Relationship between amount of alcohol in blood and breath for DUI investigation in Los Angeles.

June 27, 2013

A true measure of alcohol in a person’s body is done by analyzing the blood.  However, most Los Angeles DUI cases do not involve blood analysis.  Insead, most persons arrested for DUI in Los Angeles provide a breath sample.  To convert breath sample to a blood alcohol level, a machine (such as EC/IR, or a DamaMaster DMT) will determine number of alcohol particles in a person’s breath sample and multiply it by 2100.  Thus, it is assumed that 2100 cubic centimeters of breath will contain the same amount of alcohol as 1 cubic centimer of blood.  This is based on legal assumption that all person have the same conversion ration between breath and blood concentration of alcohol regardless of age, body structure or sex has the same ratio of alcohol in the blood to breath.

This assumption is based on a Henry’s law which states that in a “closed system” concentration of alcohol in liquid is directly related to concentratino of alcohol in vapor above the liquid. The problem is not that Henry law is invalid but that a human body is a not a “closed system”.

In scientific literature this ratio is called the “partition ratio” and in the United States it is universally accepted by law enforcement crime labs as 1:2100.  This of course is ridiculous and is based on some questionable scientific articles.  One such questionable scientific article is a study by Dena Jaffe conducted in Israel with a conclusion that blood alcohol and breath alcohol results are highly correlated – having a correlation ratio (r) of 0.984.  Close look at the paper reveals the ratio of blood to breath alcohol level to be as low as 2000:1 and as high as 2500:1 and went to a low of 1214:1 to high of 2859:1.  This is a 20 percent difference depending on person in study and 260% increase from low to high.  The study decided to use mean as a way to measure correlation.  But does not it sound ridiculous to use “mean” for dozens of individuals to justify a conviction?   Mean is like an average and averaging the “partition ratio” is as cool as averaging weight or height.  The partition ratio between people vary just like the height does.  It is no more fair to prosecute based on low breath test results that it is to assume that all defendants are of average height of  5 ft 10 inches.  The truth is, some people are 6 feet tall and some are 5 feet tall – some people’s ratio is 1500:1 and some are 2600:1.  The difference in partition ration will be very pronounced at some people and cause a true blood alcohol level below 0.08 percent – especially with low breath blood alcohol levels.  If you are fighting DUI and your blood alcohol level is relatively low, your breath tests might be inaccurate if your partition ratio is not the average used by law enforcement.  If that is the case – call us now.  We specilize in defending all types of DUI cases and have great success sotries to share including dismissals of DUI cases.  Contact us at (877) 940-4440 or (323) 464-6424.

FYI: the studies that were basis for this ridiculous partition ratio are from the 1970th and 1980th.  This conversion ratio is an average for many individuals and not only it can vary from person to person to as low as 1300:1 to as high as 2700:1; but, it can also vary within one person.  The reason ratio changes within person because in the initial stage of alcohol consumption more alcohol is present in arterial blood and less in venous blood.  Because blood that is drawn for testing is drawn from veins, the ratio will be lower initially and higher later.  Also, climate and even the type of machine used will affect the conversion ratio.  Even the type of machine used to measure blood alcohol level can cause a variance.  One study compared Intoxilyzer 5000 and the Seres Ethyulometre infrared analyzer and found a 19-26% variance between two machines.   This is just one more example of unfairness of DUI prosecutions.

Call Los Angeles DUI attorney to defend your Los Angeles DUI case.  We can provide quality affordable representation for your drunk driving case in Los Angeles.

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