Retrograde Extrapolation in DUI cases


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Tag Archives: breath testing

Retrograde Extrapolation in DUI cases

Retrograde Extrapolation in DUI cases

Retrograde Extrapolation in a DUI case

What is retrograde extrapolation?

Retrograde Extrapolation in DUI cases is a very inexact method in science.  It is the method of using existing known details to retroactively in time estimate what a blood alcohol level was at a specific time in the past.

As stated above by one of the eminent experts in alcohol issues, Dr. Dubowski has stated that retrograde extrapolation can only be accurate when done “by a person who is properly qualified by education, experience, expertise, and competence, if sufficient relevant and material information concerning the subject and the events in issue exists and is available.  Whether these conditions are satisfied in a given instance is a question of fact, which cannot be generalized.”

How is retrograde extrapolation in DUI cases used?

Retrograde extrapolation is used mainly by the prosecution in a DUI case to guess, using whatever data points exist after the fact, what the blood alcohol level for a particular person was at the time of driving.  Because the time of driving is the only relevant time where the alcohol level matters, a prosecutor has to show that a person was either impaired, or above a certain alcohol level, at that time.  It’s not illegal to be drunk, or even a high blood alcohol level, in a private space (like a police station), only when driving a motor vehicle.

Even more speculatively, the prosecution sometimes uses retrograde extrapolation to estimate the amount of drinks that the driver or defendant had before getting in the car.

What are the problems with retrograde extrapolation in DUI cases?

Blood Alcohol DUI Defenses

As you might expect, estimating blood alcohol levels depend on a number of variables, and each of those variables have their own measurement problems, and margins of error.

In the human body, blood alcohol levels do not rise and fall in a steady fashion, but instead demonstrate (through scientific testing studies), spikes or steeping of the curve towards and away from peak alcohol levels.

In the downward part of the curve, returning back to sobriety, blood alcohol elimination is often assumed to be an average of 0.015 percent per hour.  However, scientific studies show great variance in the general population from 0.008 to 0.030 percent per hour, and may vary even more than that in certain individuals.

Retrograde Extrapolation in DUI cases – Factors affecting results

Experts estimating retrograde extrapolation may not have all the information they need to make an accurate calculation.  A proper estimation, at least, would have to have all the factors below:

  1. The person at issue must be in the post peak (dissipation) of alcohol. That requires that the timing of each drink is known.
  2. The calculation must know the person’s gender.
  3. We have to know the person’s weight at the time of driving.
  4. The calculation has to know the person’s lean body mass (to obtain the volume of distribution information).
  5. You must know the person’s age.
  6. The calculation should factor for the person’s true height.
  7. The calculations performed must account for the person’s mental state.
  8. The expert must know the type of alcohol that was introduced into the body.
  9. The calculation must account for the amount of food that is in the person’s stomach, and the timing of eating, before or after drinking.
  10. We have to know the type of food in the person’s stomach.
  11. The expert should know the starting time of the drinking episode.
  12. The calculation should account for the ending time of the drinking episode.
  13. The math must account for pace of the drinking episode.
  14. The retrograde extrapolation should know whether the drinks consumed were carbonated or not;
  15. The calculations done should account for the timing between last drink and time of breath test.
  16. The expert should know the number of samples taken, and the timing of each.
  17. The model used in calculation must know the latest time of any driving.
  18. The calculation should, but in almost every case doesn’t know, the particular absorptive rate for this person.
  19. The calculation should, but in almost every case doesn’t know, the particular elimination rate for this person.
  20. The expert should know of the existence of any sort of gastro-intestinal or other diseases or conditions (lap band, GERD, acid reflux, diverticulitis or interactions with any drugs used by the person).

As you can see, the calculation is complicated.  Using retrograde extrapolation to estimate a defendant’s BAC at the time of driving has been criticized by many experts in the field. This method requires the toxicologist to make a number of assumptions; namely that the alcohol was completely absorbed at the time of testing, that the elimination of alcohol in the DUI suspect occurred at the “average” rate and that the driver’s blood-alcohol curve can be charted with accuracy.

When does the defense contradict retrograde extrapolation in DUI cases?

During the pretrial stage of a case, before trial, the defense can present any reports from forensic alcohol expert witnesses experienced with DUI cases as part of the negotiations towards a plea bargain with the prosecutor.  That may end up in a dismissal of DUI charges, reduction of charges below a DUI, or plea bargain in the DUI case.

At trial, any retrograde extrapolation done by the defense expert witness in a DUI case can also be presented to the jury.  Because the prosecutor cannot interview the DUI defendant and get all the factors above, the defense retrograde extrapolation has to be more accurate than the defense’s calculations.

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Sugar Alcohol: is it a Breathalyzer False Positive?

Sugar Alcohol: is it a breathalyzer false positive?

dui breath test
Sugar Alcohol: is it a breathalyzer false positive? As Orange County DUI Attorneys, we are often asked about what can be a false positive for breathalyzer testing.  Is It’s not surprising that any mouth alcohol–that is, ethanol or any of its chemical cousins — can be detected.  For that reason, the breath testing laws require an appropriate waiting period prior to the breath sample.
The main issue can be referred to as the various instruments’ capabilities for specificity.  That is, can it measure the specific kind of alcohol–ethanol for the purposes of testing in a DUI case –to the exclusion of any false positives for ethanol?

Sorbitol and false positives

Sorbitol is a sugar alcohol with a sweet taste which the human body metabolizes slowly.  It is used in mints, gums, toothpaste, and many sugar-free products.  Sugar alcohol is generally part of the chemical composition of sorbitol and xylitol, which is both one of many forms of alcohol derived from fruit.

Those substances are used as a sugar replacement due to its sweet characteristic in gum, food and other general consumer products.  It is slowly metabolized by the body, so DUI false positive effects for diabetics and glucose (or insulin) are minimal to none.

The problem is that all of the following are alcohol, only in different forms:

  • Ethyl alcohol;
  • Isopropyl alcohol;
  • Methanol;
  • Ethanol alcohol;
  • Glycol alcohol;
  • Sorbitol (sugar alcohol); and
  • Xylitol. 

Each will test positive for alcohol as measured by a testing device.  Breathalyzers, or any breath testing machines, that use Fuel Cell technology are well documented not to be specifically able to measure only ethyl alcohol in readings. And as our Orange County DUI Lawyer Robert Miller can tell you, ethyl alcohol is the only relevant type of alcohol to be tested in the machine for a DUI.

Sorbitol and Breath Testing

Anecdotally, many in the breath testing industry confirm that blowing into breath testing machines with sorbitol in the mouth will cause false positives.  A machine can falsely read as high as .04 for alcohol (when you are actually 0.00%) when chewing sorbitol gum or mints.

A television news crew, reporting on a DUI case that ended up being dismissed in Massachusetts, used Crest toothpaste, which contains sorbitol, and a lozenge, on a subject that had no alcohol.  The toothpaste resulted in a .04% reading on a breath testing device in that state that had read a 0.0% before the test. When repeated with the lozenge, the same result occurred.

It is not unusual for persons that have been drinking, and many that are not drinking, to have mints in their mouth with sorbitol when they are stopped by the police. As a result, the most common scenario is for the false positive reading for sugar alcohol to be added to any alcohol found in the breath, making the reading artificially high, and usually above the legal limit of a .08% alcohol level.

As with false positives for acetones, sugar alcohol can be a false positive for alcohol.  An expert witness experienced in the field of alcohol can help explain false positive breath tests to a jury and get a not guilty at trial in a DUI case.  That is done by explaining the science of how the sugar alcohol inflated the reading.

Sorbitol in the Blood as a False Positive for Alcohol

Blood sorbitol, as opposed to mouth sorbitol, is tested slightly differently.  The question for any blood test where sorbitol is involved is whether or not its presence in the bloodstream will register as ethyl alcohol on any breath machine or specifically on a breath testing device.  Those machines will typically register any alcohol in the body, including “sugar alcohol”,  even though there is no evidence that sugar alcohol makes someone drunk.

It is always a good idea in every case to talk to an alcohol expert experienced in DUI cases on the subject.  Because most breath machines can’t tell the difference between the alcohols, any sugar alcohol combined with any existing ethyl alcohol molecules will combine together, to give an artificially inflated higher reading. That can be a problem if someone was, say, a .06%, but the sugar alcohol issue tests at a .04% (as it did in the tests above).  The reading would be a .10%, putting the subject above the .08% level, even though they were actually below the legal limit.

When it comes to blood testing defenses, an expert witness will think of overlapping peaks (the alcohol curve of the sugar alcohol, plus the alcohol curve of the drinking ethyl alcohol), as an additive effect, which under what may appear to be a single peak to a more unsophisticated testing machine.

Sugar Alcohol: is it a breathalyzer false positive? How Alcohol Testing Works

Devices that use a fuel cell to measure the alcohol generally detect all alcohols that are present in the breath.  A fuel cell oxidizes the alcohol molecule in a chemical reaction.  If the alcohol would burn if a fire was applied, in general, it will react in the fuel cell.  Burning is a process of oxidizing a substance, and you know that if we remove all of the oxygen, a fire goes out.  Fuel cell machines (like the breathalyzers used in Orange County DUI cases) assume that if alcohol is reported, it only is reporting ethanol.  Sometimes that assumption is wrong.

Machines that use an infrared detection method rely upon the molecular vibrations that occur between different parts of the alcohol molecule.  For example, the Intox 8000 and 9000 depend on the vibrations that take place between the “O-H” hydroxyl portion of the molecule and the rest of the alcohol molecule.  They do this with the 9.5-micron filter they employ.  Since all alcohols have this “O-H” hydroxyl component, all of the alcohols will be reported by this measurement technique.  The analysis is very machine dependent.

There is no known or generally accepted extrapolation formula to determine the increase of the breath alcohol test result from sorbitol, xylitol etc.  The best practice is to use whole blood analysis with proper Gas Chromatograph testing.

How much of an increase from any in the blood?  That is related to, and the key issue, in a sugar alcohol false positive case. But it is in most cases unknown. In a DUI cases, it may help to show reasonable doubt to introduce this as evidence in the case.

How to Present Alcohol False Positive Information in a DUI case.

Understand that it remains the government’s burden to prove a DUI case beyond a reasonable doubt.  All the DUI defense attorney needs to do is to show problems or holes in the proof offered by the prosecutor.
The key is that it can be a significant error, and the government does not know how much higher it could have caused the reading to be either.  There is no published literature on the topic, regarding sorbitol in particular.  The mechanics of how the devices work leaves little doubt that they cannot discriminate between the different forms of alcohol, and that these forms of alcohol can be in the breath.  Trying to develop a formula for how much the result is off by is a dangerous undertaking — and usually, it is not possible, given all of the variables.
In breath testing science, you either can state that the measurement is correct or you cannot say that.  If it can be incorrect, because of any reason, including the introduction of other forms of alcohol, then you cannot trust the answer.

Contact Us For Questions.

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Sugar Alcohol: is it a breathalyzer false positive? If you have questions about the effect of sorbitol or sugar alcohols like xylitol or sorbitol on DUI breath testing machines, contact our office for a free consultation.  We are here to help.
With impeccable credentials, hundreds of great results in DUI cases, and over 22 years of courtroom and trial experience, Robert Miller is the right choice for any case where you need the help of our DUI attorneys.

Defenses to a Breath Test DUI Case

Defenses to a Breath Test DUI Case

Breath Test Defenses in a DUI

A breath test using a machine is not the end in a DUI case.  There are certainly Defenses to a Breath Test DUI case. For one, the breathalyzer machine is calibrated to the “average” person, even though in the real world of testing, there is no such thing.

Breathalyzer False Positive Factors Include the Following:

The Law of Breath Testing

Breath testing may, and may not be, mandatory, depending on the type of test performed.  A preliminary alcohol screening device, used as part of the field sobriety testing, to show the presence of alcohol, which is typically not subject to the same strict calibration and maintenance (and internal electronic checks) as an evidentiary breath test, can be refused without consequence, as all field sobriety tests can.

The exception is for those persons that are under 21 or are already on DUI probation for a conviction of Vehicle Code section 23152(a) and 23152(b), or Vehicle Code section 23103.

When a person driving a vehicle is arrested for driving under the influence, he or she is required by law to submit to a test of blood alcohol or face a one year suspension of his driver’s license, or two years if previously convicted of 23152, 23153 or 23103 CVC, within the last ten years of the date of admonition (23612 CVC / 13353 CVC), as part of the conditions of your driving privileges under California Law.

The Science of Breath Testing –  How Breath Testing Works

Breath testing devices use a fuel cell, for the most part, to heat up the air and measure the alcohol captured and measured, as a percentage of the total breath captured.

In 1954, Indiana State Police employee Dr. Robert Borkenstein invented the Breathalyzer, a type of breath alcohol testing device that is still used by law enforcement agencies today.  Because all laws regarding DUI require that drivers be below a certain blood alcohol level, breath testing devices have to assume certain averages (like lung capacity), to convert that to what a blood level is assumed to be.

The Requirements for Breath Testing

The requirements for breath testing, which are made the law in Title 17, the State’s Alcohol Testing code, requires all of the following to be a valid breath test for alcohol.

  1.  The DUI breath test must have been taken within three hours of driving.
  2. The DUI breath test must have been taken using an officially approved measuring device.
  3. The DUI breath testing machine or device must have been maintained as approved by the manufacturer’s maintenance schedule.
  4. The DUI breath test must have been taken after the subject has been observed continually for fifteen (15) minutes, during which the subject has not “belched, burped, or vomited”.
  5. The DUI breath test assumes that the subject has the average Blood Breath Partition Ratio (which averages that  2100mL of breath contain the same amount of alcohol as 1 mL of blood). That figure was given as an average figure over 45 years ago by the National Safety Council’s Committee for Tests on Intoxication.
  6. The testing subject or driver must not have GERD (acid reflux), diabetes, asthma, bronchitis, or any contaminants, including breath strips, mouthwash, dental work that traps alcohol, food in the teeth, or any acetones.  Acetones are a well known false positive for alcohol in breath tests and can be gathered in the lungs by working around paints or solvents, or by air bag dust from an auto accident.
  7. The testing subject or driver must have a standard temperature of plus or minus one degree from 34 degrees Celsius.  Having a fever, being on certain medications, trauma from an accident, exercise, or certain times of a menstrual cycle, can affect temperature.
  8. The testing device or machine must be kept at a constant temperature and must be able to adjust for atmospheric pressure, altitude, or temperature changes.
  9. The testing device or machine must be kept free from radio waves or electrical interference, which can affect the operation of the testing device, including officer radio equipment, and including cell phones.
  10. The testing device or machine must be on its own power supply, not a shared power supply with any other device.
  11.  The testing device or machine MUST be calibrated every 10 days, or every 150 uses, whichever comes first under the Title 17 law (below).
  12. The officer using the breath testing device or machine must have been specifically trained on that particular device.
  13. The breath test must follow the “2/2/2” law.  That is, the machine or device must take two acceptable breath machine samples, separated in time by at least two minutes, and those two samples must agree within a .02% of each other.

DUI Breath Testing - AlcoSensor IV Breathalyzer

Defenses to a Breath Test DUI Case

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Defenses to a Breath Test DUI Case can exist and can lead to a dismissal of a DUI case, or a reduction of a DUI case.  Call our office, or Contact Us, for information on your particular case. 

(Footnote: Title 17 reads as follows regarding breath testing--

§1221.4. Standards of Procedure. (a) Procedures for breath alcohol analysis shall meet the following standards: (1) For each person tested, breath alcohol analysis shall include analysis of 2 separate breath samples which result in determinations of blood alcohol concentrations which do not differ from each other by more than 0.02 grams per 100 milliliters. (2) The accuracy of instruments shall be determined. (A) Such determination of accuracy shall consist, at a minimum, of periodic analysis of a reference sample of known alcohol concentration within accuracy and precision limits of plus or minus 0.01 grams % of the true value; these limits shall be applied to alcohol concentrations from 0.10 to 0.30 grams %. The reference sample shall be provided by a forensic alcohol laboratory. 1. Such analysis shall be performed by an operator as defined in Section 1221.4 (a)(5), and the results shall be used by a forensic alcohol laboratory to determine if the instrument continues to meet the accuracy set forth in Section 1221.4 (a)(2)(A). (B) For the purposes of such determinations of accuracy, "periodic" means either a period of time not exceeding 10 days or following the testing of every 150 subjects, whichever comes sooner. (3) Breath alcohol analysis shall be performed only with instruments for which the operators have received training, such training to include at minimum the following schedule of subjects: (A) Theory of operation; (B) Detailed procedure of operation; (C) Practical experience; (D) Precautionary checklist; (E) Written and/or practical examination. (4) Training in the procedures of breath alcohol analysis shall be under the supervision of persons who qualify as forensic alcohol supervisors, forensic alcohol analysts or forensic alcohol analyst trainees in a licensed forensic alcohol laboratory. (A) After approval as set forth in Section 1218, the forensic alcohol laboratory is responsible for the training and qualifying of its instructors. (5) An operator shall be a forensic alcohol supervisor, forensic alcohol analyst, forensic alcohol analyst trainee or a person who has completed successfully the training described under Section 1221.4 (a) (3) and who may be called upon to operate a breath testing instrument in the performance of his duties. (6) Records shall be kept for each instrument to show the frequency of determination of accuracy and the identity of the person performing the determination of accuracy. (A) Records shall be kept for each instrument at a licensed forensic alcohol laboratory showing compliance with this Section.


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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If you are charged with a DUI, you need experienced and knowledgeable counsel to help you. Please, contact us or call our firm at (877) 942-3090.