Imagine this: You’re driving home from a dinner party, having consumed a single glass of wine. Suddenly, you see flashlight blue lights in your rearview mirror. A police officer pulls you over, and you’re asked to take a breathalyzer test. The device’s reading lands you with a DUI charge.
But were you really over the limit? How accurate are breathalyzer tests?
How does a breathalyzer work?
A breathalyzer is a device used by law enforcement agencies to estimate blood alcohol content (BAC) from a breath sample.
The device includes a mouthpiece, a tube through which the suspect blows air, and a sample chamber filled with potassium dichromate where the air is captured. The alcohol reacts with the red potassium dichromate and turns it green. The degree of color change is directly related to the level of alcohol in the sample breath.
In most devices, determining the BAC involves comparing the sample to an untouched mixture. This comparison generates an electrical current, propelling the meter’s needle from its default position. The police officer then adjusts a dial to bring the needle back to the original spot. The degree to which the dial needs to be rotated indicates the alcohol level. The further the dial needs to be turned, the higher the detected alcohol level.
| BAC level | Effect on driving capabilities |
|---|---|
| 0.01-0.05 | Relaxed, a slight “buzz,” less inhibited and alert |
| 0.06-0.10 | Emotional, numb, sleepy, reduced memory and coordination |
| 0.11-0.20 | Mood shifts, mania, inappropriate behavior |
| 0.21-0.30 | Aggression, depression, impaired vision and reasoning |
| 0.31-0.40 | Unconsciousness or coma |
| 0.41 and over | Potentially fatal |
| Source: Medical News Today | |
Implied consent laws
All states have implied consent laws that require anyone who operates a vehicle to submit to a breathalyzer test if stopped by a law enforcement officer who has reasonable grounds to believe the person has been driving while under the influence of alcohol or drugs.
If the person refuses to submit to a test, they face various penalties, including license suspension. In most cases, a refusal to submit to a breathalyzer test can be used against the driver in a criminal trial.
Are breathalyzers accurate?
All breathalyzers have an inherent margin of error, meaning that, even when used properly, breath results may not be perfect.
While police-grade models tend to be generally reliable, personal breathalyzers typically exhibit a much higher margin of error.
Yet, when it comes to a DUI conviction, the term “generally reliable” hardly offers comfort. A mere .01 percent margin of error can mean the difference between testing under the legal limit (.07 percent) and over the legal limit (0.08 percent).
In fact, an extensive New York Times investigation underscored the unreliability of breathalyzer tests. The study revealed that courts in Massachusetts and New Jersey discarded more than 30,000 breathalyzer tests taken over a 12-month period because of human errors and inadequate governmental oversight. Nationwide, thousands of tests are invalidated every year.
Vermont’s toxicology lab looked at breathalyzer machines from four different manufacturers. The lab found that the CMI Intoxilyzer 8000 was “unsatisfactory” and further found that it gave inaccurate results on “almost every test.”
Nevertheless, at the time of the review, the device was already being used in Mississippi, Oregon, and Ohio. Following the review, Florida adopted the Intoxilyzer 8000. Later, an Orange County, Florida court weighed in on the issue of the accuracy of the devices, stating:
“The Intoxilyzer 8000 is a magic black box assisting the prosecution in convicting citizens of DUI. A defendant is required to blow into the box. The defense has shown significant and continued anomalies in the operation of the Intoxilyzer 8000’s operation. The prosecution argues most of the tests do not show anomalies. In fact, a high percentage of the tests may show no anomalous operation. That the Intoxilyzer 8000 mostly works is an insufficient response when a citizen’s liberty is at risk.”
What factors may lead to an inaccurate breathalyzer reading?
A number of factors can interfere with the accuracy of breathalyzer readings, such as:
- Operator error. The accuracy of a breathalyzer hinges on its proper use. For instance, to prevent mouth-alcohol contamination, the operator should observe the suspect for 15-20 minutes (commonly known as the “deprivation period”) before administering the test, ensuring the suspect doesn’t burp, vomit, or put anything in their mouth that may impact the reading. Deviating from this protocol could lead to inaccurate results.
- Poor maintenance. Breathalyzers are scientific instruments that need to be calibrated correctly and maintained. Maintenance is up to police departments that sometimes lack the willingness or expertise to properly maintain the devices. Notably, there have been reports of police departments using stale or home-brewed chemical solutions that warped results.
- Software glitches. Experts have found errors in the software integrated into breathalyzer devices. Worse still, there have been instances of police departments disabling built-in safety measures meant to preserve test accuracy and failing to update the software when necessary.
- Individual variations. Certain user-specific factors can affect test outcomes. Older women, for example, may struggle to produce enough breath to get the device to work properly. Common substances like toothpaste, mouthwash, and breath mints can distort results. Additionally, variations in metabolic rate and body temperature can impact readings.
Why don’t police officers use blood tests?
Blood tests are more accurate than breathalyzer tests, so why don’t police officers use them?
In certain instances, police can compel a health provider to draw a patient’s blood to determine blood levels of alcohol, but these tests are highly invasive and time consuming. What’s more, a 2016 United States Supreme Court ruling found that police need a warrant to administer a blood test.
The bottom line: breathalyzer tests are a lot easier to administer than blood tests.
Breathalyzer results and DUI charges
Breathalyzer results are used to ascertain whether an individual has exceeded the legal BAC limit. However, these results aren’t infallible. Given the significant penalties associated with a DUI conviction, including possible fines, license suspension, and jail time, contesting questionable breathalyzer results is imperative.
If you find yourself doubting the accuracy of your breathalyzer results, it’s a good idea to consult an experienced DUI attorney.
Learn more about blood alcohol content and the law, including implied topics such as implied consent and zero tolerance laws.