Do Personal Breathalyzers Prevent or Promote Drunk Driving?

Alcohol breath testing isn’t just for law enforcement anymore. One of the hottest tech items of 2014 was the personal breathalyzer. The small, handheld devices display the user’s breath alcohol concentration (BrAC), either on the item itself or by connecting to a smartphone app. In addition, some of the apps provide options to call a cab, contact a friend for a ride, or locate the nearest hotel.

Priced at $40–$150, the devices are marketed to the general public as an “accurate tool” for drinkers to track their drinking habits and evaluate their level of intoxication. And the devices are taking off in stores and online. One of the largest brands, BACtrack, states their devices are available at 15,000 retail outlets.

But the devices are coming under fire from a number of fronts. For starters, critics are concerned the devices could actually promote harmful levels of drinking by encouraging people to see just how drunk they can get, or to try to top their friends’ readings. Some users report incorporating the devices and BrAC readings into drinking games, and some devices that connect to smartphones even include games in their apps.

Equally troubling, the accuracy of the devices is questionable. A Fortune reporter recently tried out several of the most popular models and found they gave wildly different readings—varying as much as 0.03% from one brand to another. Other media outlets have had similar findings, with personal breathalyzers providing readings below those produced by corrections-grade breath alcohol testers.

That’s a problem when people may rely on portable breath testers as a guideline for driving. Law enforcement agencies and drunk driving advocates share that concern. The manufacturers state that people should not make driving decisions based on a reading. However, users who miss the fine print are likely to see a number of less than 0.08% as permission to get behind the wheel, even if they feel impaired.

Are personal breathalyzers a useful tool to help people better understand how their bodies react to alcohol, or could they actually encourage excessive drinking and impaired driving?

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Breathalyzers Report Higher Blood-Alcohol Results for Females

If you are arrested for DUI and a breath test shows a blood alcohol concentration (BAC) of .08% or higher, you are guilty. It does not matter, of course, whether you are a man or a women: the laws do not discriminate.

Maybe they should…

Researchers at the University School of Medicine in Trieste, Italy, found that the stomach lining contains an enzyme called gastric alcohol dehydrogenase that breaks down alcohol — and that women have less than men. To determine the relative effects of the enzyme, they gave alcohol both orally and intravenously to groups of alcoholic and non-alcoholic men and women. They found that women reached the same levels of blood alcohol as men after drinking only half as much; with weight differences taken into account, they found that women reached BAC levels illegal in a DUI case after drinking 20 to 30 percent less alcohol than men.

The scientists’ conclusion: legislatures may need to consider sex differences in drunk driving laws when defining safe levels of drinking for driving motor vehicles. Frezza and Lieber, "High Blood Alcohol Levels in Women: The Role of Decreased Gastric Alcohol Dehydrogenase Activity and First-Pass Metabolism", 322(2) New England Journal of Medicine 95 (1990).

Yet another study has found that women have lower "partition ratios" of blood to breath. What kind of ratios? Well, all breath machines in DUI cases measure the amount of alcohol in a person’s breath. But the what we really want to know is the amount of alcohol in the person’s blood. So how do we get that? Simple: a small computer in the breathalyzer multiplies the amount of alcohol it detects in the breath sample by 2100 times.

This is based upon the theory that, on average, there are 2100 units of alcohol in the blood for every unit of alcohol in the breath. (Note: that’s an average — but it varies from person to person.) According to the study, women have a significantly lower partition ratio. Jones, "Determination of Liquid/Air Partition Coefficients for Dilute Solutions of Ethanol in Water, Whole Blood and Plasma", Analytical Toxicology 193 (July/August 1983). And the lower the ratio, the higher the reading — even though the true BAC does not vary. Example: a woman with a true BAC of .06% and a ratio of 1500:1 (rather than the presumed 2100:1) will get a reading on the machine of .09% — above the legal limit. Put another way, the breath machine will show an average man accused of drunk driving to be innocent — but a woman with the same blood alcohol level to be guilty.

And then there’s the problem of birth control….

Scientists in Canada have found that "women taking oral contraceptive steroids (O.C.S.) appeared to eliminate ethanol significantly faster than women not taking O.C.S." Papple, "The Effects of Oral Contraceptive Steroids on the Rate of Post-Absorptive Phase Decline of Blood Alcohol Concentration in the Adult Woman, 15(1) Canadian Society of Forensic Science Journal 17 (1982). That means that women will reach peak BAC faster, and return to lower levels more quickly. This, of course, can create serious problems in a DUI case when attempting to estimate BAC at the time of driving based upon a breath test administered one hour later. Making the problem worse, researchers have also discovered that women who were taking birth control pills or who were pregnant had higher levels of acetaldehyde on their breath, due to the decreased ability to metabolize the enzyme as the level of sex steroids increases.

So what?

Well, most breath machines use infrared analysis in measuring the breath sample of a DUI suspect. But these machines don’t really measure alcohol, rather they measure any compound which contains the "methyl group" in its molecular structure. And acetaldehyde is one of these compounds. Result: a higher "blood alcohol" reading on the breathalyzer. Jeavons and Zeiner, "Effects of Elevated Female Sex Steroids on Ethanol and Acetaldehyde Metabolism in Humans", 8(4) Alcoholism: Clinical and Experimental Research 352 (1984).

It’s always a problem when the law, in its infinite wisdom, assumes that all of us are exactly the same.

This entry was posted on Saturday, May 26th, 2012 at 8:19 am and is filed under Duiblog. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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Hundreds of DUI Convictions in Doubt: Inaccurate Breathalyzers

In most drunk driving cases, by far the most important evidence comes from a breath test.  Our DUI laws even provide that they are sufficient by themselves to warrant a conviction.  The accuracy of these devices is, therefore, critical.  And I’ve posted dozens of time on the inaccuracy and unreliability of breathalyzers.  See, for example, How Breathalyzers Work — and Why They Don’t, Attorney General Finds Widespread Breathalyzer Inaccuracies: Police Shut Down All Machines and More Massive Breathalyzer Failures.

Besides the inherent inaccuracies of breath-testing devices, they are also entirely dependent upon proper maintenance and calibration by the police making the arrest. Failure to properly calibrate one of these devices on a regular basis is going to result in false readings — and wrongful convictions.

Unfortunately, cops and police agencies are notoriously lazy or incompetent when it comes to these irritating "technical" tasks….

SFPD Breathalyzer Error Puts Hundreds of DUI Convictions in Doubt

San Francisco, CA.  March 5 – Hundreds, or even thousands, of drunk driving convictions could be overturned because the San Francisco Police Department has not tested its breathalyzers, officials said Monday.

For at least six years, the police officers in charge of testing the 20 breathalyzers used by the Police Department did not carry out any tests on the equipment.

Officers instead filled the test forms with numbers that matched the control sample, said Public Defender Jeff Adachi, throwing countless DUI convictions into doubt.

“We do expect that the cases will be in the hundreds. It’s possible that it could go into the thousands. The District Attorney’s Office is still investigating the scope of this,” Adachi said during a joint news conference with District Attorney George Gascon…

Amazing….no calibration tests in six years!  The cops just made up numbers to make the machines look accurate.

Even more amazing that a reading from one of these machines is legally considered proof beyond a reasonable doubt in a DUI case — and even triggers a legal presumption of guilt, forcing an accused citizen to prove his innocence.  See Whatever Happened to the Presumption of Innocence? and How to Overcome Scientific Facts: Pass a Law. 

(Thanks to Andre Campos and Murphy Mack.)

This entry was posted on Tuesday, March 6th, 2012 at 9:40 am and is filed under Duiblog. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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