DUI evidence falls into five categories:
Field sobriety tests, commonly referred to by officers and California DUI lawyers as "FSTs", are simply a series of exercises designed in theory to test balance, coordination and divided attention (the ability to do two things at once). There are over a dozen such tests which have been used to varying degrees, the more common among them being one-leg-stand, walk-and-turn, nystagmus (following an object like a pen or finger from side-to-side with your eyes), the Rhomberg test (also called "modified position of attention"), hand-pat, finger-to-nose, fingers-to-thumb and alphabet recitation.
It is important to understand that these tests can be difficult for a sober person to "pass" (a subjective determination by the officer). In fact, the accuracy of field sobriety tests has been repeatedly challenged in scientific studies. And, contrary to popular belief, they are not legally required: You may decline to take them with no adverse legal consequences (other than perhaps angering the officer).
Studies funded by the National Highway Traffic Safety Administration have shown that only three of the field sobriety tests are effective in detecting a drunk driver: nystagmus, one-leg-stand and walk-and-turn. In other words, all other field sobriety tests are simply unreliable. Consequently, law enforcement agencies nationwide have been adopting the recommended "standardized" battery of three tests. Law enforcement agencies in California, however, have largely ignored the standardized FSTs and most continue to use whatever tests they prefer.
Field Sobriety Test
A description of the three so-called "standardized" field sobriety tests, developed by the National Highway Traffic Safety Administration — the heel-to-toe, one-leg-stand and nystagmus tests.
Standardized Field Sobriety Tests
More information on the NHTSA-approved battery of three "standardized" field sobriety tests.
Horizontal Gaze Nystagmus
The HGN test, or so-called "eye test", involves measuring the DUI suspect's eyes as he follows a moving object. This common field sobriety test is unreliable for a number of reasons, as shown by noted California DUI defense attorney Lawrence Taylor's horizontal gaze nystagmus cross-examination (see "Best DUI Lawyers").