Former Municipial Court Judge

Former Assistant District Attny.

Denton County Office 940-580-2899
Collin County Office 972-954-1947

Can You Beat A Breath Test??

Tim Powers

Law Office of Tim Powers


As a highly regarded Denton County DWI Defense attorney, I invariably get asked "Well, how do I beat the breath test machine?" I always respond, "Don't worry about beating the Breath test machine. Worry about it beating you."

What I mean by this is that the machine can over-report your true Blood Alcohol Content. In other words, the alcohol in your veins can be less (sometimes very significantly less) than what the "magic" machine reports. These inaccuracies happen much more often than you might suspect.

First and foremost, the Breath Test doesn't actually test how much you have to drink. These machines are not specific to alcohol. But beyond that even if it was specific only to ethyl alcohol to the exclusion of everything else, there are still so many variables that make us all different, and make the machine far from accurate, precise and reliable. It is specifically set to test the "average person". Well, in the history of the world, the "average" person is dead, female and Chinese. Not a lot of dead people on trial. So trying to test based on the "average", isn't fair.

There are many physiological factors that can cause the Breath machine to beat you.

  1. long exhalation time into analyzer
  2. test made during the absorption phase of the blood alcohol curve when arterial venous difference in concentration of alcohol is greatest
  3. presence of mouth alcohol when breath sample was analyzed
  4. re-breathing of the first exhalation a number of times before analysis of ethanol
  5. breath holding or hypoventilation before sampling breath
  6. elevated body temperature; hyperthermia
  7. non-specific method of analysis and presence of interfering substance
  8. Partition ratio

In the United States, all breath testing devices are set in a specific way. They depend on the assumption that the ratio between alcohol in the exhaled breath in deep lung air and alcohol in the blood is 1 to 2100. This ratio is called the "Partition Ratio". To be very precise, the theory that the machine is based on is that the same weight of alcohol will be present in one cubic centimeter of pulmonary (lung) blood as in 2.1 liters of deep lung breath. However, these same exact machines in other countries have the partition ratio differently configured. For example in England, it is based upon a 1 to 2300 ratio.

Why does that matter? Well, the machine is designed to produce a reading based on that assumption. So if the assumption is wrong. The reading will be wrong every time. The truthfulness of the reading rises and falls on this one key ratio. Everyone is different. Stated more directly, not everyone has the same partition ratio. Not everyone is 1 to 2100. The actual ratio in any given individual can vary from less than 1:1300 to more than 1:3000. In fact, some peer reviewed research suggests that a person is not born with one set ratio and it can change over one's lifetime.

Additionally, 4 states have moved away from the Intoxylizer 5000 — the machine used by Denton County and Texas because they have found vase inaccuracies with the results as well as a failure of the manufactures to provide the source code to the state for verification of reliability. This is the machine that cany judge your future and possibly take away your liberty.

To make sense if all of this let's look at some real-world numbers. Suppose that the machine says that you have a 0.09 reading and you have a partition ration of 1:1700, your true Blood Alcohol Content (BAC) would be below the legal limit of 0.08. Suppose the machine reads that you have a 0.10 reading and you have a partition ration of 1:1500, your true BAC would be 0.07. So in essence, the machine has beat you.

Don't leave your Denton County, Denton, Lewisville, Flower Mound, Corinth or Highland Village DWI defense to chance.

If you are seeking aggressive criminal representation by an experienced criminal defense attorney for your Denton County DWI case or arrest in Denton County, contact the offices of Tim Powers today. There is no charge or obligation for the initial consultation. 940.580.2899.

*Tim Powers is an attorney licensed to practice law by the Supreme Court of Texas. Nothing in this article is intended to be legal advice. For legal advice about any specific legal question you should directly consult an attorney.