The central issue in almost every DWI or DUI case is whether your blood alcohol content (BAC) is equal to or greater than the statutory minimum. In other words, if your blood alcohol content is above this minimum, you are presumed to be legally intoxicated and subject to being charged with DUI / DWI.

In some states, the drunk driving laws differentiate between a DUI and a DWI, and the DUI is considered a "lesser" violation in comparison. In these states, a DUI usually signifies a lesser intoxication to some extent, which is determined by a person’s blood alcohol level at the time of arrest.

The Commonwealth of Virginia does not recognize any difference between a DUI and a DWI. As far as Virginia laws are concerned, any blood alcohol level over the specified limit is a crime that will be punished consistently.

Field sobriety tests (FST) are agility tests that are used by law enforcement to determine if a person is impaired by drugs and/or alcohol.  If a person is believed to have been driving while under the influence, law enforcement may request that the person perform a series of field sobriety tests before deciding to make a DWI/DUI arrest.   

Up until the mid 1970s, most police departments used various types of field sobriety tests when enforcing drunk driving laws. At that time, when someone was stopped, there was very little in the way of standardization when it came to the tests administered during drunk driving arrests. Because of the lack of regularity, the National Highway Traffic Safety Administration (NHTSA) set out to identify the best tests for enforcement along with a means of standardization.

Sobriety checkpoints, or roadblocks, are temporary installations used by law enforcement to catch drivers who are under the influence of alcohol. This approach was modeled on the success of roadside safety checks and license and registration inspections.