This guide explains the science behind breath test instruments, how they work and what the limitations of them are. It will also explain the benefits and risks of taking a breath test when stopped for a DUI.
Portable Breath tests
Before you actually make a decision to provide a breath sample or refuse one, you should know what a Breathalyzer is and what it does. In Montana, law enforcement utilize two different types of breath alcohol analyzing machines. In a police cruiser, law enforcement utilize a small, hand-held device commonly known as a Portable Breath Test, PBT, or Preliminary Alcohol Screening Test. A picture of such a device is below. A PBT device reads out a measurement of the subject's deep lung alcohol concentration of their breath. Most people commonly believe these machines are testing their blood alcohol, but in reality they are testing your breath alcohol. The machine is designed to test a certain sample of air. Law enforcement is trained to have the subject blow through the disposable tube for several seconds, until the subject is almost out of air in their lungs. The tube is hollow, so the breath blows through it. However, there is a very small part of the tube that is an inlet into the PBT machine. When the subject has exhaled through the tube for several seconds, they are beginning to exhale what is called deep lung air. This is believed to give a more accurate sample of what a true blood alcohol reading would be, as it is the alveoli air that is exchanging oxygen with the blood, that is being exhaled. At that point, the officer depresses the "Set" button, which will allow the machine to capture a sample of that air running through the tube and be tested.
The Science of breath analyzation
The machine works on the science of a fuel cell. This type of fuel cell is an electrochemical sensor that reacts with alcohol. The reaction of alcohol with the fuel cell generates a number result that is shown on the display. Essentially, the more alcohol that reacts with the fuel cell, the higher the reading. This type of science does work, but there are many factors that can cast doubt upon the reading of the unit. First, these units must be constantly calibrated to ensure the fuel cell is reading correctly. Law enforcement tests these units by introducing a test gas with a known alcohol value -so they know what the reading should be. If the PBT is not reading out the correct number of the test gas, it can be adjusted with a manual screw adjustment. The fact that this machine can be adjusted by hand, and needs adjustment at times shows that fuel cells can degrade over time and become unreliable. In addition, law enforcement must wait 15 minutes from when they first encounter a subject before obtaining a breath sample. This is because any residual alcohol in the mouth can affect the reading. For example, of a driver used mouthwash just before taking a breath sample, the readout would be affected because mouthwash has alcohol in it. 15 minutes seems to be the industry standard to declare that any possible mouth alcohol would be gone and absorbed by the body prior to testing. At a jail, law enforcement utilize a different machine. This is a much larger and much more advanced machine that will also measure breath alcohol. In Montana, most agencies utilize the Intoxilyzer 8000 manufactured by CMI Inc. This machine weighs over 17 pounds and has a variety of improvements over the PBT. The Intoxilyzer 8000 utilizes infrared spectroscopy as its method of alcohol analysis, versus the somewhat archaic fuel cell method of the PBT. Without giving a science lesson, infrared spectroscopy is where infrared light passes through a sample of breath that is provided by the subject. This breath is also deep lung air, just as the PBT. Any alcohol molecules that are contained in that sample of breath will actually absorb some of the radiation of the infrared light. The machine measures the amount of infrared radiation that hits the other side of the chamber against the amount that was started with, and the difference is a measureable amount of alcohol molecules that were present in the sample.
The Intozilyzer 8000 is also more advanced that the PBT in that it allows the law enforcement operator to determine if the subject is actually blowing air into the machine, it tells the operator exactly when enough breath has been blows to obtain deep lung air, and the result is printed out on a paper, not just displayed on an LED display. Often times a subject will try to "beat" the machine by blocking the straw you blow into the machine with their tongue, or blow air out between their cheeks and the straw. The Intoxilyzer 8000 actually has an audible buzzer that indicates when a proper breath sample is being blown into it. So, if you are trying to beat the machine, it will tell the operator what you are doing. The machine also determines when deep lung air is achieved and takes the sample itself, instead of the officer pressing a button, as in the PBT. Essentially, the Intoxilyzer 8000 takes the human error of an operator out of the equation and allows the machine to do almost everything. So - should you take a breath test or refuse them? In Montana, several cities including Missoula, Montana have enacted laws that make it a misdemeanor crime to refuse breath tests. Private criminal defense attorneys in Missoula, MT will typically tell you that if you have drank more than 1 alcoholic beverage per hour, you are likely near or over .08, and you should refuse a breath test if pulled over for DUI. What advantages are there to providing a breath test and refusing a breath test? If you provide a breath test, there is really no advantage to you. A result will be generated, and if your breath alcohol is below .08, you can still be charged with a DUI. It is very rare for an officer to "unarrest" someone for DUI if they provide a breath sample below the limit. Often times, the officer will believe that a person is under the influence of alcohol and/or drugs, and that combination is also illegal and falls under the DUI laws of Montana. In reality, there is no advantage to providing a breath sample as far as prevailing in a DUI charge is concerned. The advantage in refusing a breath test is simple: there is less observable evidence against you should you have a criminal jury trial to determine your guilt. As a former prosecutor that has tried numerous DUI trials before jurors, once a juror sees the breath alcohol concentration, and it is above .08, they just roll their eyes and wonder why they are even there. Then they convict the accused. A breath result is simply too compelling of evidence to overcome at a trial. However, if there is no breath evidence in numerical form, prosecutors have a much more difficult time proving guilt beyond a reasonable doubt that a driver was under the influence. Prosecutors are stuck with evidence of Field Sobriety Testing and a video of how the accused performed those tests. That evidence is much easier to argue before a jury and much more likely to give an accused a chance at obtaining a not guilty verdict. In the end, if you have honestly had less than 1 drink per hour, then you should consider taking a breath test, as you are not likely to be over the limit. However, 1 drink per hour is somewhat uncommon, and the average person that is drinking alcohol is drinking more than that amount. If you drink more than 1 drink per hour, your chances of being over the limit are too close to risk. If you would like to discuss this matter or have other questions about breath alcohol testing, please feel free to contact one of our attorneys at the Judnich Law Office.
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