An American's constitutional rights are never more vulnerable than when they drive. The roadway is the most common place a person will be accused of breaking a law during their lifetime. When that person is accused of committing a criminal act while driving their constitutional rights are at risk of being violated by an undertrained or unethical police officer. Such a violation can result in the charges being dismissed or evidence suppressed. While some people speak of "technicalities" that get people out of trouble, I speak of the Constitution.
The first question I ask is why was the person stopped? To justify a stop the State must prove that there was reasonable suspicion that the driver committed a traffic violation or was otherwise committing a crime. I have had many cases dismissed because the State could not prove that the officer had a reason to contact the driver.
Miranda violations also frequently occur during a DUI investigation. A defendant should never answer the officers questions. The officer has to inform the defendant that they have the right to remain silent once they are placed under arrest but answers given to the officer before the arrest are are often very harmful to the defense. My advice is that when an officer asks a question that could be incriminating at all (like "have you been drinking?) a person should reply, "I am not comfortable answering your questions without an attorney." My business card has a written notice to the officer that the driver has invoked his or her right to remain silent which should be handed to the officer along with the driver's license, insurance, and registration.
The next constitutional issue that can arise during a DUI investigation is probable cause to arrest. Did the officer have the facts to prove that the defendant was driving under the influence when he decided to arrest. There are many factors to be considered including the reason for the stop, signs of alcohol or drug ingestion, performance on field sobriety tests and admissions made by the defendant to name a few. Sometimes the police don't have enough proof that the defendant was even driving the car when they make the arrest. If you are wondering if you are under arrest during an investigation simply ask if you are free to leave because you are ready to go. That question usually forces the officer to make a determination as to whether or not there is probable cause to arrest.
A big issue in DUI cases is the right to an attorney. A person under arrest has the absolute right to an attorney and the officer needs to take reasonable steps to give a defendant that opportunity. Officers are often under-trained with respect to this issue and can, therefore, make mistakes that result in the violation of a defendant's constitutional rights. The remedy for a right to counsel violation can be a dismissal of the case or the suppression of evidence depending on the circumstances. Either way the defendant is in a much better position.
There are many other "technicalities" that could result in a good outcome for a defendant. My favorites come from the Constitution. When it comes to constitutional rights a vehicle really is where the rubber meets the road.