DUI Breath Test and DUI Blood Test

If you have an upcoming DMV hearing or court case for a DUI arrest, a key part of the prosecution's evidence against you will almost certainly be the blood-alcohol concentration (BAC) determined by a breathalyzer and/or blood test you were subjected to. 

Many assume that a DUI breath or blood test result is an iron-clad piece of evidence and that, consequently, it is futile to attempt DUI defense if your BAC tested out at above the legal limit (.08%). In reality, however, both breath and blood tests are imperfect tools and are often imperfectly administered. Furthermore, medical conditions of the defendant and various other factors can affect their results as well.

At Los Angeles DUI Lawyer, we have a long track record of winning DUI defense cases for our many clients in the L.A. Area. Not by any means the only, but one of the main defense strategies we use is to challenge the BAC test results on various grounds. Below, some of the potential ways that these tests can be challenged will become apparent.

The DUI Breath Test in California

It is well known that there are additional punishments that accrue should you refuse a chemical test, due to California's "implied consent" law. However, note that implied consent only applies after you have been placed under arrest, not before.

But the breath test in California is a bit more complex than even that, for there are actually two types of breath tests. The first is the PAS (preliminary alcohol screening) test, which is part and parcel of the field sobriety tests. This test is administered before your arrest and can be legally refused (though lack of cooperation with the arresting officer is still not going to help you at the DMV or in court.) The only people who cannot legally refuse a PAS test are those under 21 and those on DUI probation.

The second type of breath test is the "evidentiary" variety, which as its name implies, is used as prime evidence against you in court (while the PAS is primarily a tool to "preliminarily" determine if you are legally drunk and need to be arrested.)

This second breath test can be taken in place of a blood test, generally according to your own preference, at the police station. Some might suppose that they can refuse the second breath test since they already took the first one (the opposite is true, however, unless you take the blood test instead.)

In the case of suspected drugged driving, you must take the blood test since a breath test will not register the results. And, if you have a medical condition that prevents you from blowing hard enough into the breathalyzer, you will have to take the blood test.

Simply refusing to take a chemical test post-arrest, however, will get you sentencing enhancements upon DUI conviction of a one-year license suspension without a restricted license and a mandatory minimum of 48 hours (extra) in county jail.

Should I Opt for Blood or Breath Test?

When given the choice, which is better — blood test or breath test? The answer is not iron-clad, but the two main factors to consider are as follows:

  • Breath tests are less reliable and less precise. This could get you a higher or lower BAC initially, but it also means it is easier to challenge a breath test result in court.
  • Breath samples cannot be saved for later re-testing, like in the blood test. This can be an advantage for the blood test, but there is no guarantee if a later independent re-test will change the result of not.

DUI Breath Test Title 17 Protocols

Under California Title 17, police must follow strict protocols in administering BAC breath tests, including the following:

  • Breathalyzers must be properly calibrated, maintained, and tested for functionality/accuracy on a regular basis.
  • Breath tests must be administered only by those specifically trained to do so with the particular device being used.
  • Police must observe the test subject for 15 minutes without interruption to ensure there is not burping, regurgitation, or anything else that would throw off the result.
  • Breath samples must be from deep-lung air. Thus, the subject must breathe deeply and blow hard into the device.
  • At least two samples must be taken, and they cannot differ significantly from each other when compared.

Challenging Breath Test Results

Breathalyzers do not directly measure BAC level (like blood tests do) but measure the amount of alcohol present in your breath and then convert it to the equivalent blood-alcohol content based on a mathematical formula. As the air deeper in the lungs will more closely match your true BAC when tested and converted, it is critical to get deep-lung air for breath tests to work properly.

How can a breath test result be challenged? In many ways. First, there could be improper calibration of the machine, misadministration, failure to adhere to the 15-minute observation period, or other Title 17 violations such as failing to re-calibrate after 10 days/150 uses. Additionally, the mouth must be checked to ensure it is empty before testing, the time at which each sample was taken must be recorded, and the mouthpiece must be firmly attached to the device.

Second, breath test results can be affected by one's diet and certain medical conditions. High-protein or low-carb diets can lead to ketone creation in your body, and ketones can convert to acetone, which is exhaled and mistaken for alcohol. Diabetics also emit ketones, and thus, should opt for the blood test to avoid a falsely high BAC reading. GERD and similar conditions that cause back-flow from stomach to mouth can also lead to high BAC results.

Third, there could be residue of alcohol in your mouth that causes a high breath test reading. It could be alcohol from drinking (even if you didn't drink enough to reach a .08% BAC in your bloodstream.) It could also be alcohol from cough syrup or mouthwash.

The "Partition Ratio Defense"

If you are charged under VC 23152a, with DUI based on actual impairment rather than on a .08 BAC level, you may be able to use the partition ratio defense. 

This defense is based on two facts: that breath tests only give approximate BAC level results and that each individual's system reacts differently to different amounts of alcohol. 

The ratio at which breath alcohol content is converted to blood alcohol content is called the "partition ratio." In California, the alcohol content found in every 2,100 ml of a breath sample is legally defined as equivalent to that found in each ml of a blood sample.

The true partition ratio that scientifically applies to each individual, however, varies, and even varies in the same person at different points in time. Thus, you may not be truly impaired at a point when someone else might be, based on the breath test and its conversion ratio.

This defense will not work when charged with DUI based on a .08% BAC, however, because California has made the 2,100 to one partition ratio a matter of statutory law.

The DUI Blood Test in California

We have looked at the DUI breath test above, but what about the blood test? As with breath tests, BAC blood tests are fallible and can be successfully challenged in court. 

First, it is possible that the blood sample was contaminated during collection. Second, the sample may have been mixed up with or even mingled with other blood samples at the police lab. Third, blood samples can ferment and produce alcohol after collection, given enough time.

Finally, there are specific protocols in Title 17 that regulate not only breath tests but also blood tests administered by police. If any of the required protocols were violated, the blood test results can become inadmissible as evidence in court. 

Title 17 protocols relevant to blood tests include:

  • The blood must be collected in a hospital, in accordance with normal medical standards, and by someone with specific training on how to properly collect it.
  • No alcohol can be used to sterilize the needle injection point. Some other sterilization method must be used.
  • Anti-coagulants and special preservatives must be placed in the vial to prevent contamination/clotting.
  • The testing equipment must be properly calibrated and maintained, and a record of maintenance must be kept.
  • The blood sample must be properly stored, and there must be a chain and record of sample custody to ensure it was not tampered with.

Can I Refuse the Blood Test?

Note that, in California, you are subject to an "implied consent" law that requires you to submit to both breath and blood tests to determine your BAC level. However, you must first be placed under arrest before you can legally be forced to submit to the chemical test. Refusal to submit to a chemical test after arrest can lead to sentencing enhancements upon a DUI conviction.

If there is no warrant issued to test your blood for alcohol content, the officer can still arrange to have this done, but refusing the test cannot be a distinct crime (according a U.S. Supreme Court ruling). By contrast, the same Supreme Court ruled that, with breath tests, it is fine for states to specifically criminalize testing refusal even when no warrant exists. 

In California, however, refusing the chemical test is a sentencing enhancement rather than a separate crime, so it is not affected by the Supreme Court's decision.

Refusing a warrant-less blood test is punishable by:

  • A mandatory one-year license suspension without possibility of a restricted license.
  • An extra 48 hours in county jail, which cannot be plea bargained away.

Warrants and Forced Blood Draws

In some cases, the arresting officer will get a warrant to draw your blood for the test, particularly if you physically refuse to submit to testing. This will enable him to have you forcibly subjected to the test in a hospital, while lab workers or other officers restrain you. It is even possible you will be unconscious while the test is being administered.

While this is not an experience anyone would want to go through, it is also a situation that often results in mistakes and failure to follow Title 17 protocols while collecting the sample. This is often used in court to get the BAC test result thrown out of court as evidence.

Challenging the Blood Test Results

There are many grounds on which the blood test results can be challenged, some of which were already mentioned above. Note that, in California, there is a "presumption" that the test results were validly obtained unless the defense attorney can prove otherwise or, at least, bring their reliability into serious doubt.

Possible contamination, fermentation in the vial, lack of adequate preservatives/anti-coagulants, poor refrigeration, or lack of proper storage records can all be a defense. In many cases, an independent blood test will be arranged by your defense attorney, using the extra samples taken by police for possible later re-testing. 

And this brings up one advantage of opting for a blood test over a breath test. There is no saved breath sample to re-test as with the blood test. And an independent lab may well get a lower BAC result, which could put you under .08%.

Contact Us Today for Help

At Los Angeles DUI Lawyer, we have the expertise to challenge the results of a DUI breath or blood test on both legal and scientific grounds (the latter, with help from a professional testing lab). By bringing your true BAC at the time of the alleged DUI incident into question, we may be able to get the charges against you dismissed, acquitted, or at least reduced.

To learn more or for a free legal consultation, contact us anytime 24/7 at 424-281-3020.

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Los Angeles DUI Defense Attorney Jeff Voll

After serving his country for 6 years as an infantry sergeant, Edward Blum left military service and went to law school. Upon graduating he took up the mantle of defending the constitution one person accused of a crime at a time. For over 20 years Edward Blum has fought and tried misdemeanor and felony criminal cases in Southern California. Edward Blum has tried hudnreds of cases from possession of drugs to murder. When he's not standing up to prosecutors, Edward Blum lectures on each citizens rights and how to interact with cops (Hint: Don't).

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