If you have been stopped by law enforcement personnel while driving and have failed or refused to take their field sobriety tests, you will next be required to have your blood alcohol level, known as BAC, tested. Most officers like to start with the breathalyzer, which supposedly measures the level of alcohol in your bloodstream by using your breath as a sample. This is an easy testing method for officers because it requires almost no work on their part. The test can be performed on the side of the road and generally only takes a minute or two to perform.
It should be noted that a breathalyzer does not measure the actual level of alcohol in the bloodstream. Instead, it estimates the number by using a series of formulas and your breath. While desktop analyzers that use infrared spectrophotometers do exist, chances are that you would have been tested using a handheld field testing device.
The breathalyzer test is performed in three simple steps. First, a mouthpiece is attached to the breathalyzer before it is turned on. Next, officers will wait for the unit to warm up and display the instruction to “blow.” You will then be asked to blow into the device for approximately four seconds while the device beeps. Finally, the device will display what it believes to be your BAC.
Most law enforcement officers and members of juries take the results of a breath test as unalterably accurate and believe that if the breathalyzer showed the BAC to be over 0.08% then the individual is guilty of a DUI. Breathalyzers certainly are more scientific than field sobriety tests are. This is due to the fact that they display objective data rather than subjective data taken from what the law enforcement officer believes he or she is seeing or hearing.
However, breathalyzer tests are not as scientific as you may think, and they have been proven to be flawed by several studies and court cases. For example, one peer-reviewed study by LaBianca, Simpson, Thompson et.al. showed that there was a 50% margin of error in results from the breathalyzer. This is huge and can mean the difference between a conviction and an acquittal. For example, if the breathalyzer shows a reading of 0.1%, which is high in every state, the real BAC could actually be anywhere between 0.05% and 0.15%. Breathalyzer readings that are below 0.1% should not be taken as definitive guilty statuses. Sadly, though, most states still take breathalyzer readings as being as accurate as blood alcohol content readings are, leading to numerous incorrect DUI convictions.
Even if the scientific workings of the breathalyzer test were accurate, numerous factors can affect the veracity of the numbers that the device gives. Many of these problems are related to equipment problems as can be seen below.
• Poor maintenance
Every breathalyzer must be properly calibrated at regular intervals to ensure that it continues to give accurate results. These devices must typically be recalibrated every six months to one year to ensure that the sensors are still working correctly and that they do not need to be adjusted.
Even with proper calibration, some devices simply malfunction and provide fluctuating readings or readings that are falsely elevated.
• Officer error
If law enforcement personnel do not follow proper protocol for using the device, it may return falsely high numbers. Personnel must take the time necessary to perform the test accurately.
• Problems with conversion ratios
Breathalyzers are designed with 2100:1 conversion ratios. However, your personal conversion ratio could be much lower or higher than this, leading to inaccurate numbers.
• Ambient temperature
The temperature around the machine as well as any wind can directly affect the results.
• Testing time
A test undertaken while your body is still absorbing the alcohol may provide much lower results than those found up to an hour later. Therefore, a test performed at the station may read much higher than would one performed on the side of the road.
Moreover, several personal and physical factors can impact your numbers displayed by the breathalyzer.
Your metabolism directly affects how quickly alcohol is absorbed into your bloodstream.
• Breathing speed
If you hold your breath prior to taking the test, your numbers could be falsely elevated while hyperventilating could falsely lower them.
• Mouth alcohol
High levels of mouth alcohol, such as could be found if you used over-the-counter cough syrup or mouthwash, can alter breathalyzer numbers.
• Breath and body temperature
• Breath and body temperature that is increased by just a few degrees can give readings that are up to 20% higher than they should be.
Officers should refrain from performing the test for at least 20 minutes after you vomit or belch.
Acid reflux allows your stomach contents to come up into your esophagus and throat, increasing mouth alcohol levels.
Long-term smokers often have falsely elevated numbers.
• Diabetes or dieting
If you have diabetes or are on a certain diets, such as the Watkins diet, you may have high levels of acetone in your breath, which can increase breathalyzer values.
If you have taken a breathalyzer test on the side of the road and the numbers have come back positive, your defense is not necessarily over. Neither is it over if you refused the test on the side of the road but submitted to it at the police station. A good attorney may be able to challenge the veracity of the breathalyzer test based on one or more of these problem areas and may be able to get your entire case tossed out of court. If a judge and jury cannot see that your guilt is definitively proven, they will not be able to convict you of a DUI. Your attorney may be able to call these problems into question himself, or he may choose to call expert witnesses to the stand who have performed studies showing the margin of error on breathalyzers.