Evidence That Can Refute Breath Test Results in a DWI Case

When a person is arrested for Driving While Intoxicated (DWI) in New York, one of the most critical pieces of evidence in the prosecution’s case is the result of the breath test. This test, typically administered using a device known as a breathalyzer, is designed to measure the blood alcohol concentration (BAC) of a driver. 

If a driver's BAC exceeds the legal limit of 0.08% or higher, they can be charged with DWI. However, despite the widespread belief in the accuracy and reliability of breath tests, there are several ways that criminal defense attorneys can challenge these results in court.

Here, we’ll explore the various strategies and types of evidence that can be used to challenge breath test results in a DWI case in New York. Our experienced DWI attorney at the Law Office of Michael D. Litman, PLLC is here to help with your case in Westchester County and beyond.

1. Breathalyzer Reliability and Accuracy Issues

One of the first lines of defense in challenging breath test results is to question the reliability and accuracy of the device itself. While the Breathalyzer is generally considered a standard tool for determining BAC, it’s not infallible, and several factors can lead to inaccurate readings.

a) Calibration of the Breathalyzer Device

In New York, as in other jurisdictions, law enforcement agencies are required to confirm that Breathalyzers are properly calibrated and maintained in accordance with state regulations. 

Calibration is essential because the accuracy of a Breathalyzer device depends on its ability to correctly measure BAC levels. If a Breathalyzer is improperly calibrated, it could produce false results.

To challenge the breath test results on this basis, defense attorneys may request evidence showing that the device was calibrated according to New York State regulations.

This may include calibration logs, records of maintenance, and documentation of any repairs performed. If these records are incomplete, incorrect, or absent, it could undermine the validity of the test results.

b) Accuracy of the Breathalyzer Device

Another issue that can arise is the inherent accuracy of the device itself. Even if the Breathalyzer has been calibrated correctly, it could still produce inaccurate readings due to issues with the machine’s internal components.

Some Breathalyzer models are known to have a higher rate of error than others, and defense attorneys may seek professional testimony to show that the particular model used in the case has a higher margin of error than generally accepted.

Additionally, a professional could challenge the reliability of the machine in a specific instance, such as if the machine was malfunctioning at the time of the test. Inaccuracies can arise from a variety of factors, including electronic malfunctions, improper handling, or interference from outside sources.

c) Environmental and Biological Factors Impacting the Breath Test

Breathalyzer devices can also be affected by certain environmental or biological factors, which may lead to inaccurate results. Some common examples include:

• Mouth alcohol: If a driver recently consumed alcohol, even after drinking a small amount, the residual alcohol in the mouth can affect the test results. Breathalyzers can mistake the alcohol in the mouth for alcohol in the bloodstream, producing a falsely elevated BAC reading.

• Acetone or other chemicals: Certain medical conditions or substances in the body can affect the results of a breath test. For example, individuals with diabetes or those in a state of ketosis may produce acetone in their breath, which can interfere with the Breathalyzer’s ability to detect only ethanol (alcohol).

• Temperature and humidity: Variations in temperature and humidity in the environment where the test is administered can also impact the accuracy of the reading. The Breathalyzer may not be calibrated to account for these variations, leading to inaccurate BAC levels.

Defense attorneys can use professional testimony or cross-examination to show that these factors may have influenced the test results, casting doubt on their accuracy.

2. Improper Administration of the Breath Test

Breath tests are only reliable when they’re administered correctly. There are specific procedures that law enforcement officers must follow when administering a Breathalyzer test, and failure to follow these procedures can provide a valid basis for challenging the test results.

a) Failure to Observe the Defendant for 15 Minutes

In New York, law enforcement officers are required to observe the individual being tested for at least 15 minutes before administering the breath test. This observation period is critical to confirm that the person doesn’t regurgitate, belch, or ingest any substances that could interfere with the test results. 

If an officer fails to observe the defendant for the required period, it can be grounds for challenging the breath test results.

b) Failure to Administer the Breath Test Correctly

There are strict protocols for administering a Breathalyzer test. Officers must confirm that the device is properly used, and the defendant must blow into the machine for a sufficient period to provide an accurate sample. 

Any deviation from these procedures, such as improper handling or failure to provide an adequate breath sample, could be used to challenge the results.

c) Lack of Proper Certification or Training for the Officer

The officer administering the breath test must be certified to operate the Breathalyzer device. If the officer isn’t properly trained or certified, the defense can argue that the results may not be reliable due to improper administration of the test. 

The defense attorney may request the officer’s training records and certifications to verify whether they were qualified to administer the test.

3. Medical Conditions and Medications

Certain medical conditions and medications may interfere with the accuracy of a Breathalyzer test. As mentioned earlier, individuals with diabetes or those who are in a state of ketosis may produce acetone, which can lead to inaccurate readings. 

Other conditions, such as gastroesophageal reflux disease (GERD), can cause alcohol from the stomach to enter the mouth, which could also affect the test results.

Additionally, medications such as those containing alcohol or chemicals that mimic alcohol could produce false readings. Defense attorneys can consult medical professionals to determine whether a defendant’s medical condition or medications may have influenced the test results, providing grounds for challenging the evidence.

4. Chain of Custody and Documentation Issues

The chain of custody refers to the documentation of every step in the handling of evidence from the moment it’s collected until it’s presented in court. In a DWI case, the breath test results are considered evidence, and if there are any gaps or discrepancies in the chain of custody, it can undermine the integrity of the evidence.

Defense attorneys can challenge the breath test results by examining whether the proper chain of custody was maintained, from the collection of the breath sample to the analysis of the results. Any failure to document the proper handling of the sample can be used to cast doubt on the reliability of the evidence.

5. Professional Testimony and Cross-Examination

In many DWI cases, defense attorneys will rely on professional testimony to challenge breath test results. A professional in forensic toxicology or breath testing devices can examine the circumstances surrounding the test and provide an opinion as to why the results may not be reliable. 

These professionals can review calibration records, maintenance logs, and test results, and may even be able to conduct their own analysis to determine if the test was flawed.

During cross-examination, defense attorneys can also question the officer who administered the test, challenging their training, experience, and adherence to proper procedures.

Effective cross-examination may expose inconsistencies or weaknesses in the prosecution's case, leading to reasonable doubt about the reliability of the breath test results.

6. Alternative Explanations for Signs of Intoxication

In some cases, the defendant may have been exhibiting signs of intoxication—such as slurred speech or unsteady movements—when in fact those symptoms were caused by other factors, such as fatigue, medical conditions, or nervousness. 

If a defendant can provide an alternative explanation for their behavior, it can help to cast doubt on the breath test results.

For example, a defendant with a medical condition that causes slurred speech or difficulty walking may argue that these symptoms were mistaken for signs of intoxication. In such cases, professional testimony from medical professionals can be valuable in providing an alternative explanation for the defendant’s behavior.

Taking the First Steps

We here at the Law Office of Michael D. Litman, PLLC can assist you with any DWI case in Westchester County. We also serve the surrounding areas of White Plains, Harrison, and Yonkers. Reach out today for a second chance.