When a police officer suspects that a person is DUI or DWI, he will usually have the person get out of their car and perform a series of physical test. The three most common tests are the Horizontal Gaze Nystagmus test (HGN), the One Leg Stand test (OLS), and the Walk and Turn test (W&T). The officer may also ask a suspect to blow into a Portable Breath Test. These test are all completely voluntary. A person suspected of DUI does not have to perform any of the Field Sobriety Tests. These tests are used to provide evidence for a police officer to arrest the person for DUI and ask them to do a breath test back at the police station. Unfortunately, since most people have not spoken to a Maryland DUI lawyer about this prior to their contact with the police, they are not aware that they don't have to do the roadside test.

Police officers often tell people that the results of the Portable Breath Test can not be used against them in Court. This is essentially true, however, the officer is allowed to use the result of the PBT to decide whether or not they have probable cause to arrest the suspect. A person does not have to blow into a PBT. A suspect is not under any obligation to give the officer more evidence to make an arrest decision.

The official name of the roadside tests is Standardized Field Sobriety Tests. The word Standardized is extremely important. Standardized means that there is an official and correct way to administer the Field Sobriety Tests. The National Highway Traffic Safety Administration (NHTSA) publishes a manual and conducts training and certification courses for police officers in how to properly administer Standardized Field Sobriety Tests.

The police officer who is conducting the tests must do so in the proper manner, otherwise the test results are invalid and should not be considered as evidence of impairment. This is particularly important in cases where a suspect refuses to blow into the breathalyzer at the police station. If the State does not have a breath test, they must prove a Defendant's guilt using driving behavior, general demeanor, and the results of the Standardized Field Sobriety Tests. If the tests were not properly conducted their results should not be considered in deciding impairment. Having a Maryland DUI attorney who understands and is certified in Standardized Field Sobriety Tests can be the difference between Guilty and Not Guilty.