Important Facts About Standardized Field Sobriety Tests 

Officers must adhere to Standardized Field Sobriety Test (SFST) protocols. Mistakes can be made in the Officer’s reading instructions, interpreting clues, counting single clues more than once, modifying the tests and testing inappropriate subjects. When mistakes are made, evidence of these mistakes may be used to invalidate the test results in a court of law.

Below are some important facts to consider if you are facing DUI charges:

There are three SFSTs:  Horizontal Gaze Nystagmus (HGN), the Walk-and-Turn (W&T) Test (known by many names, i.e. “walking the line”), and the One-Leg Stand (OLS) test.

  • HGN – the Officer (who should be certified in its administration) first checks for Equal Pupil Size and Equal Tracking. If either is not present, it could indicate recent head trauma or other neurological disorder or presence of some types of drugs. Then, in three separate tests, he checks for smooth pursuit; onset of distinct and sustained nystagmus (involuntary jerking of the eyes) at maximum deviation – minimum of four seconds; and onset of nystagmus prior to 45-degree angle. The Officer can mess up this test in a number of ways. He can have the stimulus (penlight or finger) too close to the eyes (15” preferred) or too high or low (slightly above eye-level is proper location). He should start his test at the bridge of the nose and take two seconds to go to far left, then four seconds to go to far right, repeat left and right in four more seconds, then back to bridge of nose in two seconds. These two complete passes, with two second stops at each extreme, should be repeated twice for each of the three separate tests. Each test, each eye is a possible clue. Maximum number of clues possible is six. Four or more clues is a fail.
  • W&T – the Officer puts the Defendant in an awkward stance with heel-to-toe on line while reading directions; clues include stepping off line or starting test before being told to do so (single clue); failure to touch heel-to-toe; step off line; wrong number of steps; incorrect turn; raising arms more than 6” from body and sway. Any of these violations, regardless of how many times committed count as a single clue. 
  • OLS – Stand feet together, arms at side. Lift leg of your choice 6” off ground and hold it there until told to put it down. At same time, count 1-1000, 2-1000, etc. Test to be performed for 30 seconds. Clues:  Starting early, putting foot down more than twice, sway, hands raised more than 6” from sides, incorrect counting, stopping early. 

If the Officer misinterprets a clue or counts it more than once, that is an error in protocol. If the Officer administers the W&T or OLS to persons aged 65 or over or more than 50 pounds overweight (not suitable candidates), those factors invalidate the reliability of the tests likewise. These are ways to attack the findings of the Officer concerning the tests, which are designed, when administered in strict accordance with the protocols of the training manual, to provide a strong likelihood that the driver is 0.08% or higher.  

These findings are just a portion of evidence the Officer can gather to determine whether probable cause exists to arrest the driver and require him to submit to an evidentiary test of his blood or breath. If the Officer’s findings are flawed, it takes away from potential probable cause to justify the arrest. Other factors the Officer can consider in determining whether this probable cause exists are driving pattern, physical observations (slurred speech, watery eyes, staggering, odor of alcohol, etc) and the result of a Preliminary Breath Test (PBT). 

The PBT result cannot be used to prove the level of alcohol in the driver at the time of driving, but can be used in support of whether there is sufficient probable cause to arrest and require the Evidentiary Test (EBT) – which takes the form of either a breath test at the station or a blood draw and test. The PBT must be calibrated monthly and have comprehensive maintenance annually.

If there is insufficient probable cause to arrest based upon scant physical observations, flawed SFSTs and/or an improperly maintained PBT, then a Motion to Suppress can be filed by the Defense Counsel alleging an Unlawful Arrest (Seizure) in violation of the U.S. and Nevada Constitutions. If the Motion is granted, then all evidence gathered after the arrest (the EBT) is suppressed. Likewise, if the Officer’s initial encounter with the Defendant is the product of an unlawful seizure (i.e. no probable cause to stop a vehicle because no traffic violation was observed and there was insufficient facts possessed by the Officer at the time of the stop to justify a reasonable Officer’s belief that criminal activity was afoot, had or was about to occur) then all evidence following the initial stop of the vehicle would be suppressed.