October 29, 2015

DWI Detection and Standardized Field Sobriety Testing Arrested Subject Did Not Arrest Subject Above Illegal Per Se Limit

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Arrested Subject Did Not Arrest Subject
Above
Illegal
Per Se
Limit
I
Officer decided to arrest the
subject and their BAC
was above the illegal per
se limit
II
Officer decided not to arrest the
subject and their BAC was
above the illegal per se limit
Below
Illegal
Per Se
Limit
III
Officer decided to arrest the
subject but their BAC
was below the illegal per
se limit
IV
Officer decided not to arrest the
subject and their BAC was
below the illegal per se limit
Correct Decision
8-13
Figure 1: Matrix of possible arrest decisions illustrates the four different decisions which
are present in all the validation studies. There are four quadrants, each representing a
different decision. The quadrants (I & IV), shaded in gray, represent a correct arrest
decision.
The remaining subjects, incorrect arrest decisions, fall into two other categories.
Members of the first group were not arrested, but tested above the illegal per se limit for
BAC (quadrant II). The Colorado Study noted that a number (approximately 33%) of
these individuals were considered alcohol tolerant and performed well on the SFSTs
even though their BACs were above the illegal per se limit. Although these release
decisions were recorded as errors based on the procedures outlined in the study, this
non arrest decision ultimately benefited the driver.
The subjects in quadrant III were arrested, but their BAC was below the illegal per se
limit. Many states stipulate in their statute that a driver is considered DWI if they are
either above the illegal per se limit for BAC or have lost the normal use of their mental
or physical faculties. Even though the arrests in quadrant III are legally justifiable
according to an individual state’s statute, these decisions are recorded as errors in the
research based on the procedures outlined in the study.
Each of these studies have shown that the SFST three test battery is a scientifically
validated and reliable method for distinguishing between impaired and unimpaired
drivers.
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HS 178 R5/13 9 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
First full field validation study using SFST
experienced law enforcement personnel
86% correct arrest/release decision based
on three test battery (HGN, WAT, OLS)
93% of those arrested had a BAC of 0.05
or higher
Colorado Field Validation
Study of SFST
8-14
“A Colorado Validation Study of Standardized Field Sobriety Test Battery”
• The Colorado SFST validation study was the first full field study that utilized law
enforcement personnel experienced in the use of SFSTs.
• The initial 1977 study utilized only a few experienced officers in DWI enforcement in
both a laboratory setting and field setting. These officers received approximately four
hours of training in field sobriety testing prior to the laboratory study.
• In the Colorado study, correct arrest/release decisions at a 0.05 BAC were 86%
accurate based on the three test battery (HGN, WAT, OLS). 93% of arrested drivers
had a BAC of 0.05 or higher. These results, by officers who were trained in the
Standardized Field Sobriety Testing curriculum, were substantially higher than the
initial 1977 study results.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
95% correct arrest decision based on
three test battery (HGN, WAT, OLS)
Validated SFSTs at 0.08 BAC and above
Florida Field Validation
Study of SFST
8-15
“Florida Validation Study of the Standardized field Sobriety Test Battery”
• The Florida SFST field validation study was undertaken in order to answer the
question of whether SFSTs are valid and reliable indices of the presence of alcohol
when used under present day traffic and law enforcement conditions.
• Correct decisions to arrest were made 95% of the time based on the three test battery
(HGN, WAT, OLS).
This was the second SFST field validation study that was undertaken.
This study was the first study conducted at the lower BAC limit of 0.08.
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HS 178 R5/13 10 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
91% correct arrest decision for 0.08 BAC
and above using three test battery (HGN,
WAT, OLS)
HGN is still most reliable of three-test
battery and supports arrest decisions at
0.08 BAC
San Diego Field Validation
Study of SFST
8-16
“Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 %”
• The San Diego SFST validation field study was undertaken because of the nationwide
trend towards lowering the BAC limits to 0.08. The question to be answered was “Do
SFSTs discriminate at BACs below 0.10%?”
• The study examined the validity of SFST’s for both .08% and .04%.
• Correct arrest decisions were made 91% of the time based on the three-test battery
(HGN, WAT, OLS) at the 0.08 level and above.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Based on this study:
HGN was 88% accurate
WAT was 79% accurate
OLS was 83% accurate
San Diego Field Validation
Study of SFST (Cont.)
8-17
• HGN was 88% accurate
• WAT was 79% accurate
• OLS was 83% accurate
The results of this study provide clear evidence of the validity of the three test battery to
support arrest decisions at above or below 0.08. It strongly suggests that the SFSTs
also identify BACs at 0.04 and above.
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HS 178 R5/13 11 of 62 Source: DWI Detection and
Standardized Field
Sobriety Testing
March 2013 Edition

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