Maine Intoxilyzer Tests

Maine uses the Intoxilyzer instrument for breath alcohol testing in OUI investigations. The Intoxilyzer is a breath testing device manufactured CMI. Maine currently uses the Intoxilyzer 8000 and 9000 models.

How does the Intoxilyzer work?

The Intoxilyzer 8000 and 9000 use infrared spectroscopy to measure the alcohol level in a person’s breath. Infrared light lights measures the air a person exhales into the instrument. The instrument measures the amount of light absorbed at the infrared wavelengths to calculate the alcohol concentration in the breath sample using the Lambert-Beer Law. The amount of light absorbed at these wavelengths is used to calculate the alcohol concentration in the breath sample. The Intoxilyzer calculates the amount of alcohol in the breath sample per 210 liters of breath.

What is the Intoxiloyzer Testing Procedure?

In order for an Intoxilyzer test result to be reliable and accurate, the person performing the test must be an appropriate subject for the test, and the law enforcement officer must correctly administer the test.

Persons with facial or mouth injuries, or who are physically incapable for performing the breath test, are not appropriate subjects for a breath test according the Maine Criminal Justice Academy.

The proper procedure for a law enforcement officer in administering the Intoxilyzer test is to first make sure the person is an appropriate subject for the test. If the person is determined not to be an appropriate subject due to recent facial or mouth injuries, or physical incapabilities, then a blood test should be administered.

If the law enforcement officer determines a person is an appropriate subject for the test, the officer must follow the testing protocol below to assure the accuracy of the result.

1. Make sure the person does not have anything in his or her mouth—gum, chewing tabacco, food, retainers, removal dentures, etc. If a person has any object in his or her mouth they must be instructed to remove it.

2. Perform a mouth check. The officer must visually check the person’s mouth to assure it is empty of any foreign objects or removable dental work.

3. The officer must then observe the subject for at least 15 minutes to make sure he or she does not burp/belch, put anything in his or her mouth, or bring up any stomach content.

If the above procedure is not followed, the test results are not reliable and will often be excluded as evidence in Court or before the BMV.

How Accurate are the Intoxilyzer Test Results?

If the person is a proper subject, and the test is performed properly, the results are claimed to be accurate within 0.01 grams of alcohol per 210 liters of breath. This means a breath test with a result of 0.08 could be between 0.07 and 0.09 grams of alcohol per 210 liters of breath.

The results assume the Intoxilyzer has correctly measured and calculated the breath sample. The manufacture of the Intoxilyzer instruments, CMI, does not disclose its source codes or software to law enforcement or the public, so how the Intoxilyzer internally calculates the test result is unknown.

Factors such as residual mouth alcohol, blood in the mouth, or other substances in the breath, such as acetone, toluene, or acetaldehyde can affect the reliability of the results. The New York Times recently examined the accuracy of the breath testing devices, including the Intoxilyzer, in a 2019 article.