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Police Manipulation of a Breathalyzer Test

In Michigan, a breath test for BAC must be taken on a DataMaster machine to be admissible in court. A certified officer must operate the DataMaster, and specific procedures must be followed to obtain 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 be clear, purposeful police manipulation of breath test results is not common. This does not mean however that the police don't inadvertently do things, maybe even out of habit, that can create a falsely high result.

Breath Temperature

Breath testing machines must account for several factors in properly determining your BAC. These things include, among others, breath temperature, total breath volume and breathing pattern. However, the DataMaster does not actually measure breath temperature like some competing breath testing machines do, instead, it assumes you have a normal 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

Each of these factors above must be precisely controlled for the test result to be valid. Breath temperature, however, is not even measured, and therefore can't be directly accounted for by the machine in reaching its result. This means that anything that can impact your breath temperature can impact the test result.

It's helpful to explain it this way; when you hold your breath, your lungs warm up. Therefore 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.

What happens sometimes though is the police try to "help" you avoid an implied consent violation for failing to blow properly by repeating, as you are blowing into the machine, something like "blow harder, blow harder" or "keep going, keep going" etc. The standard instructions are "blow long and steady into the machine until I tell you to stop." The problem is the longer and harder you blow, the more likely you will blow a false high test result.

How Will You Know if Your Breath Test is Flawed?

Most police departments will video record the area where the breath testing machine is located, and this recording can be obtained through the police by your lawyer. Reviewing this video can help your lawyer determine if the test result is flawed in your case. If it is flawed, then this information can be presented to the prosecutor during plea negotiations, and if that does not pan out, can be presented to a jury at trial.

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