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(619) 326-8161
The Law Office of


(619) 326-8161
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Judge's Assistant and Deputy District Attorney
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Breath and Blood Testing


DUI for Adults

To secure a conviction for DUI (driving under the influence) in San Diego, law enforcement and the prosecuting attorney will often utilize a driver’s breath or blood test results. A breath test, blood test or sometimes a urine test may be used to determine a driver’s blood alcohol concentration (BAC), the level of alcohol in his or her system.

If a driver is operating a motor vehicle while with a blood alcohol concentration of .08% or greater, he or she may be charged with DUI (VC 23152(b).

DUI for Minors

The maximum allowable limit is much lower for underage drivers who may face license suspension penalties with a BAC of .01% or greater.

DUI for Commercial Drivers

Commercial drivers may face criminal charges with a BAC of .04% or greater.

Although breath testing is the most common way to measure an individual’s blood alcohol concentration (“BAC”), it is subject to a wide variety of testing errors that may render the results unreliable. This is one of the reasons why police may falsely arrest (and prosecutors wrongfully convict) innocent people for DUI.

An Over-Simplified Explanation of Breath Testing

Although the actual detailed explanation of how breath testing works is much more complicated, this is a very general overview of how breath testing occurs.

When actual “blood” is drawn from you, the test on that blood to determine how much alcohol is in it is a direct test. In other words, the test to determine how much alcohol is in the blood is performed directly on the blood.

When the chemical test used to determine how much blood is in your system is the “breath” test then mathematical equations must be used to extrapolate from the amount of alcohol found in a small amount of your exhale, to then make the translation to determine how much alcohol is in your “blood”.

The process by which the human body gets rid of the alcohol in its blood stream occurs deep inside the lungs by way of the blood passing against a thin (approximately 0.001 millimeters) membrane, called the alveoli. As the blood pass against the alveoli membrane, the gases in the blood containing alcohol pass-through this alveoli membrane (a kind of osmosis) into the air deep in the lungs, which is then eventually exhaled.

Even after this complicated process, the “ratio” of the amount of alcohol molecules in a “breath” exhale needs to be “partitioned” using an equation called Henry’s Law, which then produces a number, which is used to determine the amount of alcohol in your “blood”.

What this all means is that, when it comes to Breath Testing, not only are there a multitude of variables, including those pertaining to the environment and atmosphere; the process used to determine the amount of alcohol in the “blood”; issues regarding the person who blew into the breath-testing machine; the machine itself, as well as the administration of the breath-test.

Even when your breath test reports that you have a BAC of 0.17%…more than twice the legal limit…if we can show the result is inaccurate and untrustworthy, the test results become worthless and unusable against you.

California law enforcement agencies use several different DUI breath testing instruments, but each device operates on infrared spectroscopy and/or fuel cell technology. Both of these technologies convert the amount of alcohol that is present in an individual’s breath into the amount of alcohol that is in that person’s blood.

This indirect conversion process frequently causes the integrity of DUI breath test results to be compromised. Factors such as one’s physiology, the environment, and procedural errors often compound the problem, leading to a large number of false DUI arrests.

A good California DUI defense lawyer is aware of these problems and knows how to convince a prosecutor, judge, and/or jury that…when present…any or all of these factors could produce an inaccurately high BAC result.


Although DUI blood testing is thought to be more reliable than DUI breath testing, its results are still subject to error and therefore open to attack. A blood test is conducted by taking a blood sample and then processing this to determine the driver’s blood alcohol concentration.

Just a few examples of how botched blood testing can lead to wrongful DUI charges can include (but aren’t limited to) blood contamination, switched blood samples, and fermented blood, just to name a few.

An experienced California DUI defense attorney knows how to identify these problems and use them to get charges reduced or dismissed. Your attorney may be able to use this to help you avoid a conviction. Find out more about breath and blood tests and DUI by contacting our firm today.

One of the advantages to blood tests over breath tests is the ability to have your blood sample preserved for future re-testing. If you choose to, your San Diego DUI defense attorney can have your blood sample retested by a private laboratory. This is called a “blood split.” Blood splits allow independent laboratories to evaluate whether blood samples have fermented or been subject to contamination. This can result in inaccurate blood alcohol levels, which can chip away at the strength of the prosecution’s case against you.

This means that if your BAC was over 0.08% , an independent laboratory may determine, through re-testing, that it only registered that high because there were inadequate levels of preservative in the blood vial to prevent fermentation.

When you submit to a DUI breath test, there is no sample to save, the breath analysis is instant. But with blood testing, you have the ability to retest the sample for fatal errors.

Whether you have been charged or arrested for a San Diego DUI, Poway DUI, La Mesa DUI, Santee DUI, Mission Valley DUI, Clairemont DUI, Point Loma DUI, La Jolla DUI, Carmel Valley DUI, Mira Mesa DUI, Pacific Beach DUI, Del Mar DUI, Carmel Valley DUI, Encinitas DUI, Oceanside DUI, Ocean Beach DUI, Escondido DUI, Vista DUI, San Marcos DUI, Carlsbad DUI or El Cajon DUI, if you’re looking for San Diego’s Best DUI Defense Attorney, you must speak with Attorney Chris Sohovich as soon as possible. Attacking DUIs is what we do best.
Contact the Law Office of Chris Sohovich now for a free case evaluation at 619-326-8161.