DUI Investigations and Considerations

Police officers score unofficial points for writing traffic tickets, but they get extra credit for making DUI arrests. They are always on the lookout for “suspicious” driving behavior (such as weaving or other erratic driving) that will allow them to stop a vehicle to conduct a DUI investigation. They are particularly vigilant near “bar time” because they assume that drivers who are on their way home from a tavern are probably DUI.

How do the police investigate those suspicions after they turn on their red and blue lights to stop a driver? They need to turn a suspicion into probable cause before they can make a DUI arrest. Here are some ways the police go about doing that.

The traffic stop

If a driver ignores the red and blue lights, the police will assume that the driver is too drunk to notice flashing lights in the rearview mirror. The longer it takes the driver to stop, the more likely it is that the police will use that delay as evidence of impairment. On the other hand, if the driver slams on the brakes as soon as the lights come on, the driver’s poor judgment will be seen as proof that the driver is DUI.

When the driver pulls over to the side of the road, how the driver parks can contribute to probable cause. A driver who stops three feet from the curb on a city street, or halfway off the shoulder on a highway, is giving the police reason to believe that the driver is under the influence.

The initial contact with the driver

When the police first approach the driver (usually after sitting in the squad car for a few minutes to let the driver sweat), they expect a sober driver to have the window down and a driver’s license in hand. If they have to knock on the window to get the driver’s attention, they will add that to the list of factors that support probable cause to make a DUI arrest. If the driver is not ready to produce a driver’s license, the officer will watch to see whether the driver fumbles in a wallet or purse and has trouble finding or removing the license. If the driver hands the officer something other than a license (such as a Sam’s Club membership card), the officer will probably decide on the spot that the driver is guilty of DUI.

Officers are trained to look for three things when they first encounter the driver:

  • the odor of an intoxicant
  • slurred speech
  • “glassy” eyes

Police officers routinely state in police reports that all three of those were present. They consider the combination of all three to be strong evidence of DUI.

Before running the license, the officer will usually ask “Have you been drinking?” The most common answer is “I only had two beers.” The police hear that answer so often that they never believe it. A better answer is, “My lawyer told me I should never answer a police officer’s questions unless my lawyer is with me.”

You should be polite and respectful as you speak to the officer, because a belligerent attitude is viewed as evidence of intoxication. Telling a lie both contributes to probable cause (if it is obvious that you are lying about, for instance, having consumed no alcohol) and subjects you to an arrest for obstructing the officer’s investigation.

Outside of your vehicle

If you have not been drinking, it may be clear to the officer that you are not guilty of DUI. The officer will run your license and, assuming you do not have outstanding warrants, will return the license and let you go (along with a traffic ticket if the officer stopped you because you violated a traffic law).

If the officer believes you were drinking, the officer will ask you to exit your vehicle. If you stumble as you get out of the car, or hold the door for balance, the officer will deem your actions to be additional evidence of DUI. If you stagger as you walk, that too will be added to the list of suspicious behavior.

Assuming that all of those factors add up to a reasonable suspicion that you are under the influence, the officer will conduct field sobriety tests. The officer may also ask you to blow in a portable breath testing device. If you do, the test result may be the strongest evidence upon which a probable cause determination is based. Otherwise, the officer will decide whether all of the his or her observations, including your field sobriety test performance, add up to probable cause to support a DUI arrest.