Common Mistakes Made by Law Enforcement in a DUI Case

Despite certain procedures police officers must follow during a DUI investigation, they often still make mistakes. These protocols are designed to protect the rights of individuals who have been stopped, provide transparency throughout the traffic stop, and lawfully collect evidence.

Common Mistakes Made by Law Enforcement in a DUI CaseIf law enforcement officials intentionally or unintentionally break these rules, any evidence gathered during the DUI investigation cannot be used by the prosecution in court. A criminal defense attorney can help the defendant file a “motion to suppress” to throw out any evidence that was illegally obtained.

The following are the most common errors police offices make in a DUI case:

  • Invalid traffic stop – Police officers must establish “reasonable suspicion” to pull someone over. Common examples include traffic and equipment violations, such as speeding or driving with a broken taillight. Law enforcement cannot simply pull over someone for having a hunch or gut feeling.
  • Improper breath test – The police use roadside breathalyzers to determine a driver’s blood alcohol content (BAC) levels. Before administering the test, officers must observe a suspect for at least 15 minutes to ensure he/she doesn’t vomit, burp, or otherwise skew the results of the breath test. Additionally, they must properly calibrate the testing device before use. If the officer doesn’t conduct the 15-minute observation or the breathalyzer wasn’t properly calibrated, the results cannot be used at trial.
  • Improper field sobriety test – Officers must properly understand, administer, and evaluate field sobriety tests to use the results against a DUI suspect. Furthermore, they must take into consideration certain factors that may influence the results, such as a suspect’s pre-existing injuries and medical conditions, road conditions, and weather conditions. Failure to adequately administer or review a suspect’s performance on a field sobriety test means the results are invalid.
  • Lack of probable cause – In order to place a DUI suspect under arrest, police must establish probable cause. If law enforcement doesn’t have probable cause, any evidence gathered during the investigation cannot be used in court.

Without strong pieces of evidence against the defendant, the judge can dismiss the entire case.

If you have been arrested for a DUI in West Virginia, contact The Wagner Law Firm today at (304) 461-6000 to request a free case review.

Harley Wagner Avatar

Harley Wagner

Attorney Thomas M. Cooley School of Law, National College for DUI Defense, West Virginia State Bar

Harley has represented over 3,000 citizens throughout West Virginia. He is the author of West Virginia DUI Defense, The Law and Practice, which is the go to handbook for many magistrates, judges, defense attorneys, prosecutors, and law enforcement throughout West Virginia. has been selected for inclusion in West Virginia Super Lawyers® eight times.

He maintains an AV Preeminent® Rating by with Martindale-Hubbell®, an Avvo Rating of 10.0, and an excellent annual rating from the Better Business Bureau.

Harley is also the past president of the national DUI Defense Lawyers Association (2020-2021) which he was Charter Member and founder of in 2014

Areas of Expertise: DUI Defense, Aggravated DUI, Alternative Sentencing, Boating Under the Influence, Commercial License DUI, DMV Hearings, DUI Drugs, DUI with Injury, DUI Causing Death, Out-of-State Resident DUI, DUI Immigration Consequences, DUI with Minor in Vehicle, DUI Child Endangerment, Fleeing a DUI, Felony DUI, Permitting DUI, Underage DUI, Multiple DUI, First-Offense DUI, Second-Offense DUI, Third-Offense DUI, DUI Testing, Field Sobriety Tests, Breathalyzer, Blood Testing, DUI Info Center, College Student DUI, DUI Checkpoints, DUI Court Dates, DUI Deferral Program, Implied Consent, Test & Lock Program, FAQ, DUI Penalties, Administrative License Revocation, Ignition Interlock Device, License Suspension