A Virginia highway patrol officer may stop a vehicle after observing a motorist violating a traffic law. If a vehicle has a broken taillight or its driver runs a stop sign, an officer may initiate a traffic stop to issue a citation.

Once stopped, an officer may ask a motorist some questions. Signs of impairment may raise suspicions of DUI and lead up to a breath test.

What are some signs of impairment that could lead to an initial field sobriety test?

Slurred speech or a strong odor of alcohol may cause an officer to ask a driver to step out of the vehicle and stand on one leg. By applying for and obtaining a Virginia driver’s license, motorists agree to perform a field sobriety test when requested. An officer, however, must have a reason to ask a driver to do so.

For example, an officer stopped a motorist for driving with high beams on and then noticed several empty alcoholic beverage cans. As reported by the Virginia Gazette, the driver smelled of alcohol and had red, glassy eyes. Because the officer had reason to suspect driver intoxication, he asked him to perform a field sobriety test, which he failed.

What could happen if a motorist fails a portable breath test?

If an individual fails a field sobriety test, an officer may ask the driver to blow into a portable breath testing device. The device measures a motorist’s blood-alcohol content level from a breath sample. According to WebMD, some devices may, however, produce unreliable results due to factors such as an individual’s gender or weight.

A reading showing a BAC level of 0.08% or more typically results in an officer placing a motorist under arrest for DUI. A prosecutor, however, may not convince a court to convict unless there exists substantial evidence to prove impairment.