Challenging Breathalyzer and Field Sobriety Test Results in San Antonio DWI Cases

A Driving While Intoxicated (DWI) charge in San Antonio often hinges on evidence obtained through breathalyzer and field sobriety tests. While these tests are frequently used by law enforcement to determine impairment, they are far from infallible. Errors in test administration, equipment malfunction, and external factors can all lead to inaccurate results.

If you’ve been charged with a DWI, a skilled San Antonio DWI attorney can challenge the validity of this evidence and build a robust defense to fight the charges against you.

Understanding Breathalyzer Tests and Their Limitations

Breathalyzer tests measure Blood Alcohol Concentration (BAC) by analyzing a sample of breath. In Texas, a BAC of 0.08% or higher is considered over the legal limit for most drivers. Despite their widespread use, these tests have significant flaws that can render results unreliable.

1. Calibration Errors
   • Breathalyzers require regular maintenance and calibration to ensure accuracy.
   • A poorly calibrated device may yield results that are higher or lower than the actual BAC.
   • Your attorney can request maintenance and calibration records to identify any issues.
2. Environmental Factors
   • Substances like mouthwash, certain medications, or even residual alcohol in the mouth can affect readings.
   • Environmental conditions, such as temperature or humidity, can also interfere with results.
3. Physiological Conditions
   • Medical conditions, such as acid reflux, diabetes, or a high-protein diet, can produce false positives.
   • Hyperventilation or shallow breathing may lead to inaccurate readings as well.
4. Improper Administration
   • Breathalyzer tests must be conducted according to strict procedures.
   • Officers who fail to observe proper protocols may compromise the accuracy of the results.

A DWI attorney can analyze these factors to determine whether the breathalyzer evidence in your case is admissible.

The Shortcomings of Field Sobriety Tests

Field sobriety tests are designed to assess a driver’s physical and cognitive abilities. Common tests include the Walk-and-Turn, One-Leg Stand, and Horizontal Gaze Nystagmus (HGN). However, these tests are subjective and prone to error.

1. Subjective Nature
   • Results often depend on the officer’s interpretation, which can be influenced by bias or lack of proper training.
   • Factors such as nerves, fatigue, or pre-existing conditions can impact a driver’s performance.
2. Physical and Environmental Factors
   • Uneven pavement, poor lighting, or inclement weather can affect test outcomes.
   • Physical conditions like age, weight, or injuries may impair a driver’s ability to perform well.
3. Improper Instructions
   • Officers must give clear and precise instructions for the tests.
   • Miscommunication or failure to demonstrate the tests correctly can lead to unfair results.

Challenging the validity of field sobriety tests requires a thorough examination of the circumstances under which they were conducted.

How a San Antonio DWI Attorney Can Help

An experienced DWI lawyer has the knowledge and resources to identify weaknesses in breathalyzer and field sobriety test evidence. Here’s how they can help:

1. Reviewing Police Reports and Body Camera Footage
   • Your attorney will scrutinize police records and video evidence to evaluate whether procedures were followed correctly.
   • Any deviations from protocol can be used to challenge the credibility of the tests.
2. Hiring Expert Witnesses
   • Expert witnesses, such as toxicologists or forensic scientists, can testify about the inaccuracies or limitations of the tests.
   • Their input can help undermine the prosecution’s case.
3. Filing Motions to Suppress Evidence
   • If evidence was obtained unlawfully or under questionable circumstances, your attorney can file a motion to suppress it.
   • Suppressed evidence cannot be used against you in court, significantly weakening the prosecution’s case.
4. Cross-Examining Law Enforcement Officers
   • During trial, your attorney can question officers about their training, experience, and adherence to protocols.
   • Highlighting inconsistencies or lack of expertise can cast doubt on the validity of the evidence.

Real-Life Impact of Challenging Test Results

Successfully challenging breathalyzer and field sobriety test results can lead to reduced charges, case dismissal, or acquittal. For example:

• If a breathalyzer was improperly calibrated, the results may be excluded from evidence.
• If field sobriety tests were conducted in unfavorable conditions, their reliability can be questioned.
• Without strong evidence of impairment, the prosecution may be forced to negotiate a favorable plea deal or drop the case altogether.

Breathalyzer and field sobriety tests are not foolproof, and their results can be successfully challenged with the help of an experienced San Antonio DWI attorney. From identifying errors in test administration to leveraging expert testimony, a skilled attorney can build a robust defense that protects your rights and your future.

If you’ve been charged with a DWI in San Antonio, don’t leave your case to chance. Contact a knowledgeable attorney who can fight to ensure you receive a fair and just outcome.