DUI Breath Tests

DUI breath tests are the most widely used methods by law enforcement during DUI investigations to determine BAC. Blood and urine tests usually require the sample to be collected by a nurse or other qualified person, who may not be present at the jail or easily reached. In addition, the person being tested may object to such invasive testing methods. These are only a few reasons why officers favor DUI breath tests as their preferred method.

Types of DUI Breath Tests

There are two different types of breath tests. The first is referred to as a preliminary breath test (PBT). This test is done before an arrest is made and it can only be used in court to show a presence of alcohol was detected. This test usually occurs on the side of the road, after the initial stop.

The second test is the state-administered test. After arrest, the driver is read an Implied Consent, which notifies the driver of consequences to refusing the test. To operate the breathalyzer machine, the operator must be certified and trained.

Breath tests use infrared spectrophotometry, or infrared absorption, uses frequencies (wavelengths) and absorption rate to determine the molecular structure of a substance. For example, the molecular formula of ethyl alcohol is CH3CH2OH (carbon, hydrogen, and oxygen atoms). The groups of atoms each have a unique frequency and will absorb infrared energy at their known wavelengths. Due to distinctive characteristics of atoms, no other substance will have the same absorption rates and we are able to determine if ethyl alcohol or another substance is present.

In DUI-DWI cases, the purpose of DUI breath testing is not to determine the presence of ethyl alcohol, but instead the concentration. Similar principles apply for quantitative testing and relies on Beer’s law, which states the amount of infrared radiation absorbed by a substance in a sample is directly proportional to the concentration of the substance in the sample. So, in breath tests, the concentration of alcohol in a breath sample is determined by the quantity of infrared absorbed and the known frequencies.

Problems with DUI Breath Testing

Machine errors should be considered with DUI-DWI breath tests. Improper calibration, or lack of routine maintenance and calibration, can cause false readings. Only by a person trained and certified to operate the breathalyzer machines. Even if the person is trained, operator errors could still happen. If a breath test result claimed a driver was near the legal limit (0.082% where the legal limit is 0.08%) or even two times the limit, a skilled criminal litigation attorney may find viable justifications as to why breathalyzer results cannot be dependable.

Residual mouth alcohol can also lead to false readings. At any given time, traces of more than 100 different substances can be present in an individual’s breath. Exhaled air can absorb alcohol from your lungs AND the upper part of the mouth and throat. Some tobacco products and products containing menthol can lead to a higher concentration reading.

Interference can also occur if another substance present in your system has frequencies similar to ethyl alcohol. For example, acetone has a similar molecular formula, CH3COCH3, with frequencies extremely similar to ethyl alcohol. Acetone can be found in the blood and breath of diabetics. This can also occur if a person is on a low-carb diet.

Additionally, gastro-esophageal reflux disorder, also known as GERD, can cause falsely high results during breath tests. GERD causes gases to leave the stomach and pass through the throat and mouth. During exhale, the escaping gases combine with any existing alcohol present in air from the lungs and cause an inaccurate higher reading.

These are just a few examples of how a DUI breath test could produce inaccurate results. Breathalyzer tests are going to be around for the foreseeable future due to their ease of use, low cost to implement, and they produce results on the spot. This allows the officer to spend less time processing one person and get back on the roads to stop another “impaired driver.” Finding legal representation trained to know the limits and faults of breath tests should be a priority if you are going to fight your DUI-DWI case in court. TeamDUI.com was created to help you find the most experienced, skilled and knowledgable criminal attorney. Each attorney on TeamDUI.com has years of experience, proven track records, and industry recognition for being in the top of their field. We are able to provide a reputable choice who is capable of analyzing the individual circumstances in your case, evaluate your chances in court, and provide you with informed options before your court date. Call us 24 hours a day at 1-844-832-6384.

Copyright 2015. William C. Head. All Rights Reserved.