As a licensed driver in Massachusetts, you are expected to abide by certain rules and take responsibility for your actions. However, law enforcement also has rules and procedures to follow of their own. One of the most important is known as probable cause to stop a vehicle, detain a person and then arrest them.

Before a police officer can legally stop your vehicle, they must have observed you violating some sort of traffic law such as speeding or swerving all over the road. Often there are witnesses who may tip police off to someone who is driving carelessly on the road. The police officer cannot stop you on the witness' claims alone. They must first observe you violating some law.

Once the officer stops you and approaches you, they cannot start searching your car or self without having probable cause. For example, if you were initially stopped because you had a tail light out, the officer cannot start searching your car for open alcohol containers or drugs unless they have a reason to believe you would have these substances.

There are even situations where a person's race has influenced how an officer treats them. Prejudice can be a possible defense when it comes to your OUI case.

If the officer smells alcohol on your breath or has other probable cause to believe that you had been drinking, they will ask you to take a breath test and/or field sobriety testing. This is known as the detaining process. This means that the officer had a reason to keep you longer than the reason for the initial traffic stop of having your tail light out.

During the field sobriety tests, the officer will score your performance. According to their scoring procedures, you must fail your field sobriety test before the officer can arrest you for OUI. They cannot arrest you for OUI without probable cause from your field sobriety test.

How can probable cause affect my OUI case?

Depending on the facts of your case, the state must prove that they had probable cause to stop, detain and arrest you for OUI. If they cannot prove all of these, then some or all of the evidence the state obtained against you can be suppressed in court.