When it comes to evaluating a person's level of intoxication, many Pennsylvanians think of the blood or breath-based tests that law enforcement officials may administer to learn of a person's blood alcohol concentration. A person's blood alcohol concentration, often shortened to BAC, is a number that indicates the amount of alcohol that is in a person's body. State laws are written with BAC in mind and with intoxicated driving charges generally applying when a driver's BAC reaches or exceeds .08.
However, there are other evaluative tools that law enforcement officials may use to determine if drivers are under the influence. Those tests do not use materials from the suspects' bodies, but rather the suspects' bodies themselves for evaluation. They are called field sobriety tests and they are used to check drivers' coordination, balance and capacity to follow instructions.
For example, the walk and turn test is a common field sobriety test that law enforcement officials administer. In it, a person is asked to walk toe-to-heel in a straight line and then return the same way. If the person falters or loses their balance, fails to keep their steps regulated or simply cannot do it, a law enforcement officer may find evidence of their intoxication.
Other common tests like the one-leg stand and the horizontal gaze nystagmus also test drivers' control over their bodies. However, a driver's failure to successfully pass one or more of these tests does not mean that they are necessarily under the influence of alcohol. If a driver is charged with a drunk driving crime based on evidence collected from a field sobriety test, they may wish to discuss the conditions and circumstances under which the tests were administered with a drunk driving defense attorney.