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.

Notes:_______________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

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.

Notes:_______________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

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.

Notes:_______________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

HS 178 R5/13 11 of 62 Source: DWI Detection and

Standardized Field

Sobriety Testing

March 2013 Edition