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Police Manipulation of a Breathalyzer Test

In Michigan, a breath test for BAC must be taken on a DataMaster machine in order to be admissible in court. A certified officer must operate the DataMaster, and specific procedures must be followed in order to get the most accurate results. However, an officer who is trained in the use of this machine will also know ways to manipulate the readings and potentially cause you to produce a falsely high result.

To learn more about your DUI case, review our Building a Defense page.

Breath Temperature

Breath testing machines account for a number of factors in determining your BAC; one of these factors is the temperature of your breath. However, the DataMaster does not actually measure your breath temperature during testing.

Rather, it is programmed to assume that your breath temperature is a “normal” 34 degrees Celsius. This means that if your breath temperature is higher or lower than what the machine assumes it to be, the result of the test will be flawed.

Manipulating the Breath Test

Knowing this information, officers will sometimes instruct defendants to take a deep breath and blow into the machine for as long as possible—even though this will actually increase the temperature of your breath and potentially skew the results.

When you hold your breath, your lungs warm up. This is why you should breathe deeply and quickly before blowing into the machine, but never hold your breath. Additionally, the breath at the end of your exhale is warmer than the breath at the beginning. Because of this, you should not continue breathing into the machine until you are completely out of breath. Counting to six in your head while breathing into the machine should produce the proper amount of air for testing.

It is important to note that if you do not provide a sufficient breath sample, you can be cited for an implied consent violation, which is punishable by up to a two-year license suspension and six points on your driving record.