Understanding a DUI Investigation In Michigan

Michigan DUI Investigation Process


I passed the balance and coordination tests so why do I have to take a breath test on the road? I should have been released and instead I am going to jail.

The moment a police officer suspects a motor vehicle driver has recently been drinking alcohol they will begin a standardized DUI investigation. This very specific investigation is taught to police officers all over the country. It will be very similar everywhere but that does not mean it will be performed correctly. Often times the officer receives the training only one time and their test scores for administering these tests may not have been so good. The DWI Investigation training was created by the National Highway and Traffic Safety Association (NHTSA) and is generally taught to all new officers in their training academy.

The investigation includes the administration of field sobriety tests and the administration of a preliminary breath test (PBT). It does not matter if someone passes all the tests beforehand, the PBT is still always administered if possible. And, the PBT will be one of the strongest pieces of data used to make an arrest decision. It is important to understand all phases of the DWI investigation which are described in detail below.

Phase One: Vehicle in Motion

The officer is trained to be watching the suspects driving before he pulls you over. He (she) will be looking for anything that is typically associated with impaired driving. There is a list of about 35 things like swerving, changing speeds or almost striking objects.

Phase Two – Personal Contact

This phase includes their observations when approaching and interviewing the driver. It is during this phase when they will decide whether to ask the driver to exit the vehicle for additional testing. They will begin with questions about how much, what, where and when the suspect drank alcohol. They may ask where the driver came from and where they were going to see if the answers make sense. They will also be very observant when the have first contact with the driver looking at the condition of their clothing, eyes and particular odors like intoxicants. The first two cognitive tests are the alphabet test (never have I seen them ask to do it backwards) and the number counting test (which is always backwards). The officer will be looking for a variety of things including speech, accuracy and visual observations like swaying. Those are both non-standardized tests meaning there is not a standard manner of administration and evaluation unlike the three tests that follow.

The officer may also ask for two things simultaneously as they are trained that possible signs of impairment will be displayed in response to this dual request. For instance the driver may forget to produce both documents, produce documents other than the ones requested, fails to see or overlooks one document while searching for the other, fumbles or drops their wallet or purse.

They may ask distracting or interruptive questions during this process. For instance, while retrieving the license the officer may ask “without looking at your watch, what time is it?” and observe whether the driver ignores the question, answers the question but then forgets to resume obtaining their requesting documents, or supplies grossly incorrect information.

The officer will be very observant in the manner the driver exists the vehicle when requested. Impaired drivers may do the following: have difficulty opening the door, uses the door for leverage and keeps hands on the vehicle for balance.

Phase Three – Field Sobriety Tests and Breath Test

There are three psychophysical tests called standardized field sobriety tests which are to be administered and evaluated in a very specific standardized manner. Significant deviation from the standardized administration and evaluation can invalidate the test.

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HGN Test

The first standardized test is an eye examination called the Horizontal Gaze Nystagmus. Using a pen or finger held 12 inches from your head at eye level they will move it back and forth looking for nystagmus which is “eye jerking”. When a person drinks alcohol it keeps their eyes from moving smoothly. It is noticeable and indicative of alcohol intoxication when performing this test correctly and in the standardized manner. The officer is looking for six clues total, three in each eye. Four or more clues observed is a fail.

Walk and Turn

The second test is the walk and turn where the subject starts with their right foot heel touching the toe of the left. This is the instructional stance during which the test is described and demonstrated. When instructed the subject will take nine heel to toe steps forward on an imaginary strait line, turn with small steps of their right foot then return nine heel to toe steps, all counting out loud and keeping their arms by their sides the entire time. The officer is looking for several clues. Starting without being instructed, walking off the line, wrong number of steps, not turning as instructed, not walking heel to toe and lifting arms from their sides more than six inches are all clues. Two or more clues observed is a fail.

One Leg Stand

The third test is a one leg stand. The subject is instructed to lift one leg of their choosing approximately six inches off the ground and count to thirty. The officer is looking for clues including starting before being instructed to do so, putting the foot down and raising arms for balance. Two or more clues observed is a fail.

Preliminary Breath Test on Street V. Datamaster Breath Test in Police Station

Possibly the most commonly confused thing is the difference and purpose of the breath test offered in the street in comparison to the breath test offered in the police station.

The breath test offered in the street or on the scene of the investigation is called a preliminary breath test (PBT). The technology used in estimating a person’s breath alcohol content is not as sophisticated or accurate as the one in the police station. It is subject to more error. It is not specific to the alcohol contained in beverage drinks (ethyl alcohol) meaning it will test positive for other types of alcohol as well. For that reason it is only used to make an arrest decision and not for purposes in determining guilt or innocence. The penalty for refusing to submit to a PBT is only a fine with no license sanction as long as the vehicle in operation was not a commercial vehicle.

The breath test in the police station is called the Datamaster DMT. It utilizes infrared light spectroscopy which identifies ethanol molecules by a particular chemical bond using light absorption detection. It is specific to ethyl alcohol and is much more scientifically reliable for determining bodily alcohol content. It is the only chemical instrument used in Michigan for breath alcohol analysis for evidentiary purposes. That means the Datamaster results are the only results that can be used in court to prove guilt. Refusal to submit to a Datamaster test can result in a six month license suspension and will generally be followed by the issuance of a search warrant to obtain a blood sample.

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Can They Arrest Me If I Did Not Take The PBT

A police officer can only arrest a suspected driver if, based upon everything they observed, the evidence is supported by probable cause that the driver is likely driving while intoxicated. Probable cause means evidence that would make a reasonably prudent person believe that a crime had been committed. If the driver submitted to a PBT which exceeded .08 BAC, probable cause exists even if the other tests were passed. The reason is that a person can have no psychomotor impairment and still have a unlawful BAC. If the PBT is refused, the officer must evaluate the rest of the evidence to determine if probable cause exists. If a suspected driver passed the sobriety tests then an arrest should not occur.

Can Their Standardized Tests Be Challenged In Court

If the arrest decision was made primarily upon the results of the field sobriety tests and without a PBT result that equaled or exceeded .08 BAC the suspected driver should consider challenging the sufficiency of probably cause for the arrest in court. Many officers do not administer the SFST’s correctly. If they don’t the arrest is subject to challenge which could cause the case to be dismissed.

Can The PBT Be Challenged In Court

There are rules for the administration of the PBT as well. It cannot be administered without a 15 minute period during which time nothing shall be placed inside the subject’s mouth. Additionally the officer must have been properly trained and certified to operate the PBT. Should the requirements not be met, the PBT results can be excluded from the probable cause arrest determination.

The Field Sobriety Test Training Manual can be found using this link: NHTSA Student DWI Detection Training Manual


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2018-07-17T09:40:47-04:00December 11th, 2016|