Texas SFST Program
The Texas Standardized Field
Sobriety Testing Program
• Grant-funded through the National Highway Traffic
Safety Administration and the Texas Department of
Transportation.
• Provide free training to Texas Peace Officers in DWI
Enforcement and the Standardized Field Sobriety Tests
(SFST).
• The “go-to” organization for the SFST curriculum in
Texas and a resource for questions about DWI
enforcement.
What do we teach?
• 24-hour SFST Practitioner course
• 50-hour SFST Train-the-Trainer Instructor course
• 8-hour SFST Refresher course
• 8-hour Fundamentals of DWI Investigation and
Enforcement
• Full-time staff of 5 as well as 52 adjunct instructors
from around the state.
1
When do you know someone is
drunk?
What does the law say?
• Penal Code 49.04 Driving While Intoxicated
(a) A person commits an offense if the person is intoxicated
while operating a motor vehicle in a public place.
• Definition of "Intoxicated" means:
• (A) not having the normal use of mental or physical
faculties by reason of the introduction of alcohol, a
controlled substance, a drug, a dangerous drug, a
combination of two or more of those substances, or any
other substance into the body; or
• (B) having an alcohol concentration of 0.08 or more
Three Phases of DWI Detection
• Vehicle in Motion
• Personal Contact
• Pre-Arrest Screening
Officers make a decision based on the “totality of the
circumstances”.
2
Vehicle in Motion
Starts with the initial observation of the vehicle in
operation
The decision as to whether to stop the vehicle
The observation of the stop
Stops need only be based on reasonable suspicion.
Effects of Impairment on Drivers
• Slowed reactions
Blood Alcohol Concentration
• Impaired judgment –
willingness to take risks
0.03
0.05
Slowed
Reactions
Impaired
Judgment
0.08
0.10
• Impaired vision
• Poor Coordination
Impaired
Poor
Vision Coordination
Recognition of the Initial Cues
What does the officer see:
• Moving violation?
• Equipment violation?
• Other violation?
• Unusual operation?
• Anything else?
3
Personal Contact
The interview and observation of the driver
The decision whether to have the driver exit the vehicle
The observation of the exit
What is the officer looking for?
• What do they see?
• What do they hear?
• What do they smell?
Some of the things officers observe
• Bloodshot eyes
• Soiled clothing
• Fumbling Fingers
• Alcohol Containers
• Drugs/Paraphernalia
• Bruises, bumps,
scratches
• Slurred speech
• Admission of drinking
• Inconsistent responses
• Unusual statements
• Abusive language
• Alcoholic beverage odor
• Marihuana
• Cover up odors
• Unusual odors
4
Interview of the suspect
• It is during the personal contact stage that the officer
gathers information from the suspect
• At this time multiple signs of intoxication may occur
• Slurring, mumbled speech
• Confusion, slow response to questions and directions
• Slow or careful movements
Pre-Arrest Screening
• Standardized Field Sobriety Tests
• Horizontal Gaze Nystagmus
• Walk and Turn
• One Leg Stand
Where did the tests come from?
• Ft. Lauderdale study 1975
• After face-to-face contacts and testing of drivers, officers only
correctly identified drivers who were 0.10 to 0.20 BAC 22% of
the time.
• NHTSA contacted with SCRI to develop more accurate
tests
• California 1977 Lab study
• California 1981 Lab and Field studies
• Maryland, Washington DC, Virginia, and North Carolina 1983
–Field study
5
Research results
Original Results 1981
0.10 BAC
San Diego Study 1998 –
0.08 BAC
• HGN by itself – 77%
• Walk & Turn by itself– 68%
• One Leg Stand by itself – 65%
• HGN by itself – 88%
• Walk & Turn by itself – 79%
• One Leg Stand by itself – 83%
4 clues on HGN, 2 clues on W&T, and 2 clues on OLS
What do they learn from the tests?
• Officers are looking for clues
• Horizontal Gaze Nystagmus – max of 6 clues; min 4 clues
• Walk and Turn – Max of 8 clues; min of 2
• One Leg Stand – Max of 4 clues; min of 2
The officer does not have to have the minimum number of
clues on each test to make a determination that the person is
intoxicated.
Totality of the circumstances.
So what are the clues?
HGN –
1st they check for Equal Pupil Size, Resting Nystagmus, & Equal
Tracking to determine if the driver is a candidate.
The officer looks for three clues in each eye, in this order:
1.
Lack of Smooth Pursuit
2.
Distinct and Sustained Nystagmus at Maximum Deviation
3.
Onset of Nystagmus Prior to 45 degrees.
The officer then checks for Vertical Gaze Nystagmus – this is not a
clue, rather an observation. It may be present in those under the
influence of high doses of alcohol for that individual or some other
drugs.
6
Horizontal Gaze Nystagmus
A clue may be present in one eye, but not in another eye.
A driver may still be over a 0.08 BAC, but have fewer than 4
clues.
There are three categories of drugs which cause HGN:
• Central Nervous System Depressants
• Dissociative Anesthetics
• Inhalants
Walk & Turn and One Leg Stand
Walk and Turn
The 8 clues are:
• Can’t balance during
instructions
• Starts too soon
• Uses arms for balance
• Misses heel to toe
• Steps off line
• Improper turn
• Incorrect number of steps
• Stops while walking
One Leg Stand
The four clues are:
• Puts foot down
• Uses arms for balance
• Sways while balancing
• Hops
*Specific Criteria is set for each clue in all three tests
What other tests do they use?
There are other valid tests that can be used, but no
others that have been validated.
• Finger Count
• Finger to Nose
• Paper Trace
• Counting
• Alphabet
7
When do officers use other tests?
To supplement the SFST or when the driver is not a
candidate for the tests, due to an injury, disease or other
physical condition.
Emerson vs. State (Texas Ct. of Crim. App 1994)
• Allows a properly trained officer to testify about the
Horizontal Gaze Nystagmus test.
• Requires that the officer must follow the HGN
technique as taught by NHTSA and the State of Texas.
QUESTIONS?
8
VALIDATION OF THE STANDARDIZED F IELD SOBRIETY TEST
B ATTERY AT BAC S B ELOW 0.10 P ERCENT
F INAL REPORT
Submitted to:
U.S. DEPARTMENT OF T RANSPORTATION
N ATIONAL HIGHWAY T RAFFIC S AFETY A DMINISTRATION
Jack Stuster
Marcelline Burns
August 1998
A NACAPA SCIENCES , INC .
P.O. Box 519
Santa Barbara, California 93102
-- ii--
Technical Report Documentation Page
1. Report No.
2. Government Accession No.
3. Recipient’s Catalog No.
DOT HS ?
4. Title and Subtitle
5. Report Date
August 1998
Validation of the Standardized Field Sobriety Test Battery at
BACs Below 0.10 Percent
7. Author(s)
Jack W. Stuster, PhD, CPE, and Marcelline Burns, PhD
9. Performing Organization Name and Address
6. Performing Organization Code: n/a
8. Performing Organization Report No. n/a
10. Work Unit No. (TRAIS)
Anacapa Sciences, Inc.
P.O. Box 519
Santa Barbara, CA 93102
11. Contract or Grant No.
DTNH22-95-C-05192
12. Sponsoring Agency Name and Address
13. Type of Report and Period Covered
National Highway Traffic Safety Administration
400 Seventh Street, SW
Washington, D.C. 20590
Final Report
15. Supplemental Notes
14. Sponsoring Agency Code
James F. Frank, PhD was the Contracting Officer’s Technical
Represenative (COTR) for this project.
16. Abstract
This study evaluated the accuracy of the Standardized Field Sobriety Test (SFST) Battery to assist officers in
making arrest decisions for DWI at blood alcohol concentrations (BACs) below 0.10 percent. NHTSA’s SFST battery
was validated at 0.10 percent BAC in 1981. The trend to reduce statutory DWI limits to 0.08 percent BAC prompted
this research project.
The research was composed of several project tasks, including planning, site-selection, training, data entry, and
data analysis, in addition to the actual conduct of a major field study. The City of San Diego, California, was selected
as the site. Seven officers of the San Diego Police Department’s alcohol enforcement unit were trained in the
administration and modified scoring of NHTSA’s SFST battery (i.e., Horizontal Gaze Nystagmus-HGN, Walk and Turn,
and One Leg Stand). SFST scoring was adjusted: the observation of four HGN clues indicated a BAC ≥0.08 percent
(rather than four clues indicating a BAC ≥0.10 percent), and the observation of two HGN clues indicated a BAC
≥0.04 percent. During routine patrols, the participating officers followed study procedures in administering SFSTs
and completing a data collection form for each test administered. The officers’ final step in each case was the
administration of an evidentiary breath alcohol test.
Data analysis found the SFSTs to be extremely accurate in discriminating between BACs above and below 0.08
percent. The mean estimated and measured BACs of the 297 motorists tested were 0.117 and 0.122, respectively;
the difference between the means (0.005 percent BAC) is very small and operationally irrelevant. Further, analyses
found the HGN test to be the most predictive of the three components of the SFST battery (r=0.65), however a
higher correlation was obtained when the results of all three tests were combined (r=0.69).
Decision analyses found that officers’ estimates of whether a motorist’s BAC was above or below 0.08 or 0.04
percent were extremely accurate. Estimates at the 0.08 level were accurate in 91 percent of the cases, or as high as
94 percent if explanations for some of the false positives are accepted. Officers’ estimates of whether a motorist’s
BAC was above 0.04 percent but lower than 0.08 percent were accurate in 94 percent of the decisions to arrest and
in 80 percent of cases overall. Also, the officers and prosecutors who were interviewed about the SFSTs found the
test battery to be acceptable for field use to establish probable cause for DWI arrest.
The results of this study provide clear evidence of the validity of the Standardized Field Sobriety Test Battery to
discriminate at 0.08 percent BAC, using a slightly modified scoring procedure. Further, study results strongly
suggest that the SFSTs also accurately discriminate at 0.04 percent BAC.
17. Key Words
18. Distribution Statement
DWI, DUI, detection, field sobriety, performance tests,
alcohol, law enforcement, highway safety
19. Security Classif. (of this report)
20. Security Classif. (of this page)
Unclassified
Unclassified
--iii--
21. No. of Pages
22. Price
-- iv --
Final Report
Validation of the SFST Battery at BACs Below 0.10 Percent
E XECUTIVE SUMMARY
This report documents the research activities and presents the results of a
study conducted for the National Highway Traffic Safety Administration (NHTSA)
to evaluate the accuracy of the Standardized Field Sobriety Test (SFST) Battery to
assist officers in making arrest decisions and to discriminate blood alcohol
concentrations (BACs) below 0.10 percent. NHTSA’s SFST battery was validated at
0.10 percent BAC in 1981. The trend to reduce statutory DWI limits to 0.08 percent
BAC prompted this research project.
DESCRIPTION OF THE RESEARCH
The research was composed of several project tasks, including planning, siteselection, training, data entry, and data analysis, in addition to the actual conduct of
a major field study. The City of San Diego, California, was selected as the site of the
field study. Seven officers of the San Diego Police Department’s alcohol enforcement
unit were trained in the administration and modified scoring of NHTSA’s SFST
battery (i.e., Horizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand). SFST
scoring was changed slightly: the observation of four horizontal gaze nystagmus
(HGN) clues indicated a BAC ≥0.08 percent (rather than four clues indicating a BAC
≥0.10 percent), and the observation of two HGN clues indicated a BAC ≥0.04 percent.
During routine patrols, the participating officers followed study procedures in
administering SFSTs and completing a data collection form for each test
administered during the study period. The officers’ final step in each case was the
administration of an evidentiary breath alcohol test.
RESULTS
The participating officers completed a total of 298 data collection forms; only
one case was eliminated from analysis because the motorist refused all forms of
BAC testing. Data analysis found the SFSTs to be extremely accurate in
discriminating between BACs above and below 0.08 percent. The mean estimated
and measured BACs of the 297 motorists tested were 0.117 and 0.122, respectively;
the difference between the means (0.005 percent BAC) is very small and
operationally irrelevant. Further, analyses found the HGN test to be the most
predictive of the three components of the SFST battery (r=0.65), however a higher
correlation was obtained when the results of all three tests were combined (r=0.69).
The results of decision analyses provide clear indication of SFST accuracy.
Decision analyses found that officers’ estimates of whether a motorist’s BAC was
above or below 0.08 or 0.04 percent were extremely accurate. Estimates at the 0.08
level were accurate in 91 percent of the cases, or as high as 94 percent if explanations
for some of the false positives are accepted. Officers’ estimates of whether a
motorist’s BAC was above 0.04 but under 0.08 were accurate in 94 percent of the
decisions to arrest and in 80 percent of the relevant cases, overall.
-- v --
Final Report
Validation of the SFST Battery at BACs Below 0.10 Percent
Finally, the officers and prosecutors who were interviewed about the SFSTs
found the test battery to be fully acceptable for field use to establish probable cause
for DWI arrest.
IMPLICATIONS
The results of this study provide clear evidence of the validity of the
Standardized Field Sobriety Test Battery to discriminate above or below 0.08 percent
BAC, using a slightly modified scoring procedure. Further, study results strongly
suggest that the SFSTs also accurately discriminate above or below 0.04 percent BAC.
-- vi --