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Can the Results of a Breathalyzer Test Be Challenged in Court?

Authenticating a Breathalyzer sample is a three-step process in Texas

Electronic evidence, including Breathalyzer evidence, is only admissible if properly authenticated. As outlined below, authenticating a breath sample is usually a three-step process. These three steps must convince a factfinder, either a judge or a jury, that the proffered sample truly and accurately depicts the amount of alcohol in the subject’s breath at the time the test was administered.

An admissible chemical test often makes the difference between a conviction and a not-guilty verdict at trial. The chemical test DUI conviction rate is over 80%, and the non-test conviction rate is about 50 percent. If a Ft. Worth criminal defense lawyer excludes the test results on authentication grounds, prosecutors are in a very difficult position. Defense lawyers often also use authentication issues as a bargaining chip during pretrial settlement negotiations.

Probable Cause (General Authentication)

Probable cause is a legal standard of proof that’s just short of, beyond a reasonable doubt, the standard of proof at trial. Basically, the Breathalyzer must confirm a police officer’s valid suspicion that the subject is intoxicated.

Usually, the walk-and-turn and the other two Field Sobriety Tests provide the necessary probable cause. The officer’s subjective opinion that the subject “failed” these tests often does not hold up in court, but this opinion is good enough for probable cause purposes.

Legal probable cause is much harder to establish if the officer skipped the FSTs for some reason or if the defendant refused to perform them. Officers often skip FSTs if roadside test conditions are very poor or if they believe the defendant is combative. Defendants have a Fifth Amendment right to remain silent and refuse to perform tests, appear in lineups, or pose for pictures.

Additionally, the officer must administer the proper DIC-24 statutory warning. The officer must use the current version of this form, the form must be in a language the defendant understands, and all blanks must be filled out (e.g., the defendant’s name, date, time, etc.).

Device Calibration (Specific Authentication)

Usually, testimony from a police Breathalyzer technician satisfies the specific authentication requirement. Ft. Worth criminal defense lawyers often allow technicians to rant ad nauseum about the Breathalyzer’s features. Jurors know that devices with lots of bells and whistles, and therefore lots of moving parts, often break down.

Therefore, the Breathalyzer’s maintenance record is critical. That make and model must have high marks for reliability and accuracy. Furthermore, that specific device must have been recently and properly calibrated by a certified technician.

The subject’s body temperature could affect calibration as well. If the defendant was running a fever, the device must be reset to account for that elevated sample temperature. Then, the device must be reconfigured into normal mode.

Excess Mouth Alcohol (Sample Authentication)

The legal standard for intoxication is based on the grams of alcohol in the breath. So, the Breathalyzer must measure these particles and only these particles.

If the subject burped or belched prior to the test, alcohol particles from the stomach gush into the mouth and skew the breath test result. Technically, alcohol particles were in the body, but that does not matter because of the way the law is worded. The Breathalyzer must measure breath alcohol levels and only breath alcohol levels.

Prosecutors avoid this problem if the administering officer closely monitors the defendant for at least fifteen minutes prior to the test. However, courts have watered down this requirement. The monitoring period is essentially a waiting period. An officer does not even have to be in the same room as a defendant.

Therefore, there is no way to tell how much of the sample is stomach alcohol and how much is breath alcohol. The mouth alcohol problem especially makes a big difference in .08, .09, and other borderline BAC cases.

Work With a Determined Tarrant County DUI Defense Attorney

Chemical test results are not always legally up to snuff. For a confidential consultation with an experienced criminal defense lawyer in Ft. Worth, contact the Law Office of Kyle Whitaker. We routinely handle matters throughout North Texas.