Michigan Breath Testing in Drunk Driving Cases

Advantages and Disadvantages of Breath Testing in Drunk Driving Cases

Advantages: Breath testing is safe and unintrusive. There is virtually no risk of harm or infection to the subject being tested. Breath testing is fast and inexpensive, and evidential breath testing machines are designed to last for an extended period of time before replacement.

Disadvantages: Breath testing is an indirect form of testing for bodily alcohol levels. This means that a breath test is only circumstantial evidence of bodily alcohol content, even though it is frequently treated as direct evidence. As the body eliminates alcohol, a small portion of the alcohol is released through exhaled breath. This tiny amount of alcohol can be measured by a breath machine, and it provides an accurate estimation of the person's blood alcohol level in only the majority of cases. The amount of alcohol in a person's expired breath differs from individual to individual. Statistically, some people will provide a test sample that measures less than the true blood alcohol level. Between 3% and upwards of 20% of the public will provide a breath sample that measures higher than the true blood alcohol level. In a statistically small number of cases (but still relevant for evidential purposes), a person's breath alcohol score may be upwards of four times higher than the blood alcohol level, giving the impression that an objectively sober individual is extremely intoxicated.

Breath testing relies in large part on the proper maintenance of the breath machine, proper administration of the test, and proper screening of the breath test candidate. Maintenance, administration and screening is left almost entirely up to the local police department and the police officer performing the test. Michigan police officers are poorly trained in the area of breath testing. They are run through a quick class that details how to run a subject test and how to run a simulator test. The Michigan State Police have opted to omit almost all information about how breath testing works to the police officers that they train statewide to avoid permitting cross-examination on the scientific weaknesses that persist with breath testing.

Certain factors are known to cause elevated breath test results. If a person has a fever or higher than average breath temperature, the amount of alcohol will be perceived as being higher because the breath machine is set to accept a breath sample at specific temperature. Police officers experience this problem first hand when a simulator test goes bad and heats the testing solution too much. Officers will record a liquid/gas measurement of .08 repeatedly with a set mixture and suddenly have a breath simulator test register a .16. The amount of alcohol in the solution has not increased but because of the temperature difference, the machine perceives a higher breath score.

Another factor that is known to affect the accuracy of a breath test is the introduction of extraneous forms of alcohol. Because the breath machine is designed to measure microscopic amounts of alcohol from the deep lung air, any extraneous alcohol will result in a dramatically higher breath test result. Taking a small sip of low alcohol content beer, spitting it out and blowing into a breath machine will produce a breath result that would appear to indicate high levels of alcohol poisoning, even though the person actually has no alcohol in his or her body. Police officers would never invite a person to take a swig before testing, obviously, but this becomes a real problem when a person belches or if the person suffers from Gastroesophageal reflux disease (GERD). The tiny amount of alcohol introduced from the stomach gases can dramatically alter a breath test. This applies equally to trapped mouth alcohol that might be blown out during a breath test for people wearing dentures, a retainer or a tongue ring.

Finally, breath testing does not specifically test for alcohol, and this is a serious problem for people who have other chemicals in their body. Acetone, toluene and other organic compounds measure as if they are alcohol. These chemicals can be found in paint and paint thinners as well as a host of other industrial solvents. These chemicals can be absorbed through the skin or inhaled, and even in tiny amounts, these chemicals will create an effect that magnifies the amount of perceived alcohol in the breath sample. Diabetics will actually generate acetone and isopropanol naturally, particularly if the diabetic has consumed alcohol beverages since alcohol tends to interfere with insulin and glucose levels.

This set of videos was produced at a BAC and DMT Datamaster Breath Testing Seminar conducted on December 14, 2012.  This seminar was presented to Michigan criminal defense lawyers, and I am eternally grateful to John Fusco from NPAS (manufacturer of the Datamaster) for his generous contribution to making this seminar a success.  These videos are a bit advanced for the general public, but you can glean some valuable information about breath testing by watching these videos. 

Scroll down past the videos for additional breath testing information from the Michigan State Police. 


Datamaster Breath Test Seminar Part 1 of 7

Datamaster Breath Test Seminar Part 2 of 7

Datamaster Breath Test Seminar Part 3 of 7

Datamaster Breath Test Seminar Part 4 of 7

Datamaster Breath Test Seminar Part 5 of 7

Datamaster Breath Test Seminar Part 6 of 7

Datamaster Breath Test Seminar Part 7 of 7

Seminar Materials:

Introduction to Breath Testing Power Point

People v Morse

People v Miller



Here is a presentation from Sgt. Perry Curtis and Ken Stecker. Sgt. Curtis is in charge of the breath testing program at the Michigan State Police, and Mr. Stecker is a prosecuting attorney. A few years ago, I filed a lawsuit against the Michigan State Police pointing out the administrative rules and rule-making authority, claiming that the Datamaster handbook constituted procedures under the APA. The Michigan State Police denied this to high-heaven because it would have subjected them to attack. It appears that they have changed their tune, even though they were successful in convincing a Lansing judge that their procedural framework was all hunky dorey. The very arguments I raised in that lawsuit are detailed by Curtis and Stecker in this power point presentation. In any event, this power point presentation contains a lot of great materials for those that are unfamiliar with the Datamaster rules, procedures, and equipment. It is reproduced here without permission as a public record subject to FOIA:


Powerpoint Presentation of Sgt. Perry Curtis and Ken Stecker