Part 6: How does a DWI (driving while intoxicated) investigation in Austin, Texas work? Basics of the Breath Test Part 2

Intoxilyzer 5000, breathalyzer, breath test, dwi

Tagged with: Dwi Drunk Driving Dui Fsts

Posted on: January 8, 2014

breathalyzer or breathalyser (a portmanteau of breath and analyzer/analyser) is a device for estimating blood alcohol content (BAC) from a breath sample. Breathalyzer is the brand name for the instrument developed by inventor Robert Frank Borkenstein.  It was registered as a trademark on May 13, 1958, and is active as of 2014 but the word has become a generic trademark. This blog is about the device used for estimating blood alcohol content in Texas.

As mentioned above, most folks refer to the breath test as the breathalyzer.  Again, this is a brand name and the breathalyzer is not in use in the State of Texas.  It is like calling a copy machine a Xerox.  By way of background, I will go through some of the history of breath testing machines, how they work, and the two main types of breath testing machines before getting into the specifics of the Intoxilyzer 5000, which is the evidential machine in use in the State of Texas.  I will also discuss the Alco-sensor IV (made by Intoximeter), which is commonly used as a roadside test, but the results are inadmissible in the State of Texas.  

It has been known that ethyl alcohol (the type of alcohol you drink) has a profound effect on automobile accidents since the inception of the automobile.  Studies on the effect of alcohol on a person's ability to drive safely can be found as early as 1904.  The 1904 study showed that moderate and heavy drinkers are incapable of operating a motor vehicle safely.  

Swedish researcher Erik Widmark did the first extensive research on alcohol impaired drivers.  Widmark worked extensively in this field between 1914 and 1932.  Widmark's research was so extensive that he developed a calculation to estimate an individual's blood alcohol content without the use of any instruments.

The calculation is as follows:


EBAC is the estimated blood alcohol content.  0.806 is a constant for body water in the blood (mean 80.6%), SD is the number of standard drinks containing 10 grams of ethanol, 1.2 is a factor to convert the amount in grams to Swedish standards set by The Swedish National Institute of Public Health, BW is a body water constant (0.58 for men and 0.49 for women), Wt is body weight (kilogram), MR is the metabolism constant (0.017), DP is the drinking period in hours and 10 converts the result to permillage of alcohol.

Obviously, experts can use this same calculation based on American standards rather than the metric system.  A standard drink containing 10 grams of ethanol is 12 ounces 4% beer, 4 ounces 12% wine, 1.25 ounces of an 80 proof spirit, and 1 ounce of a 100 proof spirit.  

Widmark is so highly regarded that he is referred by many experts as the father of modern alcohol testing.  In 1938, another important scientist, Rolla Harger of Indiana University Medical School, developed the Drunkometer.  The Drunkometer was the first machine that analyzed breath for a blood alcohol content that satisfied the requirements of law enforcement.  

At the Law Offices of Jason Trumpler, P.C. we strongly recommend not driving after consuming any amount of alcohol.  Studies show that approximately 50% of all motor vehicle crashes in which death occurs are attributed to alcohol.

In the United States, alcohol related crashes result in approximately 16,000 deaths, one million injuries, and $45 billion in costs to society every year.  Clearly, the best bet is not  to drive after consuming any amount of alcohol.  This is not to mention the obvious fact that most law enforcement officers will arrest you if you smell of alcohol or appear to have been drinking at all.  There are a myriad of reasons for this, including liability for the agency should an accident happen after you were already stopped.

In 1969, the Texas Legislature passed an Implied Consent Law, which gave the authority to the Texas Department of Public Safety (DPS), through its office of the Scientific Director, to develop rules and regulations regarding breath alcohol testing throughout the state.  This lead to the Texas Breath Alcohol Testing regulations, which established the parameters by which breath alcohol testing is to be administered and regulated.  These regulations include requirements for machines, program supervision, testing methods, and operator certification.  These regulations are based on statutes, case law, recommendations from the Department of Transportation, the National Highway Traffic and Safety Administration (NHTSA), and recommendations from the National Safety Council Committee on Alcohol and other drugs.

At this point, I will digress a bit and discuss the two main types of breath testing devices.  The two most common breath testing devices in use today are fuel cell devices and infrared devices.  Both are considered to scientifically reliable if properly maintained and periodically checked for accuracy.  The Alco-sensor IV, which is the device that officers use roadside is a fuel cell device.  To put it simply, fuel cell devices use ethyl alcohol fuel and produce an electric current.  The current is then converted through some internal calculation in the instrument into a blood alcohol concentration.  The Alco-sensor IV is on United States Department of Transportation Conforming Products List of Evidential Breath Measurement Devices.  The reason that the results of these machines are inadmissible in Texas is because the machines are not maintained in compliance with the regulations regarding breath testing in the State of Texas.  It should be noted that like all Field Sobriety Tests (FSTs), roadside breath testing is completely voluntary; therefore, I strongly recommend that you politely decline to take the test along with all other FSTs.


To get more information about the conforming products list click the following link:




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