sample and the top of the vial. A sample of that gas is taken and placed into the gas chromatograph (GC). The GC tests the sample and determines the blood alcohol content. It is assumed there is a generalized ratio between alcohol content in the blood and alcohol content in the headspace. That ratio is utilized to determine the person’s blood alcohol content. Defendants have a right to a blood split in which the blood sample may be retested. When the blood sample is retested the toxicologist typically utilizes direct injection. Direct injection is when a toxicologist will take a sample of the blood and directly insert it into the chromatograph. It is important to contact a skilled DUI defense attorney to subpoena the laboratory’s testing practices, methods, and technician notes to aid in your defense.
Breath Tests: First, a skilled DUI attorney should subpoena all accuracy checks, maintenance and calibration records for the particular breath testing device. Second, depending on the results, the attorney may consult with a toxicologist to review any additional attack methods. Third, all breath testing devices have a margin of error plus or minus .01% meaning, a blood alcohol content of 0.08% could be as low as a .07% or as high as a 0.09%. Fourth, a breath testing instrument is unable to actually measure the alcohol content in the blood, rather it measures the alcohol content in breath particles and converts it to reflect a blood alcohol content. It is assumed that there is a 2100:1 ratio when converting breath alcohol to blood alcohol. Meaning the concentration of alcohol in a person’s blood is 2100 times the alcohol in a person’s breath. This is known as a partition ratio. The 2100:1 ratio is a generalization and would vary between individuals. Finally, there are a number of additional ways to challenge the results of a breath test. You should contact the Parker Law Center to explore your defense.