Probable Cause in a Missouri DWI/DUI Case

Law enforcement officers must be able to provide a specific reason for their initial stop of your vehicle along with any additional detention and investigation. Police cannot simply pull you over and investigate you for possible drunk driving without a valid reason (referred to as probable cause). There are specific legal standards that must be met. If these standards are not met, a skilled attorney can identify any violation of your constitutional rights and use the facts surrounding your case to effectively represent you in court.

Reasonable Suspicion for a Traffic Stop

The Standardized Field Sobriety Test (SFST) was developed in the 1970s by the National Highway Traffic Safety Administration (NHTSA) in order to provide law enforcement agencies with a standardized and empirically grounded way to determine whether drivers were intoxicated (leading to a DWI charge). The SFST is actually comprised of three distinct tests, which include:

  • The One Leg Stand
  • The Walk and Turn
  • Horizontal Gaze Nystagmus

The SFST is often used by police to gather evidence in support of their suspicion that a driver is impaired by alcohol or drugs. The results of field sobriety tests are not conclusive, however, and there are often ways to challenge them. For this reason, anyone that has been arrested after performing the field sobriety tests should have an attorney review their case immediately.

In order to legally pull you over, a police officer must have a reasonable suspicion that you have violated the law. This can be any law, such as speeding, not using a turn signal, or not coming to a complete stop. However, an officer can pull you over for a minor traffic violation and then later arrest you for DWI/DUI if there is probable cause for such an arrest.

Probable Cause to Investigate a Possible DWI

In 1981, NHTSA promulgated federal standards for field sobriety testing based on the results of research. The research determined that when the tests were conducted in a certain way, they could identify drivers who were intoxicated with a certain degree of probability. The standards developed by the agency dictate the way that the tests should administered as well as the signs of intoxication for which officers should look while the tests are being conducted.

When law enforcement officers deviate from these standards, it can result in unreliable evidence – and when evidence is unreliable, it can often be suppressed or excluded from your case. As a result, if your attorney can establish that NHTSA standards were not followed during your traffic stop, it can significantly weaken the prosecution’s case against you and achieve a better result, possibly leading to a reduced violation or dismissed case.

Once you are stopped, the officer must have a valid reason to begin an investigation for DWI. They cannot perform field sobriety tests or breathalyzer tests on everyone they pull over. Instead, they must have probable cause to believe that you have been drinking. Some observations that may support probable cause include:

  • Odor of alcohol on your breath
  • Slurring your speech
  • Watery, glassy, or bloodshot eyes
  • Disorientation
  • Alcohol containers in the car
  • Poor performance on field sobriety tests
  • A positive reading for alcohol on the officer’s preliminary breath test device
  • Signs of intoxication, such as stumbling, staggering or falling
  • A statement from you that you have been drinking or at a bar/party

In too many cases, police officers do not have adequate reasonable suspicion for a traffic stop and/or do not have probable cause for a DWI/DUI investigation or arrest. If these initial signs of impairment are not present, then legally the stop should end and you should be on your way with a ticket for the initial infraction. Unfortunately, that is not the way it always happens.

If your constitutional rights were violated, any evidence gathered in light of the violation should not be used against you, as it is illegal.This is why you need an experienced defense attorney to help you through this process.

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 DWI Defenses Against Field Sobriety Tests

Even in cases in which the SFST was performed in accordance with NHTSA standards, the evidence gathered can still be challenged. For example, nystagmus is a medical condition in which the eyes make repetitive involuntary movements. While it can certainly be caused by alcohol intoxication, it can also be caused by many other things as well, such as the flashing lights from a police car or having been in a serious car accident. Similarly, while people who have been drinking alcohol may demonstrate a lack of balance during the one leg stand, an ear infection or other physical ailment can also affect a person’s balance.

In addition to balance issues, other health problems an officer might mistake for intoxication include:

  • Diabetes – If a person with diabetes suffers from a sudden drop in blood sugar, their condition might mimic those of an intoxicated person. The person might have mild to severe symptoms and, if that person is put behind the wheel, they might appear to be swerving or driving drunk. Some symptoms may go so far as to include having a smell of acetone on the breath which an officer might mistake for them having been drinking since the smell of acetone (think nail polish remover) might smell like alcohol. This happens if a person’s ketones are at unsafe levels, putting them at risk for diabetic ketoacidosis (DKA) which causes the acetone smell.
  • Epilepsy – A person who suffers from epilepsy and is not managing it well, of suffers from a sudden seizure, might appear to be driving while intoxicated. Seizures might be partial or generalized and come with a number of symptoms that could mimic intoxication.
  • Traumatic brain injury (TBI) – A person who has suffered from a concussion or hematoma (bleeding on the brain) might behave like someone who is under the influence of a substance. However, their condition is quite severe and requires immediate medical attention. If an officer comes upon a car accident and a driver in the accident is behaving erratically such as the driver lacks the ability to focus, has hand-eye coordination difficulties, or is unable to make simple movements, they might mistake the symptoms of TBI for drunkenness.

These are just a few examples of ways in which symptoms caused by other conditions could be mistaken for signs of impairment. DWI defenses are not readily apparent to the untrained eye, so it is imperative for anyone facing a DWI case to speak to an attorney as soon as possible.

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Contact a St. Louis DWI Attorney

Our skilled St. Louis criminal defense attorneys will fight to have any unlawful evidence against you thrown out of court, which often results in having your charges dropped. We fight for your rights in DUI cases, so please contact Muhlenkamp & Bernsen today to discuss your case.

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