Test Assumptions in Blood Alcohol Breath Testing and How to Use Them to Our Advantage.

Orange County DUI Lawyer

Test Assumptions in Blood Alcohol Breath Testing and How to Use Them to Our Advantage.

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Many times the state will state that a person is under influence at a .05 or higher.  They do this all the time.  This is insurance for them if they lose the B count which says that you were over .08 at the time of driving. However, this is also a double edge sword for them. This is so especially in breath cases because it opens the door to a partition ratio argument.

Blood alcohol tests assume the individual being tested is actually normal. . For example,  the ratio of blood alcohol content to breath alcohol content (the partition ratio) is 2100 to 1. It is necessary to assume , there are 2100 parts of alcohol in the blood for every part in the breath. However, the actual ratio in any given individual can fluctuate from 1300:1 to 3100:1, or even more widely. This ratio does not change  from person to person, but within one person from moment to moment!!! . Therefore a person with a true blood alcohol levels of .08% but a partition ratio of 1700:1 at the occasion of testing would have a .10 reading on a Breathalyzer calibrated for the average 2100:1 ratio. A similar assumption is made in urinalysis. Whenever urine is analyzed for alcohol, the assumption is that there are 1.3 parts of alcohol in the urine for every 1 role in the blood, likewise though the actual ratio can differ greatly.

Breath alcohol testing further assumes that the test is post-absorptive“”that is, that the absorption of alcohol in the subject’s body is complete. If the topic is even actively absorbing alcohol, their body has not reached a state of balance in which the focus of alcohol is uniform throughout the body. Many forensic alcohol specialists reject test outcome during this period as the quantities of alcohol in the breath will not accurately reflect a true focus in the blood.

For reason to much to discuss here. The partition ratio can only used in the A count and not the B count as it is built into the charge.  (driving on an .08 or more based on a partition ratio of 2100) The partition ratio argument can only be used as a defense to the A count. However, the science is murky especilly to jurors who are hearing this the whole time. They will only hear a partition ratio conversion followed by a much lower number. This can be used for the benefit of the defense.


Hieu Vu

Hieu Vu

Hieu Vu is an attorney out of Southern California practicing mainly in DUI. He demonstrates advanced knowledge of procedure and case law. His commitment to his clients is unparalleled. His tenacity and victories in trial are already earning him the respect of his peers outstanding and dedicated DUI trial lawyer who really cares about his clients. Hieu is also very knowledgeable about the law and the science relevant to DUI defense and is a very passionate and aggressive criminal defense attorney practicing in Orange County and Los Angeles County courts. He is extremely motivated for his clients and is an excellent advocate and excels in the courtroom. Hieu Vu can be contacted for a consultation at 714-251-6567.

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