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The “Mouth Alcohol” Problem

One of the most common causes of falsely high breathalyzer readings is the existence of mouth alcohol.

The breathalyzer’s internal computer is making a major assumption when it captures a breath sample and then analyzes it for blood alcohol concentration (BAC): It assumes that the alcohol in the breath sample came from alveolar air — that is, air exhaled from deep within the lungs. Since we are trying to measure how much alcohol is in the blood, rather than in the breath, the computer applies a formula to translate the results. This formula is based upon the average ratio of alcohol in the breath to alcohol in the blood. This so-called partition ratio is 1 to 2100 — that is, in the average person there will be 2100 units of alcohol in the blood for every unit measured by the breathalyzer in the breath. Put simply, the machine’s computer multiplies the amount of alcohol detected in the suspect’s breath sample by 2100 and reports that as the blood alcohol level.

But what if the alcohol in the sample is not from the lungs?

Too bad: the machine doesn’t know any better. If there is even a miniscule amount of alcohol in the DUI suspect’s mouth or throat, it will be tremendously magnified by the breathalyzer and it will report a much higher BAC than the true one.

Alcohol can be found in the mouth for a number of reasons. The most obvious is that the individual has recently consumed some alcohol; it usually takes 15-20 minutes for the alcohol to dissipate through the rinsing action of saliva. Or he/she may have recently used mouthwash or breath freshener (most contain fairly high levels of alcohol) — possibly to disguise the smell of alcohol when being pulled over by police. See my earlier post, Breath Fresheners and Breathalyzers.

The most common source of mouth alcohol is from eructation (burping or belching). This causes the liquids and/or gases from the stomach — including alcohol if it is there — to rise up into the soft tissue of the esophegus and mouth, where it will stay until it has dissipated. For this reason, police officers are required to keep a DUI suspect under observation for at least 15 minutes prior to administering a breath (in reality, however, many if not most officers are unwilling to stand around watching a suspect for a quarter of an hour).

Acid reflux can greatly exacerbate this problem. As was discussed in a previous post, GERD, Acid Reflux and False Breathlayzer Results, the stomach is normally separated from the throat by a valve. When this valve becomes herniated, there is nothing to stop the liquid contents in the stomach from rising and permeating the esophegus and mouth. The contents — including any alcohol — is then later breathed into the breathalyzer. Since it has not yet been absorbed through the stomach wall and into the blood and eventually into the lungs, this alcohol should not be read as breath from the lungs and multiplied by 2100. Of course, the breathalyzer doesn’t know this. See the article by Kechagias, et al., “Reliability of Breath-Alcohol Analysis in Individuals with Gastroesophogeal Reflux Disease”, 44(4) Journal of Forensic Sciences 814 (1999).

The mouth alcohol problem can also be created in other ways. Dentures, for example, will trap alcohol for much longer than 15-20 minutes. Periodental disease can also create pockets in the gums which will contain the alcohol for longer periods. And so on…. As the American Medical Association’s Committee on Medical Problems concluded in its Manual for Chemical Tests for Intoxication (1959):

True reactions with alcohol in expired breath from sources other than the alveolar air (eructation, regurgitation, vomiting) will, of course, vitiate the breath alcohol results.

Breathalyzer Inaccuracy….It Gets Worse

The previous two posts on the physiological sources of inaccuracy in breath alcohol analysis have apparently caused considerable interest…and a number of queries. Let me be clear: Simpson is far from alone in his conclusions. Those involved in forensic alcohol analysis will generally recognize that the most recognized authorities in the field include Dubowski, Jones, Simpson and Hlastala. In the posts I quoted supporting conclusions from Dubowski and Hlastala; Jones has expressed somewhat similar views. To quote further from Professor Dubowski on physiological sources of error (as opposed to operator error or defects in the design or function of the machine itself — of which there are many):

First, not all blood and breath alcohol curves follow the Widmark pattern, nor is the elimination phase linear. Second, alcohol absorption is not always complete within 60 to 90 minutes as often claimed. Third, the peak alcohol concentration cannot be validly predicted or established in an individual instance without frequent and timely measurement of alcohol concentrations. Fourth, it is not possible to establish whether an individual is in the absorption or elimination phase, or to establish the mean overall rate of alcohol elimination from the blood or breath, from the results of two consecutive blood or breath alcohol measurements, however timed. Fifth, significantly large short-term fluctuations occur in some subjects and result in marked positive and negative departures from the alcohol concentration trend line. Sixth, short-term marked oscillation of the blood or breath alcohol concentration can occur at various points on the curve, resulting in repeated excursions of the alcohol concentration above and below a given concetration within a few minutes or for hours. Finally, no forensically valid forward or extrapolation of blood or breath alcohol concentrations is ordinarily possible in a given subject and occasion solely on the basis of time and individual analysis results.

Dubowski, "Absorption, Distribution and Elimination of Alcohol", 10 Journal of Studies on Alcohol, Suppl. 98 (1985). And those are just some of the physiological problems when trying to measure blood alcohol. We also have to consider: possible errors by the cop in operating the machine; malfunctions in the machine; design defects (there are many: see, for example, "Breathalyzers — and Why They Don’t Work" and "Why Breathalyzers Don’t Measure Alcohol"); maintenance and repair issues; calibration errors; and so on…. But, as they say in DUI law enforcement, "close enough for government work".

Breathalyzer Inaccuracy: Post-Absorptive

I’ve received considerable response to yesterday’s post, "Breathalyzer Inaccuracy: Testing During the Absorptive State", including questions concerning the accuracy of breath machines after the absorptive state. Even in the post-absorptive state — that is, when the body has reached a state of equilibrium, or uniform distribution of alcohol — there are numerous sources of error attributable entirely to physiological factors. Simpson’s research has found that breath tests are inherently unreliable, indicating uncertainty levels of 15 to 27 percent. In an article written shortly before the one cited yesterday, he noted:

Over 90% of this uncertainty is due to biological variables of the subject, and at least 23% of subjects will have their actual blood alcohol concentration overestimated. Manufacturers’ specifications for the accuracy and precision of these instruments are inconsistent with the experimental values reported in the literature and I recommend that an appropriate amount of uncertainty be reflected in the results from these breath analyzers, especially when they are used for law-enforcement purposes.

Simpson, "Accuracy and Precision of Breath Alcohol Measurements for Subjects in the Absorptive State", 33(2) Clinical Chemistry 261 (1987). Another noted expert, Professor Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington’s Medical School, concludes:

Breath testing, as currently used, is a very inaccurate method for measuring BAC. Even if the breath testing instrument is working perfectly, physiological variables prevent any reasonable accuracy…

Hlastala, "Physiological Errors Associated with Alcohol Breath Testing", 9(6) The Champion 19 (1985).

DUI Ignition Interlocks: Dangerous but Profitable

Individuals convicted of DUI are often required to have an ignition interlock device installed (at their expense) in their cars. These notoriously inaccurate and unreliable gizmos are designed to prevent the ignition from working until after the driver has breathed into a mouthpiece and registered alcohol-free (although it takes little imagination to realize that a drunk driver can start the car by simply having his passenger breathe into the device).

This latest weapon in the “war on drunk driving” has been adopted in many states with the strong lobbying of MADD — and of manufacturers who make a huge profit on the devices. Consider a story in today’s (March 16, 2005) Arizona Republic:

First-time DUI offenders could agree to equip their vehicles with an ignition interlock device to prevent drunken driving rather than face suspended driver’s licenses under a bill that breezed through the Senate on Tuesday….. Alberto Gutier, a former highway safety director lobbying for the Arizona Interlock Distributors Association, said increased sales isn’t the bill’s purpose. “It’s not about expanding the market, it’s about preventing drunk driving,” Gutier said.

The bottom line, of course, is: Do IIDs prevent drunk driving? Do they make our streets safer? MADD claims that their “research” shows they do:

Interlocks have been shown to be effective in Maryland, Alberta, California and elsewhere with results ranging from 50 to 90 percent reductions in subsequent offenses by those offenders who were assigned interlock devices, compared with those who were not….. While interlocks are not the only solution, as offenders tend to go back to their old ways once the device is off of the vehicle, they certainly keep the roads safer while these devices are in place.

Effective in California? Keep the roads safer? The California Department of Motor Vehicles has just released a study entitled An Evaluation of the Effectiveness of Ignition Interlock in California: Report to the Legislature of the State of California. Among their conclusions:

The expected effect that an IID order/restriction issued by the court would result in a lower rate of subsequent DUI convictions was not observed. (p. 7) The risk of a subsequent crash was higher for drivers installing an IID, compared to drivers not installing a device; drivers installing an IID had a risk of a subsequent crash that was 84% higher than drivers not installing an IID. (p. 10) The results of this outcome study clearly show that IIDs are not effective in reducing DUI convictions or incidents for first DUI offenders … Because there is no evidence that interlocks are an effective traffic safety measure for first DUI offenders, the use of the devices should not be emphasized. (p. 22)

Facts notwithstanding, MADD continues its campaign for ignition interlock devices, as evidenced by a Tuesday (March 15, 2005) news article in the Tallahassee Democrat:

Mothers Against Drunk Driving held its annual legislative lobbying day, urging Florida lawmakers to lower the blood-alcohol threshold that triggers “double-drunk” penalties and calling for easier authorization of ignition-interlock devices for repeat offenders….

The Future of DUI

I gave a lecture to a national organization of attorneys last week in which I was asked, among other things, to anticipate the future course of DUI laws in the United States. Bearing in mind the words of Adlai Stevenson ("We can chart our future clearly and wisely only when we know the path which has led to the present"), I predicted the following…..

DUI Laws

The Past: The original laws simply outlawed driving while impaired.

With the arrival of primitive breathalyzers, and the counsel of the American Medical Association, impairment was presumed with a blood-alcohol concentration (BAC) of .15%. Over the years this was dropped to .10%, then .08%, and finally the laws were added making the BAC — not impairment — the offense. There are now bills before state legislatures to drop it to .05%. So-called "zero tolerance" made it a crime for drivers under 21 to have even .01% BAC.

The Trend: From focusing on actual impairment, to facilitating arrests and convictions by focusing on artifical BAC levels — and, finally, to the mere presence of alcohol. The emphasis has shifted from addressing the danger (impaired drivers) to facilitating arrests and convictions.

The Future: The "zero tolerance" laws will be applied to drivers of all ages. Criminal liability will be expanded to include attempted drunk driving (regardless of lack of specific intent), as well as vicarious liability: accomplices ("aiding and abetting"), conspiracy and so-called "Dram Shop Act" liability (providing a drink to someone who may drive).


The Past: Originally, the arresting officer gave his opinion of impairment based upon his observations of driving and symptoms, as well as field sobriety tests. The emphasis shifted to increasingly sophisticated breathalyzers and to blood tests administered by nurses or technicians. However, portable and handheld breath testing devices have more recently been used at the scene to determine probable cause to arrest; the later test on a more sophisticated breathalyzer at the station continues to be used as evidence in court. Some courts are beginning to accept the portable units into evidence.

The Trend: An increasing emphasis on money and expediency rather than accuracy and reliability.

The Future: Evidentiary breathalyzers will be replaced with simpler, cheaper (and less accurate) handheld units at the scene of arrest. Blood samples will be obtained by the officer with his syringe at the scene. Saliva tests may gain acceptance.

Constitutional Rights

The Past: There has been a parade of adverse Supreme Court decisions and a steady erosion of constitutional rights in drunk driving cases — what I have called "The DUI Exception to the Constitution". These have included approval of sobriety roadblocks (Sitz v. Michigan); double jeopardy (immediate license suspensions followed by criminal prosecutions); right to counsel; self-incrimination (Neville v. South Dakota); presumptions of innocence (if .08%, then presumed under the influence; if test taken within 3 hours of driving, BAC presumed to be same as when driving); confrontation; jury trial (Blanton v. North Las Vegas); etc.

The Trend: From the protection of the citizen from police violations, to the protection of the police from legal interference.

The Future: Increasing loss of constitutional protection — notably, the complete loss of the right to a jury trial. With the clear focus on cost and expediency, DUI cases will be handled in an administrative setting as license suspensions currently are: the two procedures will simply be consolidated, although criminal penalties will remain. There may be no judge, but only an administrative hearing officer.

Federal Presence

The Past: DUI laws have always been a state-prescribed crime. With the prompting of special interest groups like MADD (Mothers Against Drunk Driving) and the desire of politicians to curry favor with voters, this has gradually changed. Using a "carrot and stick" approach with highway funds, the federal government has forced states to change their laws and penalties in such ways as: "per se" laws; .08% BAC; "zero tolerance" for drivers under 21; automatic license suspensions; standardized field sobriety tests; federally approved lists of breath testing machines.

The Trend: The federalizing of a traditionally state offense.

The Future: With the use of the Constitution’s Commerce Clause, DUI laws and penalties will become "federalized". However, without the ability (or inclination) to arrest and prosecute these crimes in the federal courts, the states will be left to continue processing them in their own courts or administrative hearings.

The New Prohibition

The Past: The Eighteenth Amendment to the Constitution was primarily a woman’s movement that ended as a failed experiment. Since then….The BAC levels for DUI have steadily dropped from .15% to .08%, and there are efforts to reduce it further. Drivers under 21 already face .01% — alcohol prohibition as to driving.

The Trend: In 1999, MADD (primarily a woman’s movement) formally changed its mission statement from drunk driving to include "the problem of underage drinking" (not underage drinking and driving). The "problem" of drinking at all is on the horizon.

The Future: The movement will again fail, this time without obtaining a constitutional amendment. This country needs alcohol and drugs too much.