Probable Cause, Traffic Stops, and DUI’s


You’re driving home after having a couple of drinks and a fancy dinner to celebrate a promotion, when the flicker of red and blue lights appears in your rear-view mirror. You know you didn’t drink that much but could you legally be driving under the influence? With nerves on edge, you pull over to the side of the road and wait for the officer to approach. Now what?


Is there probable cause?

Thanks to the 4th Amendment of the Constitution, which protects people from unlawful searches and seizures, a police officer can’t pull you over without a reason. He has to have probable cause to lawfully detain you. Probable cause is defined as a level of belief, based on facts, which could lead a person of “reasonable” intelligence to believe the suspect is guilty of committing a crime. A person can be pulled over for breaking a traffic law but not for suspicion of driving under the influence because the officer has no reason to suspect the driver of being guilty of DUI at this point in time.


Reasons for a traffic stop

A variety of reasons exist for a police officer to initiate a traffic stop. These include:

  • Swerving, also known as failure to stay in lane
  • Driving too fast or too slow
  • Failure to stop at stop signs
  • Failure to stop at traffic lights on red
  • Non-working headlights, tail lights or brake lights


During the traffic stop

The police officer is only allowed to detain you long enough to resolve the issue that caused the traffic stop. A lengthy stop without a valid reason could be considered unlawful detainment. During this time, there are numerous things the officer can request, such as:

  • Ask you to get out of your car
  • Ask for your driver’s license and do a driver's license check
  • Check to see if you have any warrants
  • Ask for information pertaining to vehicle ownership and automobile insurance
  • Look at visible areas in the vehicle, such as seats and floorboards
  • Ask to search non-visible areas of the vehicle
  • Ask questions about your condition, including asking if you’ve been on the road a long time, if you’ve taken any medications, or if you’ve had any alcohol to drink

Your answers, combined with the officer’s observations, can be used to establish probable cause for other infractions not related to the traffic stop so the officer could have a reason to suspect you of being guilty of DUI if your speech is slurred or your balance seems impaired and would have cause to question you in regards to this new suspicion.


Checking for DUI

If you’ve admitted to having a couple of drinks or the officer suspects that you’ve been drinking, a field sobriety test will probably be conducted. The test consists of:

  • Standing on one leg
  • Walking a predetermined distance, turning, and then walking back
  • Walking heel to toe
  • The Horizontal gaze nystagmus test, better known as the pen test, where the officer asks you to follow the tip of a pen with your eyes.

If the officer feels that you didn’t pass the field sobriety test, he may ask you take a Breathalyzer test to get a reading on your blood alcohol content (BAC). Based on the results of the field sobriety test and the BAC, the officer could come to the conclusion that you are guilty of DUI and arrest you.


Guilty of DUI?

You’ve been charged with DUI, but this doesn’t mean you’re guilty. Most of the evidence used was based solely on the opinion of the arresting officer, who could only base his opinion on the information gathered during the traffic stop. The field sobriety test hasn’t been updated in thirty years, and many people question their ability to pass the test even when sober. Consideration also has to be given to the circumstances surrounding the time and place the test was given, such as poor lighting or uneven ground. The results of the Breathalyzer test are also questionable and the results may be thrown out, depending on the condition of the machine and the paperwork regarding maintenance and operation history, as well as any records indicating the officer was trained to operate the device.

DUI is a serious offense and it shouldn’t be left to the opinion of one man. Know your rights regarding probable cause and the limitations of the sobriety tests so you don’t get arrested for not driving under the influence.


By Richard Jacobs

Share |