Baker Legal Services llc

(660) 287-3098 // Contact Us // Pay Online
Find Us on Facebook

DWI/DUI Defense

How does a DWI investigation work?


I just got arrested for DWI. What should I do?
How does a DWI investigation work?
The breath test said I had a blood alcohol content over the legal limit. Do I have a defense?
What is a partition ratio and how does it affect a breath test?
What do I need to worry about concerning my driver's license?
I cannot afford to have my license suspended or revoked. Is there anything I can do?
Beware the cheap lawyer!

The National Highway Traffic Safety Administration (NHTSA) has established protocols for detecting impaired drivers. These protocols are based on decades of scientific research. When the officer properly performs a DWI investigation in accordance with NHTSA’s procedures, the officer will likely arrest impaired drivers and let the non-impaired drivers go. But if the officer makes a mistake, the results of the investigation can become unreliable. This section outlines how an officer should conduct a typical investigation.

Much of a DWI investigation is based on the inability of an impaired driver to divide his attention amongst the numerous tasks required to drive a car. For instance, to navigate a right hand turn, a drive must simultaneously be able to step on the brake, operate the turn signal, turn the steering wheel and then step on the gas while straightening out the steering wheel. An impaired driver would have difficulty appropriately dividing his attention between these tasks and may, for instance, forget about the brake and make the turn to fast. Impaired drivers are bad drivers because they cannot appropriately divide their attention in ways which we otherwise take for granted.

An officer is trained to look for cues of impairment in the other cars on the road. The officer should take note of an overly wide turn or a car that fails to stop at a stop light appropriately. If the officer notices a cue, he may follow the driver to observe further or pull the driver over. The driver’s reactions to being pulled over provides the officer with another opportunity to observe possible cues of impairment.

When the driver rolls down the window, the officer will meet with the driver and take note of the smell of alcohol, whether the driver’s eyes are glassy or bloodshot or whether the driver’s speech is slurred. The officer will then ask the driver to produce two documents, usually a driver’s license and proof of insurance.

The officer will ask the driver for two documents at the same time to see if the driver can divide his attention and look for both documents. Can the driver search for the driver’s license without forgetting about the insurance card? While the driver is retrieving these cards, the officer will ask the driver a question to further require the driver to divide his attention between the search for the cards and answering the question.

After the search, the officer may ask the driver an unusual question (e.g., what is your middle name?) to divide the driver’s attention mentally between answering the question and processing the unusual information. The officer may ask the driver to recite the alphabet beginning at some random letter (not A) and ending at another random letter (not Z). This again, requires the driver to divide his attention between reciting the alphabet and keeping the beginning and end points in mind. Finally, the officer may ask the driver to count the numbers between two random numbers (not multiples of 5 or 10), again requiring the driver to recite the numbers while keeping the start and end points in mind.

If the driver has difficulty dividing his attention, the officer will ask the driver to perform some standardized field sobriety tests. One test, called the horizontal gaze nystagmus test, looks for a special type of nystagmus in the driver’s eyes. A nystagmus is an involuntary jerking of the eyes. It cannot be controlled, nor can it be felt. Everyone exhibits some kind of nystagmus without knowing it in daily life. However, when a person has a high enough blood alcohol content, the person’s eyes will exhibit a special type of nystagmus that a sober person’s eyes will not. When the officer asks the driver to follow the officer’s finger with his eyes, the officer is checking for the horizontal gaze nystagmus which would indicate impairment. However, if the officer fails to perform this test correctly, the officer may cause other types of nystagmus to appear which are not indicative of impairment.

The other two tests are divided attention tests. In the walk and turn test, the driver must walk a certain amount of steps in a certain way, while keeping track of the number of steps, counting aloud the steps and remembering the instructions. In the one leg stand test, the driver is required to maintain his balance by standing on one leg while counting aloud beginning at 1001 (e.g. 1001, 1002, 1003, etc.).

These tests have been standardized and the officer is trained to note different ways a person may fail the test and score the test appropriately. These tests are only valid if they are performed and scored correctly.

After conducting the standardized field sobriety tests, the officer will ask the driver to submit to a preliminary breath test. This breath test may not be used as evidence of the driver’s blood alcohol content, but the officer will use it to determine whether to arrest the driver for DWI.

After the arrest, the officer will likely take the driver to jail to be booked. During the booking process, the officer will do some paperwork and may ask questions about what the driver had to eat and drink and when. The driver has the right to remain silent and should carefully consider exercising this right in a respectful manner. The officer will then ask the driver to submit to a breath test for the purpose of determining the driver’s blood alcohol content.

At Baker Legal Services we can review the officer’s report and any video of the investigation and arrest for any inconsistencies or potential defenses. We know what to look for to determine whether the officer may have made a mistake.