When can the Police Lawfully Stop your car to investigate a Driving under the Influence offense?


There are several ways you can be forced into an unwanted contact with the police. Probably the most common one is the claim by police that you committed some traffic offense. In the context of driving under the influence police often claim you were weaving within a lane, or crossing over a lane marker, or going to too slow, or going too fast, but it can be anything. Often the police will not give you any reason. No matter what the reason for stopping your car it must comply with certain basic requirements. It cannot be a random stop based on curiosity or a hunch; rather it must be based on a recognized legal standard. That standard is stated thusly, there must be a “reasonable suspicion” that you have committed, or are committing some offense, either traffic or criminal, to justify a police stop. A reasonable suspicion is more than a mere suspicion rather it requires specific and clearly expressed facts that enable a police officer to form a rational belief a criminal or traffic offense is being committed or has been committed.

Cop investigating DUI offense

You may ask what does this have to do with defending a charge of driving under the influence. Actually, it is very important. The reason for the requirement to justify a traffic stop is an important one and it is based in constitutional law. The 4th amendment to the United States Constitution prohibits police from making unreasonable searches and seizures. Most have heard of this prohibition, although few know how it works in practice. Cases decided by the United States Supreme Court as well as lesser courts have defined what it means to conduct an unreasonable search and seizure and the consequences that ensue when police fail to comply with the 4th amendment prohibitions.

You may also ask what a traffic violation and police stops have to do with searches and seizures? Courts have held stopping a car is a “seizure” of the driver of that car within the meaning of the 4th amendment and therefor it must be reasonable. The standard for reasonableness for car stops is, as mentioned above, a reasonable suspicion of illegal conduct by the driver of that car. What is unreasonable varies from case to case and will depend on the facts of your particular case. Whether an issue is present is for an experienced attorney to determine.

Cop Investigating DUI offense

Another question you may ask is what does this mean to me if the police did act in violation of the constitutional standard? It could mean a lot. If after a careful evaluation of the facts of your case, including your description of what happened, an examination of the facts stated by the police officer in the police report, and any witnesses statements, I determine there was not sufficient reasonable suspicion to make a traffic stop, we can then file a motion to suppress. A motion to suppress is based on section 1538.5 of the California Penal Code, and the California and United States Constitutions. If the motion is successful, all evidence acquired as a result of the illegal stop cannot be used against you in court. This is what is called the exclusionary rule and it was formulated by the Supreme Court to punish police for violating a person’s 4th amendment rights. The evidence acquired includes all symptoms of impairment the police note after you were illegally stopped. Usually the police claim that after the stop you exhibited poor balance, bloodshot eyes, the smell of alcohol, slurred speech . . . etc. Very importantly, the results of any chemical tests of your blood alcohol level are excluded from evidence. What then happens is the prosecution has no evidence other than the fact you were driving and they will usually be unable to proceed and the case will be dismissed.