Breath Testing – Science or Science Fiction?
Even if a person has never been charged with DWI, they are probably familiar with the concept of breath testing. They have some idea that a person breathes into a machine, which provides a number. For now, law enforcement uses breath testing as the standard. The officer can get blood in three scenarios 1) the person has refused to give a breath sample, 2) the person is unconscious or in no physical condition to give a blood sample, or 3) the officer believes that the person is impaired by a substance other than alcohol. Otherwise, the officer typically takes a person to a jail or law enforcement facility to provide a breath, rather than take the person to a hospital or healthcare facility to collect a blood sample.
Breath Testing Basics
Since breath testing is typically used in most DWI cases, one important question is how does it works. First, the machine runs checks to determine accuracy, and then is ready to begin testing. Next, the person tested provides breath through a tube, which runs into the machine. Thankfully, the mouthpiece is replaced after each test. While different machines vary in their particulars, there are several common traits. For example, most machines use Infrared Spectroscopy to determine ethanol alcohol concentration. As infrared energy passes through the sample, a certain wavelength of light is given off. Then, the machine attempts to isolate and measure the concentration of ethanol alcohol. After it has determined the amount of alcohol, the machine runs the amount of alcohol recorded through an algorithm to estimate the person’s blood alcohol concentration.
Breath testing is the type of chemical analysis used in DWI cases. As mentioned before, if the officer believes a person is impaired by alcohol, blood testing is typically requested only when a driver refuses to provide a breath sample. That means that the large majority of DWI convictions are based on results from breath tests. Consequently, the accuracy of these tests is very important.