First, it is important to know that the Breathalyzer is no longer used in Washington State, although the term "Breathalyzer" is used by many when referring to any breath testing device. The Breathalyzer hasn't been used in Washington State DUI cases since the 1980's. A photo of it, used in an actual trial way by your author, is available via the link "The Breathalyzer" below. Washington State used the Smith & Wesson 900C breathalyzer until it was replaced by the Verax DataMaster.
How Does a Breathalyzer Work?
The subject blew into a tube and the air bubbled through a vial of chemical that the officer inserted into the machine at the beginning of the testing process. The use of wet chemicals made breath testing on the Breathalyzer a messy process. If you look at the photo of the Breathalyzer at the link below you will see that it someone put a sticker on it stating "Wipe all ampule spills." The machine did not come from the factory with this sticker on it. The officer would adjust the machine until the needle produced indicated the breath test result. Because the officer could manipulate the result, the machine garnered the nickname of the "dial a drunk" machine.
What is a DataMaster?
The DataMaster is the machine used at the time of this writing to test the breath of Washington State DUI suspects. It was first approved for use in Washington state in the late 1980's and at that time it was made by the Verax company and called the BAC Verifier. Since that time there have been a couple of variations on the initial design and the latest Washington State version is called the DataMaster CDM, manufactured by National Patents company. The machine is computerized and it records data about the breath test and machine operation that can be accessed later by defense attorneys. The data recording feature is why it is called the "DataMaster." The machine is certainly not perfect, but at least the result cannot be manipulated by hand.
How Does the DataMaster Work?
Basically, it uses a computer and infrared light. The subject blows into the machine for a minimum of five seconds, during which time the machine is comparing the intensity of the infrared light that was measured before the subject sample to the intensity of the infrared light when the sample is accepted into the machine. Because alcohol "absorbs" some infrared light at a known wavelength, the decrease in intensity of this light can be translated into a breath alcohol reading. In Washington State, two breath samples are necessary to constitute a breath test and the readings must agree within plus or minus ten percent of the average of the two. Between the breath samples, the DataMaster runs a test on an "external standard" which should be a known alcohol vapor provided through a "simulator." It must read this external standard to a certain tolerance for the machine to proceed further. Volumes have been written (see below) about this machine, but this is the essence of how it works.