The Tennessee Highway Patrol (THP) is bringing breathalyzers back. According to a report by WSMV4 News published on April 29, 2026, THP has reversed course and will begin reintroducing breath testing into its DUI enforcement operations, a tool the agency had previously moved away from. The shift comes in the wake of mounting scrutiny over wrongful DUI arrests, raising serious questions about the reliability of officer observations alone when no chemical test is administered.
In recent years, the Tennessee Highway Patrol has not relied on breathalyzers for DUI investigations, instead requiring blood tests to establish a driver's blood alcohol content. Unlike a breath test, which a driver can be asked to perform roadside, obtaining a blood sample requires either the driver's consent under Tennessee's implied consent law or a search warrant signed by a magistrate upon a showing of probable cause. That process is more time-consuming and resource-intensive, and its limitations, particularly in cases where a warrant cannot be quickly obtained, have contributed to THP officers making DUI arrests based on field sobriety tests and observation alone, without any chemical evidence to back them up. That is the backdrop against which THP's decision to reintroduce breathalyzers should be understood.
If you or someone you know has been arrested for DUI in Tennessee, whether by THP or a local agency, understanding how breathalyzers work, what rules officers must follow before a breathalyzer result can be used against you in court, and how their results can be challenged is essential.
Why Did THP Stop Using Breathalyzers in the First Place?
The full reasoning behind THP's long-standing reluctance to use breath testing devices was never fully explained to the public, but the consequences of going without them have become impossible to ignore. WSMV4's reporting highlighted that THP officers have faced significant controversy over wrongful DUI arrests, cases in which individuals were charged based on officer observations alone, without objective chemical evidence to support those charges. Breath tests, when properly administered, provide exactly that kind of objective data. Their absence left innocent people in a difficult position with the stigma that attaches from the allegation alone.
The decision to reverse course and reintroduce breath testing is a significant one. It signals that THP leadership recognizes that field sobriety tests and officer judgment are not a sufficient substitute for chemical testing in a system that demands proof beyond a reasonable doubt.
How Does a Breathalyzer Work?
A breathalyzer, whether the portable version used on the side of the road or the more sophisticated evidentiary instrument used at a police station, measures the amount of alcohol in exhaled air. It attempts to provide an estimation of your blood alcohol content (BAC), but only an actual blood test can give a direct reading of alcohol in the bloodstream.
When you drink alcohol, it gets absorbed into your bloodstream. As your blood passes through your lungs, a small amount of that alcohol transfers into the air in your lungs and when you breathe out, that alcohol comes out with it. A breathalyzer captures that exhaled air and uses it to calculate how much alcohol is in your blood.
Things like the way the test was administered, whether the machine was properly maintained, and even your own health and physical condition on the day of the test can all affect the number that comes out.
What Can Cause Inaccurate Results?
Despite the sophistication of modern breathalyzers, results are not always accurate. Studies have shown that breathalyzer readings can vary at least 15% from actual blood alcohol levels, with roughly 23% of subjects receiving readings that exceed their true BAC. A number of factors can produce an inaccurate or falsely elevated result, including:
- Burping or suffering from acid reflux
- Vomiting prior to or during the observation period
- Using mouthwash or breath spray before the test
- Suffering from hypoglycemia or diabetes
- Recently taking certain prescription or over-the-counter medications
- Improper calibration or maintenance of the machine
- Operator error in administering the test
Law enforcement officers are well aware that breathalyzer tests are vulnerable to error. For this reason, officers are trained to take multiple readings when possible and to observe the subject carefully in the period leading up to the test. Unfortunately, even multiple readings do not guarantee accuracy, and the factors listed above can affect results without any intent or awareness on the part of the person being tested.
When Can a Breathalyzer Result Be Used Against You in Court?
A breathalyzer result does not automatically come into evidence simply because an officer administered the test. Tennessee courts have established a strict foundation that the State must lay before a breath test result can be admitted, as seen in the case of State v. Sensing, 843 S.W.2d 412 (Tenn. 1992).
Under Sensing, the testing officer must be able to testify to six specific things before the result can be introduced into evidence:
- That the tests were performed in accordance with the standards and operating procedures promulgated by the forensic services division of the Tennessee Bureau of Investigation;
- That the officer was properly certified in accordance with those standards;
- That the evidentiary breath testing instrument used was certified by the forensic services division, was tested regularly for accuracy, and was working properly when the test was performed;
- That the motorist was observed for the requisite 20 minutes prior to the test, and during that period did not have foreign matter in his or her mouth, did not consume any alcoholic beverage, smoke, or regurgitate;
- Evidence that the officer followed the prescribed operational procedure; and
- Identification of the printout record as the result of the test given to the specific person being tested.
"The breath test result merely creates a rebuttable presumption of intoxication. T.C.A. § 55–10–408(b). The State must establish the competency of the operator, the proper operation of the machine and that the testing procedures are properly followed. The defense is then free to rebut the State's evidence by calling witnesses to challenge the accuracy of the particular machine, the qualifications of the operator, and the degree to which established testing procedures were followed."
State v. Sensing, 843 S.W.2d 412, 416 (Tenn. 1992)
A Positive Test Is Not the End of Your Case
Once the State satisfies the Sensing foundation requirements and the result is admitted, the defense retains the full right to challenge it. That challenge can target the accuracy of the particular machine, the qualifications of the officer, whether proper testing procedures were actually followed, or any of the physiological and medical factors described above. Under T.C.A. § 55–10–410(e), a person who has submitted to a breath test also has a statutory right to request an independent blood test, a right that can be powerful evidence if the blood test produces a meaningfully different result.
A breath test result is not a conviction, it is simply a piece of purported evidence by the State. Our legal system guarantees every person the right to have their day in court, and the State bears the full burden of proving its case beyond a reasonable doubt before any jury can find you guilty. That is a high bar, and it is one the State must clear on every single element of the charge.
What This Means If You Are Stopped and Asked to Give a Breath Test
Submitting to a test does not mean accepting the result without scrutiny. If you are arrested for DUI following a breath test, an experienced DUI attorney will carefully examine whether the officer met all six of the Sensing requirements, whether the machine was properly certified and maintained, whether the 20-minute observation period was genuinely observed, and whether any personal health factors may have affected the reading. Gaps in any one of these areas can render the test result inadmissible or, at minimum, subject to meaningful challenge at trial.
Facing a DUI Charge in Tennessee? We Can Help.
A DUI charge, whether based on a breath test, field sobriety tests, a blood test, or all of the above, is a serious matter that can affect your job, your license, your freedom, and your future. At our firm, we understand the science behind these tests, the strict legal standards that govern their use, and the many ways in which a result that looks clear-cut on paper can be challenged in court. If you have been charged with DUI in Tennessee, do not face it alone. Contact our office today for a consultation.
Source: "Tennessee Highway Patrol reverses course on breath tests for DUI," WSMV4 News, April 29, 2026. https://www.wsmv.com/2026/04/29/tennessee-highway-patrol-reverses-course-breath-tests-dui/