Field Sobriety Tests
NHTSA - Standardized Field Sobriety Tests
The Standardized Field Sobriety Testing (SFST) battery is composed of
three tests: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn (WAT), and
One-Leg Stand (OLS). The tests were developed by the National Highway
Traffic Safety Administration (NHTSA) in the late 1970's. In 1981, law
enforcement officers began using the SFST battery during roadside encounters
with motorists to determine whether drivers were intoxicated. The
SFTST are alleged to enable ordinary police officers to determine whether a
person's blood alcohol content (BAC) is .10 or above. Most states
including Texas have revised drunk driving laws that define DWI at a BAC of
.08 or above.
The validity of SFST results requires that the officer following the
established, standardized procedures for test administration and scoring.
According to NHTSA when properly administered and scored, the accuracy of
the SFSTs in correctly identifying intoxicated drivers is as follows:
· HGN - 77%
· WAT - 68%
· OLS - 65%
This means that even under laboratory conditions, the HGN was wrong 23%
of the time, the WAT 32% and the OLS 35% of the time. Additionally,
NHTSA's own research emphasizes that test results are valid only when
administered in strict compliance with NHTSA protocol. If
anyone of the standardized field sobriety elements is changed, the validity
is compromised. It is therefore imperative that a NHTSA trained and
qualified attorney review SFST administration. It may be possible to
suppress the results of an improperly administered test.
Horizontal Gaze Nystagmus (HGN)
"Nystagmus" is an involuntary jerking of the eyes. HGN refers to an
involuntary jerking occurring as the eyes gaze toward the side.
Persons exhibiting nystagmus are unaware that the jerking is happening.
The theory behind the test is that nystagmus becomes visible to the naked
eye when a person's alcohol concentration is .10 or above.
In administering the test the officer has the subject follow the motion
of a stimulus with the eyes only. The stimulus may be the tip of a pen
or penlight, an eraser on a pencil or a fingertip. As the eyes move
from side to side each eye is examined for three specific clues:
- Lack
of Smooth Pursuit - does the eye move in a smooth manner or or does
it jerk from side to side
-
Distinct & Sustained Nystagmus at Maximum Deviation - when the eye
moves as far to the side as possible and is kept at that position
for several seconds, does it jerk distinctly
-
Onset of Nystagmus Prior to 45% - as the eye moves to the
side, does it start to jerk prior to a 45% angle
Walk and Turn
The WAT is a divided attention test consisting of two stages: Instruction
Stage; and Walking Stage. In the instruction stage, the subject must
stand with their feet in heel-to-toe position, keep their arms at their
sides, and listen to instructions. The subject must maintain the
heel-to-toe position and may not begin walking until all instructions are
given. In the Walking Stage the subject takes nine heel-to-toe steps,
turns in a prescribed manner, and takes nine heel-to-toe steps back, while
counting out loud and watching their feet. Officers observe the
subject's performance for eight clues:
-
can't balance during instructions
-
starts too soon
stops while walking
misses
heel to toe
steps off line
uses arms for balance
improper turn; and
wrong number of steps
A subject who exhibits two or more clues will fail the test and be
classified as having an alcohol concentration of .10 or above. Scoring
is entirely subjective and within the officer's discretion.
One Leg Stand (OLS)
The OLS is also divided into two stages. In the Instruction Stage,
the subject must stand with feet together, keep arms at side and listen to
instructions. In the Balance and Counting Stage, the subject must
raise the leg of his choice approximately 6 inches off the ground, toes
pointed out, keeping legs straight. While looking at the elevated
foot, count out load in the following manner: "one thousand and one", "one
thousand and two", etc, until told to stop. The officer will instruct
the subject to stop after 30 seconds. The subject is observed for the
following clues:
-
sways while balancing
-
uses arms to balance
-
hops
-
puts foot down
A person who exhibits 2 or more clues, as determined by the officer, will
fail the test and be classified as having an alcohol
concentration of .10 or above.
Sober People Fail Police Balance Tests Too
It should be noted that even HNTSA recognizes that factors such as age,
weight and medical problems will affect a person's ability to perform these
tests. It is therefore imperative that your lawyer discuss your
medical history with you.
Anthony Segura: NHTSA Trained & Qualified
Fort Bend DWI Lawyer Anthony R. Segura has successfully completed the
NHTSA SFST Training course and is qualified as an SFST Practitioner.
This is the same course attended by police officers.
