Observing an Impaired Driving Enforcement Training

By Member T. Bella Dinh-Zarr, PhD, MPH

This summer, I had the opportunity to observe men and women training to be law enforcement officers. Part of their training included 40 hours focused specifically on executing a standardized field sobriety test (SFST).

The SFST is a series of assessments an officer performs during a traffic stop to determine if a driver is impaired. I was surprised to learn how the SFST also helps officers detect drivers who are impaired by drugs other than alcohol.  When an officer encounters a subject who he believes to be impaired, his first response will be to evaluate his physical condition by administering a SFST.  Although all the clues for impairment which are analyzed in the SFST are for alcohol, there are similarities in impairment by some of the 7 different drug classes.  Additionally, the presence of some impairment clues and the absence of others can be a strong indicator of drug impairment.  For instance, a subject who displays nystagmus (uncontrollable twitching of the eyes) from alcohol impairment will also present an inability to maintain balance.  With some drug classes, there will be a high degree of nystagmus, but their balance may not be affected to the same degree.  The same goes with the strong odor of alcohol.  If a subject is obviously impaired but has no odor of alcohol about their breath, drug impairment may have an influence.  When officers administer an SFST to a suspected drug-impaired driver, the results often identify the need for a drug recognition expert (DRE) to evaluate the driver for physical signs of drug impairment.

Trainees learn about the effects of alcohol on the body and the visual cues to look for when they suspect a driver is impaired, as well as how to determine the likelihood of impairment so they have probable cause to administer an impairment test. In addition to the SFST training, officers spend hours learning how to document impaired driving arrests and how to present evidence of such arrests in court.

To effectively practice these skills, trainees conduct the SFST on live subjects who have consumed varying amounts of alcohol in a controlled environment (a law-enforcement training facility; subjects are driven home by law enforcement officers afterward). Volunteers are given measured amounts of alcohol over the course of 4 hours prior to the mock SFST, and then are given a breath test to document their breath alcohol concentration (BrAC) as the evaluation begins. SFST instructors observe trainees as they evaluate subjects and offer real-time feedback and suggestions for improvement. By using live subjects, trainees witness how variably alcohol consumption can present in individuals.

A law enforcement trainee conducts the SFST on a live subject that has consumed alcohol.
A law enforcement trainee conducts the SFST on a live subject that has consumed alcohol

I spent some time with the live subjects, all of whom were impaired, before their evaluations. All subjects had a BrAC of 0.08 percent or higher and, had they been behind the wheel, would have been subject to arrest. The SFST instructor showed me the documented BAC levels of the subjects. While all of the subjects were at or above 0.08, they were each keenly aware that they were in no condition to drive. They were unsteady on their feet, reacted slowly to orders, and struggled to follow directions given by the trainees. I couldn’t tell which subjects had higher BACs than others, but just knowing that some were close to or just above the “legal limit,” I would not be comfortable sharing the road with any of them.

When the evaluations started, I got to be one of the (sober) subjects evaluated by the trainees. I received the same set of questions and was given the same tests as the impaired subjects. The SFST is incredibly thorough, and officers determine the likelihood of impairment by scoring the elements of the test based on how the subject performs. I was asked questions such as, “Where are you coming from?” “Have you had anything to drink tonight?” “Are you on any medications or do you have any medical conditions that I should be aware of?” From there, I was asked to walk a certain number of steps, heel to toe, counting each step out loud; to stand on one foot with my arms at my sides and balance, and to track a pen that the trainee moved in front of my face from side to side. The test is designed to evaluate a person’s ability to complete simultaneous tasks—an ability that is hindered by impairment. What I learned later is that each part of the test helps the officer gather data about the subject—slurred speech, an alcohol odor, impaired coordination, and atypical eye movement are all signs of impairment. Subjects who score in or above a certain range on the test are considered to have a positive likelihood of impairment.

Member Dinh-Zarr undergoes the SFST
Member Dinh-Zarr undergoes the SFST

I learned two things through this test. First, I struggle with balancing on one foot, even when I’m sober! Second, the trainees are taught this protocol very thoroughly; they are instructed to take their time and not rush any element of the test. They need to be very deliberate because officers cannot administer a breath test unless they positively detect impairment.

End Alcohol and Other Drug Impairment in Transportation is on our Most Wanted List of transportation safety improvements. Specifically, we recommend that all states lower their per se BAC limit from 0.08 percent to 0.05 percent or lower. Observing this SFST training exercise reaffirms my belief in the NTSB’s position on this recommendation. A 0.08 percent BAC illegal limit is far too high. At .05, drivers have difficulty with vision, coordination, and steering, even if they may not realize it.  In fact, in 2016, approximately 1,400 people were killed by drivers with a BAC of 0.01­–0.07 percent.

.01 - .07 BAC Fatalities
Driver BAC’s from fatal crashes in 2016. Drivers are not considered legally impaired before 0.08 BAC, but 1,400 people were killed by drivers that had between 0.01 and 0.07 BAC in 2016.

In addition to calling on states to lower their legal BAC limit, we also recommend increased high-visibility enforcement, such as sobriety checkpoints, which allow law enforcement officers to screen a high number of drivers in a short amount of time for potential impairment. All of these safety recommendations are not intended to increase arrests.  In fact. they may decrease the number of arrests because they deter many impaired people from even getting behind the wheel in the first place.  That is true prevention!

Our 2013 report, “Reaching Zero: Actions to Eliminate Alcohol-Impaired Driving” includes a series of recommendations to combat impaired driving. We believe that implementing a combination of a lower BAC legal limit, increased or high-visibility enforcement, and mandatory ignition interlock devices for all DUI offenders can reduce the number of impaired drivers on our roadways. Our goal is to eliminate impaired driving by convincing people to separate drinking or drugging from driving.

I’d like to thank all law enforcement officers who conduct SFSTs and remove alcohol-impaired drivers from our roadways. It may not seem as glamourous as other aspects of their job, but they are making our nation safer with this important work. These trained professionals help keep our roads safe and prevent families from losing a loved one to an impaired driving crash. It’s up to the rest of us to do our part to reach zero.

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