By Anna 
When someone is arrested for driving under the influence, it often feels like the evidence is stacked against them from the very beginning. Police reports usually highlight failed field sobriety tests or failed breathalyzer results as irrefutable proof of impairment. However, these tests are not always as reliable as they may appear, and a skilled DUI lawyer knows how to challenge them in court. Understanding how these challenges work can make a significant difference in the outcome of a DUI case.
The Science (and Flaws) of Breathalyzer Tests
Breathalyzer devices are designed to estimate blood alcohol concentration (BAC) by measuring alcohol levels in a person’s breath. While they are widely used, they are not foolproof. A DUI lawyer may question the accuracy of these tests by looking into factors such as:
- Device Calibration: Breathalyzers require regular calibration to ensure accurate results. If law enforcement fails to follow proper maintenance procedures, the results can be unreliable.
- Operator Error: Even if the machine works properly, the officer administering the test must be trained and follow specific protocols. Mistakes in timing or procedure can lead to false readings.
- Medical Conditions: Certain medical issues, such as acid reflux or diabetes, can produce mouth alcohol that skews results.
- Environmental Factors: Residual alcohol from substances like mouthwash, cough syrup, or even workplace chemicals can cause elevated readings.
By carefully reviewing these details, a DUI lawyer can argue that the breathalyzer results should be dismissed or given less weight in court.
The Subjectivity of Field Sobriety Tests
Unlike breathalyzers, field sobriety tests (FSTs) rely entirely on physical coordination and an officer’s judgment. Common tests include walking in a straight line, standing on one leg, and following a moving object with the eyes. While they may seem straightforward, many issues can impact performance, such as:
- Nervousness: Being stopped by police and asked to perform physical tasks under pressure can cause anyone to stumble.
- Physical Conditions: Age, weight, injuries, or medical conditions can make it difficult to perform FSTs correctly—even when completely sober.
- Unfavorable Conditions: Uneven pavement, poor lighting, or bad weather can all influence how someone performs.
- Officer Bias: Since results depend heavily on an officer’s interpretation, preconceived notions or errors in observation can lead to unfair conclusions.
A DUI lawyer will often argue that these tests do not provide a truly objective measure of impairment and should not be the basis for conviction.
Building a Defense Strategy
Challenging these tests is not about denying that law enforcement plays an important role in public safety—it’s about ensuring that people are not wrongfully convicted due to faulty evidence. A defense strategy might include:
- Requesting maintenance and calibration records for the breathalyzer device.
- Cross-examining the arresting officer about how the tests were conducted.
- Presenting medical or environmental evidence that may have interfered with results.
- Bringing in expert witnesses to explain the scientific limitations of these tests.
Through this approach, a DUI lawyer can highlight weaknesses in the prosecution’s case and ensure the defendant’s rights are protected.
Why This Matters
A DUI conviction can have lasting consequences—loss of driving privileges, hefty fines, increased insurance rates, and even jail time. For this reason, it’s critical that the evidence presented in court is accurate and reliable. Breathalyzers and field sobriety tests may be common, but they are not beyond scrutiny.
Anyone facing DUI charges should understand that they have the right to question the evidence against them. By working with an experienced DUI lawyer, defendants can make sure that every aspect of the case is examined thoroughly, increasing the chances of a fair and just outcome.