If you have ever made a DWI/DUI arrest, chances are you have attended a NHTSA approved DWI Detection and Standardized Field Sobriety Test Practitioners Course. Some may have taken the course while attending the basic police academy, while others may have taken it as an in service course. No matter how or where you took the course, you are taught three tests to assist you in making the correct arrest decision. Horizontal Gaze Nystagmus commonly referred to as HGN, Walk and Turn and the One Leg Stand are the three standardized batteries of test that’s administered. Each of these had their own series of studies, both field and lab, to determine their accuracy. Let’s go back to the basics and take a look at each test individually.

HGN: HGN is defined as the involuntary jerking of the eyes, as the eyes move to the side. It is very important to remember the second part of the definition (as the eyes move to the side). Officers at times may mistake other forms of nystagmus for HGN due to the many different types of eye movements. There are 47 types of nystagmus, however officers are trained to recognize Gaze Nystagmus in particular Horizontal Gaze Nystagmus. We learn that nystagmus is an involuntary movement, and the subject is usually unaware the jerking is happening. So what causes HGN? Besides alcohol, Central Nervous System Depressants, Dissociative Anesthetics, and Inhalants all cause HGN.The 3 validated clues for this test are Lack of Smooth Pursuit, Distinct and Sustained Nystagmus at Maximum Deviation, and the Onset of Nystagmus Prior To 45 Degrees. Before we move further let’s pause because I know what you are saying. Yancy, there are 6 clues possible, and if I observe 4 of those 6 clues, that’s indicative of impairment. Guess what? You are correct! There are 6 clues possible but there are only 3 validated clues. Well how do I get to 6? I’m glad you asked. There are 3 validated clues. The subject you are testing has 2 eyes therefore you are looking for the clues in each eye. 3 validated clues times 2 eyes equal 6. 

Walk and Turn: The second test administered should be Walk and Turn. There are 8 validated clues possible however, only 2 clues need to be observed to indicate possible impairment. Over the years, I’ve heard officers say they can not remember the names of the clues. An acronym that is commonly used is BS SOWHAT. The BS is separate from SOWHAT because it represents the clues observed in the instruction stage; B-Balance (can’t maintain balance during instructions) and S-Starts to Soon. SOWHAT represents the clues during the walking stage. These clues are in no particular order. S-Stops Walking; Offline (steps offline) W-Wrong number of steps; H-Heel to Toe (miss touching heel to toe); A-Arms (uses arms for balance) T-Turns improperly. Two tips I have for the Walk and Turn test. Tip #1- most subjects stop walking just before the turnor immediately after the turn so be looking out for this easy clue. Tip #2- Ensure you put the subject in the start position and instruct them not to move until told to do so.Also ask the important question of “Do You Understand” prior to counting any clue in the instruction stage. A common mistake is officers will count the clue of starting to soon because the subject started to walk once they put their right foot in front of their left foot. If the subject was not told to wait for further instructions and starts walking, counting any clue during the instructional stage is improper. 

One Leg Stand- Instructions for this test are simple and short. Because of the simplicity of the instructions, Officers tend to over think them and turn simple instructions into something more difficult.  When it comes to the One Leg Stand, think of the acronym of PUSH. P-Puts foot down; U-Uses arms for balance; H-Hops. If two clues are observed, impairment is suspected. 

No matter what your experience is when it comes to impaired driving investigations, Standardized Field Sobriety Tests are important tools officers use to help determine impairment. Although the administration of SFST’s is a skill that can perish over time, with practice, officers will become more proficient and comfortable administering the 3 field sobriety test thereby saving lives by taking impaired drivers off the roadway.