Questioning Breathalyzer Calibration

Use these links to skip to different sections:

If police stop you for suspected drunk driving, an officer may administer a Breathalyzer test to check for intoxication. A Breathalyzer is a device that analyzes your breath to determine the amount of alcohol present in it and whether you are over the legal alcohol consumption limit for driving. The result this machine shows may determine whether you are arrested for driving under the influence (DUI).

Breathalyzer accuracy may not be as reliable as a blood sample, but it gives a general estimate of your blood alcohol content (BAC). Breathalyzers do not directly measure BAC, so a blood sample may still be necessary.

Can a Breathalyzer Be Wrong?

To calculate the BAC from exhaled air, the Breathalyzer multiplies the amount of alcohol in the air by the number 2,100. This number — a “partition coefficient” or “partition ratio” — reflects that the average person exhales from their lungs about 1/2100th of the alcohol amount that is currently in the blood.

This figure is an estimate at best, since the actual amount varies widely over time and from person to person. It also is subject to change due to respiration rate and body temperature.

Therefore, the results of a Breathalyzer test can sometimes be completely inaccurate. Some of the reasons why Breathalyzer results could be wrong include:

Other Substances Containing Alcohol

Sometimes, alcohol-containing substances in a person’s mouth can give off a high reading. This can happen with some toothache medicines, mouthwash, or even from burping or vomiting just prior to taking the test.

Police are actually supposed to watch a driver for approximately 20 minutes before giving the test to ensure that they do not regurgitate, belch, or put anything in their mouth that may give a false result.

Improper Calibration

Most frequently, the issue with breathalyzer accuracy is that the device is not in proper working order. Breathalyzers must be calibrated regularly and receive all required maintenance to ensure they deliver accurate results every time. An improperly maintained machine can produce unreliable test results, which a defense attorney can question in court.

How Often Are Breathalyzers Wrong?

While Breathalyzers are usually accurate, they can sometimes be wrong, especially if the officer using one doesn’t follow proper procedures. The officer should perform multiple breath tests to ensure a reliable result.

How Often Should a Breathalyzer Be Calibrated?

Each state has its own Breathalyzer calibration laws. In California, for example, Breathalyzers must be recalibrated every 10 days or 150 uses, whichever comes first. However, there are some basic guidelines that most states follow to ensure that the device’s results hold up in court. They include:

  • The Breathalyzer must be checked for accuracy at specific intervals and maintained properly.
  • The officer administering the test must be certified in the use of a Breathalyzer and perform breath tests in accordance with their training.
  • The test must consistently give two readings or more that are within .02% of each other.

Is It Bad to Refuse a Breathalyzer?

You can technically refuse a Breathalyzer, but it may not be wise to do so. Driving is a privilege, not a right. So, if you refuse a test, states can pursue a civil action to suspend your license. In addition, even if you refuse to take the test, you may be arrested anyway. In addition, the prosecutors can use the officer’s observations, other witnesses, or the results of a field sobriety test as evidence to charge you with a DUI.

Are Breathalyzers Admissible in Court?

If you can show that the police did not follow the proper procedure when using the Breathalyzer, the court will likely determine that breathalyzer results are inadmissible as evidence. This is also the case if you can prove that the Breathalyzer gives erroneous readings. Of course, the prosecution will likely argue against this happening.

The route to getting evidence deemed inadmissible is through subpoenaing the maintenance and calibration records. Then, attorneys must be able to prove that the instrument was not in proper working order.

At that point, it is the prosecution’s burden to prove that you were intoxicated using different evidence, such as poor performance on field sobriety tests. The final decision rests with the presiding judge.

How Can A DUI Attorney Help?

If you are facing a DUI charge, one of the primary pieces of evidence that can be used against you is the result of the breathalyzer test. A qualified DUI attorney can assess the validity of the breathalyzer results and other evidence presented against you and advise you on the best way to proceed.

Was this helpful?