The best ways to test alcohol in a DUI case


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Tag Archives: breath test

The best ways to test alcohol in a DUI case

The best ways to test alcohol in a DUI case

The best ways to test alcohol in a DUI case

A relatively new academic and research article discusses the best ways to test alcohol in a DUI case.The article in the Regulatory Toxicology and Pharmacology journal from less than a year ago entitled “Best practices approach to determination of blood alcohol concentration (BAC) at specific time points”, discusses this in detail from a forensic toxicologist research point of view.

The study notes that alcohol testing is the number one substance that is measured in the law – far more than other substances that are illegal to drive under, including prescription drugs involved in a DUI, illegal drugs involved in a DUI, and other DUID Drug DUI scenarios. In Orange County, DUID Drugs continues to be a growing problem, but the number of alcohol cases far outweighs those of drugs.

One of the problems in measuring alcohol concentrations in living, metabolizing drivers, is that the alcohol levels are always changing.  The blood or breath will have an absorption phase, where the blood alcohol increases, (leading to the rising blood alcohol defense in DUI cases), a peak at some point, and then a dissipation phase, where the blood alcohol levels decline, eventually to zero alcohol in the body.

All a breath or a blood test in a DUI can  offer is information regarding an individual driver’s alcohol level at a given time. In forensic cases, the alcohol concentration in the breath (BrAC) at the time of driving is sometimes used interchangeably with the BAC (blood alcohol content) in a DUI case, without consideration for alcohol changes in the body.

The Widmark formula and model is the best method for measuring multiple alcohol (drinks) ingested at various times with alcohol elimination rate adjustments based on individual body factors. However, when it comes to the science of forensic toxicology, real world case uncertainties will always exist.

The study identifies factors that can change the accuracy of measuring alcohol in a DUI case, including the following:

Factors causing error in a DUI breath or blood test:

  • Body mass index;
  • Liver health;
  • The state of nourishment;
  • Hydration levels, or how hydrated the driver was; and 
  • Testing errors.

All of those, or any one of those, can be used to show reasonable doubt with the blood test or breath test in a DUI.  Those same problems can be used to show reasonable doubt as to the DUI case.

(The article appears at Regul Toxicol Pharmacol. 2016 Jul;78:24-36. doi: 10.1016/j.yrtph.2016.03.020. Epub 2016 Apr 1).

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Can a breath test and a blood test from the same DUI subject have different results?

Can a breath test and a blood test from the same DUI subject have different results?

A new academic paper examines whether or not the same subjects, who should have the same alcohol factors when being tested, could have different results when blood is drawn from them, and when a breath machine tests their blood at the same time. In Orange County DUI cases, both DUI blood tests and DUI breath tests, are used to measure alcohol.

dui blood test

Published on November 20, 2015, the paper, titled “Comparison of venous blood alcohol concentrations and breath alcohol concentrations measured with Draeger Alcotest 9510 DE Evidential” was published in the Forensic Science International Journal.

Noting that most blood and breath comparisons over the past 70 years were done as either drinking trials, or using police report data, which often had discrepancies and variance in timing between the breath machine test and the extraction of blood, the study set out to test blood under realistic circumstances and using strict protocols to ensure valid measurements.

Using 78 people for the test, in Germany, the test researchers used very short timing protocols, to ensure that the breath and blood were drawn from the body fairly close to one another.

It was shown in the paper that the ratio of blood alcohol to breath alcohol had a wide discrepancy.  As measured in the group, it varied greatly (between 1571:1 and 2394:1) and the ratio was shown to increase with increasing BAC. A constant conversion factor that is suitable for variable forensic purposes could not be presented.

Can a breath test and a blood test from the same DUI subject have different results? Yes.

And that means problems for trying to correlate DUI cases between a breath test, and a blood test, which in the real world of DUI arrests are not taken together, almost ever.  Especially with high blood alcohol DUI cases, this might be a problem.  If there is a discrepancy between results, that might mean that the DUI blood testing was not accurate, or the DUI breath testing was not accurate, both, or that the actual measurement discrepancy is variable for reasons discussed in the paper.

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How to Beat a Breathalyzer Test

How to Beat a Breathalyzer Test

Laguna Beach Breath Testing in Bars

Of course, the best way to beat a breathalyzer is not to have alcohol in your system.  As a DUI defense lawyer in Orange County, that focuses on drunk driving cases only, I get asked by clients, friends, and acquaintances all the time whether I recommend that persons suspected of a DUI take a breath or a blood test.

Do you have to take a breathalyzer test?

No.  You have the right to refuse.  You have the right to refuse a field breathalyzer (also known as a PAS device, or a PBT), as they are part of the Field Sobriety Tests, which are completely voluntary.

However, you should know that not consenting to take an evidentiary test is considered a refusal.  A refusal is an automatic, in most cases irreversible, suspension of your driver’s license for one year in California.

Should I take a blood, or a breath test?

While there is a split of opinion among my colleagues that are DUI defense lawyers in the community on which is best, I generally recommend that a person take a breath test.

One of my favorite YouTube channels, ASAP Science, did a live test to see what effects various substances that are rumored to affect breath tests had on actually drunk substances.  You can see the video here:

(Other favorite YouTube channels focusing on science that I recommend are VSauce, Veritasium, CPG Grey, and Minute Physics, and our law firm also has an Miller and Associates Youtube Channel).

Note that they used what appears to be an uncalibrated instrument and tested peanut butter, honey, and a penny.  Mythbusters also did tests with other substances, with similar results.  And the news in the past few years have had stories of people trying to swallow their underwear, eating feces, and swallowing mouthwash to try to avoid being arrested for DUI. (That last substance could actually substantially increase your alcohol level).

On the DUI defense side, DUI Lawyers are always looking for substances that might create a false positive, or, compounded with actual alcohol (ethanol) create a higher blood alcohol content (BAC) result than a true reading.

Alcohol’s effect on the body is a highly tested subject, with tests comparing breath and blood levels going back decades.  It is well known that acetones, like the kind used in most paints or in industry, are a false positive for alcohol.  So, those that work around paints, solvents, or similar chemicals, can have those molecules in their skin, lungs, and show higher test values when testing is done for alcohol only.

It is interesting that the last substance they used is peanut butter.  Theoretically, if you could wash your lungs with it, the high levels of sodium, which can be found in peanut butter, could be used to neutralize ethanol by creating two byproducts – sodium ethoxide (also known as alkoxide) and hydrogen gas. But, again, the problem is that eating peanut butter involves your mouth and your your stomach, not your lungs — where the alveolar air, which is full of alcohol, is about to come from and be tested by the machine. How you would suddenly produce a jar of peanut butter inside a police station is probably the most difficult part of any attempt to “beat the breathalyzer” using this method.

One of the substances that is common in cases where an accident is involved, and is high in acetone, is the dust used on airbags.  If that is inhaled, the driver will have a higher reading for alcohol than the amount consumed.

California’s testing law, Title 17, also requires that breath testing be done in accordance with the “2/2/2” rule – that is, two tests, spaced two minutes or more apart, that must agree with a .02 of each other.  That .02% sets the breath machine’s maximum margin of error.  So, a test, can be taken at 2:00 a.m. at a .07%, and at 2:02 a.m., at a .09%, and still be considered accurate, even with different readings.

One way to keep a breath reading low is proper preparation ahead of time.  Because the alcohol molecule is hydrophilic (that is, it bonds to the water molecule evenly), being hydrated before drinking will minimize the alcohol level as a percent of body volume.  Eating before drinking also closes the pylorus, which causes absorption of alcohol to be much slower than drinking without food in the stomach.

Some factors in the mouth, like the use of listerine strips or breath sprays (or similar, all of which have alcohol), or dental work, can trap alcohol, or add alcohol, and artificially increase a breath machine result.

I have seen in DUI defense seminars, presenters blow a 0.0% on a breath measuring device, and then eat something with simple carbs, like white bread, wait, and then blow at a level with alcohol in their system.  Mouth bacteria ferments food between the teeth, and creates alcohol, that can be measured on a breathalyzer.  Some foods that are already fermented, like soy sauce, to use one common example, can register positive for alcohol on a breath testing machine immediately.

Title 17, the testing law in California, requires that the officer observe the testing subject for 15 minutes or more, to make sure that the subject does not “belch, vomit, or burp”, all of which can contaminate a test.  Often, this is not done, or the officer will record 15 minutes passing while they are out of the room, doing paperwork, or not observing the subject.

The one thing that does work (other than time, eating and being hydrated, as mentioned above, and having a properly maintained and calibrated breath device, is having a lower temperature of the air being tested.  For that reason, the air temperature within the device during testing is always recorded during a breath test.

One “trick” that law enforcement commonly uses is having testing subjects breath deeply, and hold breath, which warms up the breath.  That can artificially increase the reading, which can make a big difference in borderline cases.

The solution that works, then, is to do the opposite – hyperventilating cools down the throat, and the passage of air, and results in a slightly lower result.  That can result in a test below the legal limit, and thus would beat a DUI charge in the field.

Is there a foolproof method of going from a result above 0.08 to one below it? Nope. The best way to avoid a DUI is to not drink and drive.

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