Archive for March, 2005

Breathalyzer Inaccuracy: Post-Absorptive

Wednesday, March 23rd, 2005

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).


Breathalyzer Inaccuracy: Testing During the Absorptive State

Tuesday, March 22nd, 2005

In previous posts, I have explained many of the reasons why breathalyzers are inaccurate and unreliable. See, for example, "Breathalyzers — and Why They Don’t Work"; "Warning: Breathalyzer in Use"; "Convicting the ‘Average’ DUI Suspect"; "Why Breathalyzers Don’t Measure Alcohol"; "Driving Under the Influence of… Gasoline?; "How to Fool the Breathalyzer". (These and many other sources of error are explained more fully in my book, Drunk Driving Defense, 6th edition.)

One of the most common sources of error in breath alcohol analysis is simply testing the subject too early — while his or her body is still absorbing the alcohol. Let’s take a common example. At a restaurant Sarah shares a bottle of wine with a friend. She nurses one glass over a one-hour dinner. Nearing the end, another glass is poured from the bottle and she finishes this. The two friends then order an after-dinner drink. Noting the time, Sarah quickly finishes the drink and leaves. She is stopped by the police one block from the restaurant. After questioning and field sobriety tests, she is taken to a police station and tested on a breathalyzer. The machine shows her blood alcohol concentration (BAC) to be .09% — over the legal limit. She is booked for DUI and jailed.

Sarah’s true BAC, however, was much lower. If a blood sample had been taken instead of a breath test, the results would have shown only .05% — well under the legal limit. Absorption of alcohol continues for anywhere from 45 minutes to two hours after drinking or even longer. Peak absorption normally occurs within an hour; this can range from as little as 15 minutes to as much as two-and-a-half hours. The presence of food in the stomach can delay this to as much as four hours, with two hours being common. During this absorptive phase, the distribution of alcohol throughout the body is not uniform; uniformity of distribution — called equilibrium — will not occur until absoprtion is complete. In other words, some parts of the body will have a higher blood alcohol concentration (BAC) than others.

One aspect of this non-uniformity is that the BAC in arterial blood will be higher than in veinous blood (laws generally require blood samples to be veinous). During peak absorption arterial BAC can be as much as 60 percent higher than veinous. This becomes very relevant to breath alcohol analysis because the alveolar sacs in the lungs are bathed by arterial blood, not veinous: The diffusion of alcohol through the sacs and into the lung air will reflect the BAC of the body’s arterial blood. Therefore, the breath sample obtained by the machine will be reflective of pulmonary BAC — which, during absorption, will be considerably higher than veinous BAC (and higher than the BAC in other parts of the body). After extensive research, one of the most noted experts in the field of blood alcohol analysis has concluded:

Breath testing is not a reliable means of estimating a subject’s blood alcohol concentration during absorption….. There is a significant likelihood that a given subject will be in the absorptive state when tested under field conditons. Because of large differences in arterial BAC and veinous BAC during absorption, breath test results consistently overestimate the result that would be obtained from a blood test — by as much as 100% or more. In order to have some idea of the reliability of a given breath test result, it is essential to determine by some objective means whether the subject is in the absorptive or post-absorptive state. In the absence of such information, an appropriate value for the uncertainty associated with the absorptive state should be applied to all breath test results.

Simpson, "Accuracy and Precision of Breath Alcohol Measurements for Subjects in the Absorptive State", 33(6) Clinical Chemistry 753 (1987). The most recognized expert in the field, Professor Kurt Dubowski of the University of Oklahoma, agrees with Simpson: "When a blood test is allowed, an administered breath test is discriminatory, because in law enforcement practice the status of absorption is always uncertain."


“A Death of a Thousand Cuts”

Monday, March 21st, 2005

Some time ago I talked about "the future of DUI", trying to identify trends of the past and project into the future on such issues as probable laws, blood alcohol evidence, constititional rights, the growing federal presence — and the movement toward a "New Prohibition". Although I predicted that MADD's agenda of resurrecting that failed experiment would eventually fail, I was thinking of a frontal attack — that is, an amendment to the Constitution as happened before. I recently received the following insightful comments concerning that post from a good friend and one of the top half-dozen DUI attorneys in the country today, Troy McKinney of Houston:

If there is one thing that our country's politicians have learned it is that is far easier to make small incremental changes through economically motivated laws than through unfunded mandates or constitutional amendments. Over time, these small changes significantly change the landscape.

Thus, I see there being a New Prohibition, but only a statutory one that originates at the federal level. I think it is likely that the feds will impose new, increasingly onerous requirements as conditions for federal dollars — to the extent that we will have a federally imposed statutory prohibition on alcohol.

I think the future of this federal prohibition will include, within the next 20 years, all new cars being manditorily equipped with ignition interlock devices — and ones much more sophisticated and onerous than those used today — perhaps even to the extent that a positive blow will itself be a crime that is remotely reported to law enforcement at the time of the positive blow along with a continuous GPS signal for location purposes.

I can envision passive alcohol sensors in vehicles that continually sample the ambient air. Once an ignition interlock company merges with an OnStar, the stage will be set. With 16-18 million new cars a year cranked out in this country, it offers these companies a HUGE market opportunity.

I doubt that I am the first to envision the long term possibilities and it would not surprise me if some of these companies already had plans like this on the drawing board. These companies are already very active on the legislative and regulatory front and it will only increase, dramatically so in my view.

A true zero tolerance drinking and driving society will markedly affect the sale of any alcoholic beverage as well as the sale of packaged alcohol for anything but personal consumption in one's own home. This will in turn lead to an effective, although not absolute, Prohibition.

Orwell had it mostly right, he was just a bit early in his predictions.

As with so many glacial shifts in history, we are seeing no revolution, no sudden dismemberment of the Constitution, but rather something like the old Chinese torture, "the death of a thousand cuts".


“Black-and-White Fever”

Thursday, March 17th, 2005

Experienced traffic patrol officers are familiar with a phenomenon which is sometimes referred to as "black-and-white fever". That phenomenon is simply the normal reaction of most drivers to being followed by a marked police car (painted, in many jurisdictions, black and white).

As soon as the motorist becomes aware that a police car is following him, he becomes understandably apprehensive’and focuses his attention increasingly on the rear view mirror. As the officer continues to follow, the driver becomes tense, worried, and his concentration on driving is broken: He keeps his eyes more on the mirror and less on the road ahead. Each time the driver brings his eyes back to the road, he finds that he has drifted and must correct the course of the car back to the center of the lane.

The result: weaving’and, possibly, erratic movements such as sudden increases or decreases in speed (tension can cause the foot to depress the accelerator). And, of course, these are the most commonly encountered symptoms of a drunk driver on the highway. In other words, it is the very presence of the officer which tends to create the probable cause for suspecting a DUI. And after the officer pulls the driver over, he gets out and approaches the car with the very human preconception that the driver is probably intoxicated.

And, as we know from psychological studies, we tend to see what we expect to see: normally veined eyes appear "bloodshot", normally but stressed speech sounds "slurred", normal pink complexions appear "flushed", etc. These observations are quickly followed by the notoriously subjective field sobriety tests, difficult to perform under the best of conditions. Followed in turn by an arrest for DUI.


DUI Ignition Interlocks: Dangerous but Profitable

Wednesday, March 16th, 2005

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….