Field sobriety tests

The officer will administer one or more field sobriety tests (FSTs). FSTs are "divided attention tests" that theoretically test the suspect's ability to perform the type of mental and physical multitasking that is required to operate an automobile. The most commonly administered FSTs include:

*horizontal gaze nystagmus test, which involves following an object with the eyes (such as a pen) to determine characteristic eye movement reaction. A sober person should be able to smoothly track the object with their eyes. In an intoxicated individual the eyes will jerk as they follow the object.
*walk-and-turn (heel-to-toe in a straight line).
*one-leg-stand.
*modified-position-of-attention (feet together, head back, eyes closed for thirty seconds; also known as the Romberg test).
*finger-to-nose (tip head back, eyes closed, touch the tip of nose with tip of index finger).
*recite all or part of the alphabet (a common myth is that the alphabet must be recited backwards, however, this is never done during an FST, as many sober people are unable to do this.).
*touch each finger of hand to thumb counting with each touch (1, 2, 3, 4, 4, 3, 2, 1).
*count backwards from a number such as 30 or 100.
*breathe into a "portable or preliminary breath tester" or PBT.

Although most law enforcement agencies continue to use a variety of these FSTs, increasingly a 3-test battery of standardized field sobriety tests (SFSTs) is being adopted. These tests are recommended by the National Highway Traffic Safety Administration (NHTSA) after studies indicated other FSTs were relatively unreliable. The NHTSA-approved battery of tests consists of the horizontal gaze nystagmus test, the walk-and-turn test, and the one-leg-stand. In some states, such as Ohio, only the standardized tests will be admitted into evidence, provided they were administered and objectively scored "in substantial compliance" with NHTSA standards (ORC 4511.19(D)(4)(b)).

FSTs are more effective at determining the level of impairment than they are at estimating the driver's blood alcohol concentration (BAC). However, studies question whether the tests increase the officer's ability to judge either. In 1991, Dr. Spurgeon Cole of Clemson University conducted a study on the accuracy of FSTs. His staff videotaped individuals performing six common field sobriety tests, then showed the tapes to 14 police officers and asked them to decide whether the suspects had "had too much to drink and drive". The blood-alcohol concentration of each of the 21 DUI subjects was .00, unknown to the officers. The result: the officers gave their opinion that 46% of these innocent people were too drunk to be able drive. This study showed the possible inaccuracy of FSTs. Cole and Nowaczyk, "Field Sobriety Tests: Are they Designed for Failure?", 79 Perceptual and Motor Skills Journal 99 (1994).

An increasingly used field sobriety test involves having the suspect breathe into a small, handheld breath testing device. Called variously a PAS ("preliminary alcohol screening") or PBT ("preliminary breath test"), the units are small, inexpensive versions of their larger, more sophisticated instruments at the police stations, the EBTs ("evidentiary breath test"). Whereas the EBTs usually employ infrared spectroscopy, the PAS units use a relatively simple electrochemical (fuel cell) technology. Their purpose, along with other FSTs, is to assist the officer in determining probable cause for arrest. Although because of their relative inaccuracy they were never intended to be used in court for proving actual blood-alcohol concentration, some courts have begun to admit them as evidence of BAC.