![handle is hein.journals/lawprisk20 and id is 1 raw text is: Law, Probability and Risk (2021) 20, 1-13 doi:10.1093/lpr/mgab004
Advance Access publication on November 29, 2021
The high reported accuracy of the standardized field sobriety test is a
property of the statistic not of the test
GREG KANEt
10785 E Crestline Pl, Englewood, CO 80111
AND
ELIZABETH KANE
[Received on 2 February 2021; accepted on 9 August 2021]
OBJECTIVE In the 1990s as the legal blood alcohol limit for driving changed, validation studies
reported the Standardized Field Sobriety Test (SFST) to be accurate at discriminating between
Blood Alcohol Concentrations (BAC) above or below several legal limits: 0.10, 0.08, 0.05 and
0.04%. We investigated the contribution of the validation studies' choice of accuracy statistic to
the SFST's reported accuracy. METHODS Using the data set from a commonly cited SFST valid-
ation study, we calculated the arrest accuracy and overall accuracy of the SFST at identifying
BACs above or below 31 different target BACs from 0.00 to 0.30%. RESULTS At target BAC
0.30% the arrest accuracy of the SFST is 1%; at BAC 0.15%, 34%; at BAC 0.00%, 100%. The sta-
tistics arrest accuracy and overall accuracy describe the SFST, a test designed to identify changes
caused by alcohol, as less accurate when the changes are severe, more accurate when changes are
mild, and as 100% (arrest) and 93% (overall) accurate when there are no changes at all.
CONCLUSION The statistics overall accuracy and arrest accuracy to not quantify the probability
that impaired driving defendants who failed the SFST had an elevated BAC or were impaired.
Keywords: accuracy; prevalence; diagnostic testing; impaired driving; sobriety testing; statistics
1. Introduction
This paper is about statistical methods widely understood to validate the law enforcement
Standardized Field Sobriety Test (SFST); it is not about the sobriety test itself. The SFST is a phys-
ical examination, most often done at the roadside by a trained law enforcement officer in the course
of an impaired driving investigation. Developed beginning in the 1970s [1-3], and field tested in
projects sponsored by the National Highway Traffic Safety Administration (NHTSA) in the 1990s
[4-6], the procedure has been well described [7-13], and its statistical properties considered [14].
Initially investigated for its ability to identify elevated Blood Alcohol Concentration, the SFST is
also used [15] and investigated [16-23] as a method to identify impairment and the presence of vari-
ous drugs.
tEmail: GregKaneMD@gmail.com
© The Author(s) [2021]. Published by Oxford University Press. All rights reserved](ViewImageLocal?handle=hein.journals/lawprisk20&div=1&collection=&method=preview&ext=.png&size=3)
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