Skip to Content Top

Texas Breath Testing: .08 Is Just Another Number: 5 Problems With the Breath Test


In Texas, the only DPS approved evidentiary breath testing machine allowed is the Intoxilyzer 5000EN manufactured by CMI, Inc., in Owensboro, Kentucky. The machine uses computer processor technology from the mid 1980s. Do you remember computers in the 1980s? That’s the sophistication the government is working with to convict you of DWI, a conviction that will remain on your record the rest of your life for anyone to see. There are newer machines out there used in other states, but Texas hasn’t started nor indicated any interest in upgrading. By the way, Kentucky does not use the machine that is manufactured in their State. The following are some quick facts that are acknowledged issues with the Intoxilyzer 5000EN.

1) The law assumes you are in the elimination phase of the alcohol metabolizing process. Imagine a bell shaped curve representing your blood alcohol content as time increases after your last drink, reaches a peak, and then begins to decrease back to zero. This decrease, or back-side of the bell curve represents elimination of alcohol from your body over time. The law is .08 at the time of driving. If you are in the elimination phase when you give your breath sample, then you would necessarily be higher at the time of driving because driving would be earlier on the curve since it is sooner in time. However, the machine has no way to know when your last drink occurred. If you provide a breath sample while you’re on the front side of the curve (the absorption phase) then your BAC would have been lower at the time of driving.

2) The machine assumes we all have the same physiological make up. A man who weighs 260 pounds that drinks everyday and a woman who weighs 110 pounds that just had her first martini appear identical to the Intoxilyzer 5000. The 5000 relies on a 2100:1 partition ratio. This means for every 2100 parts of alcohol in the blood vessel, 1 part of alcohol will escape into the alveolar sac and be part of the breath The government states this number comes from an “average” partition ratios, despite the fact that an average of all partition ratio studies over the past 80 years show that it is lower, closer to 1900:1. If a person’s partition ratio is lower than 2100:1 then they are being cheated by the Intoxilyzer, if the ratio is higher than 2100:1, then they are getting a break from the machine. The longer/harder you blow the partition ratio is decreasing because the equilibrium between the blood vessel and air sac is changing (dropping) which is why the longer/harder you blow the breath score will go up.

3) Common health issues such as Acid Reflux (GERD), Diabetes, and Asthma can create false positives in the machine. Side effects from these afflictions produce molecules in the breath that look similar to alcohol. Diabetics produce acetone during ketoacidosis that is transformed into isopropanol (like rubbing alcohol). The Intoxilyzer 5000 isn’t capable of distinguishing between isopropanol and ethanol, therefore, you get an elevated breath test score, a false positive. GERD is the same thing as chronic heart-burn, caused by a defect in the lower esophageal sphincter. Essentially, alcohol stays in your stomach longer and can delay absorption allowing some alcohol to re-enter the esophagus during the breath test itself. This is problematic because unabsorbed alcohol is being read during the breath test, elevating the BAC. See more about how GERD affects the breath test here. Also, asthmatics have to be careful if their inhaler contains celbuterol, then the machine may read that interferent as ethanol.

4) The machine is not specific for ethanol. As discussed above, the body can create endogenous alcohol in people with common ailments such as diabetes. However, other interferents in the environment or foods and drinks can also be read as alcohol by the Intoxilyzer. It all comes down to chemistry. Ethanol contains the same molecular parts as many different other types of alcohol, such as isopropanol, methyl alocohol, propanol, and butanol. If anyone drinks a glass full of these other substances they will be very sick. But if you’re exposed to certain amounts over a period of time, you develop a tolerance to it. For example, someone who finishes furniture for a living is exposed to lacquer and polyurethane on a constant basis. Every day they breathe this stuff in and get it on their hands, etc. Prolonged exposure to these materials containing methyl alcohol create a piggy-back effect where the Intoxilyzer reads it the same as ethanol elevating the breath test score. OSHA has recognized the dangers of exposure to methyl alcohol in its workplace regulations. The same issues exist with people exposed to shoe polish, certain paints, and jet boat fuel.

5) Another issue with the Intoxilyzer 5000EN that doesn’t get talked about very often is Radio Frequency Interference (RFI). RFI exists in lots of things we do, it is the reason you have to turn off your electronic devices every time your plane takes off or lands. The 5000 is equipped with an RFI detector that runs from the breath hose of the machine and plugs into the side (note: if RFI detector is unplugged, very likely the machine can still run a test that will otherwise appear valid). However, this detector was designed to pick up RFI from a police radio, aka walky-talky. In today’s world where everyone has blackberries and iPhones that are constantly downloading and uploading data wirelessly, RFI presents a real challenge to the integrity of the breath test. Do police turn off their cell phones and radios when they operate the machine? There is no way to know, and no way to check, but we do it is possible for RFI to affect a breath test without the detector alerting the operator.

This is just the top of the surface for issues surrounding breath testing in Texas. New administrative regulations effective this year have done away with the collection of multiple samples and any agreement between multiple samples. More modern breath test machines are used in other states. The bottom line is that simply because you blow into a box and it prints a piece of paper that says your .08 or greater doesn’t mean you it’s accurate. If you believe the machine is wrong, and the number of drinks you had over a block time make it physically impossible for you to be a .08 or greater, then you’re probably not. Don’t let the Government tell you your intoxicated because their machine said so, hire a lawyer that has the ability to review the records of the machine and fight the accuracy of the breath test. Juries in Texas find accused persons not guilty all the time even with breath tests over .08.