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4 Common Mistakes Made by Police in a DUI Case


During a DUI investigation, police officers are required to follow certain procedures to provide transparency, obtain evidence lawfully, and protect the rights of suspects. Unfortunately, it is not uncommon for law enforcement authorities to break these rules, typically by mistake.

If an officer made an error when investigating your DUI case, it is possible to file a motion to suppress evidence with the help of an experienced criminal defense attorney. If a judge grants this motion, the evidence from the DUI investigation cannot be used in court. Without key evidence to convict you of the crime, your case will most likely be entirely dismissed.

The following are the most common mistakes made by law enforcement in a DUI case:

  • Law enforcement failed to obtain reasonable suspicion – A police officer cannot make a traffic stop or detain a suspect without “reasonable suspicion,” which means a person either committed a traffic violation (e.g. speeding, changing lanes without using a turn signal, or driving with a broken taillight), appeared in need of help, or received a report of a vehicle matching the suspect’s description that was part of a crime. If the police pull you over without establishing reasonable suspicion, any evidence obtained after is considered inadmissible in court.
  • Law enforcement failed to establish probable cause – Before making an arrest, the police need probable cause. This means there is enough evidence of a DUI that a reasonable individual would believe a crime is being committed. If an officer doesn’t have probable cause, any evidence obtained cannot be used at trial.
  • Law enforcement failed to properly perform field sobriety tests – Field sobriety tests are used to determine if a person is intoxicated. Police officers must follow certain rules by the NHTSA, including providing an explanation of each test, performing them on level ground, and taking into consideration different factors such as age, health conditions, and fatigue. If an officer doesn’t administer a field sobriety test properly, the results cannot be used in trial.
  • Law enforcement failed to properly perform breath test – Police must also follow certain rules when administering a breathalyzer test, such as calibrating the device, observing a suspect for at least 15 minutes prior to taking the test, and properly storing test samples. If any error was made during the breath test, the results cannot be used in court.

If you have been arrested for a DUI offense in Chicago, IL, contact the Law Office of Steven Fine and schedule a free consultation today.