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Traffic Law

Combined Measures Accuracy of Standardized Field Sobreity Test (SFST)

When the component tests of the SFST battery are combined, officers are believed to be accurate in 91 percent of DWI cases, overall, and in 94 percent of DWI cases if explanations for some of the false positives are accepted (Stuster and Burns, 1998).

The original NHTSA research found different accuracies for the SFST Battery than reported in the more recent study. Tharp, Burns, and Moskowitz (1981) reported accuracies of 77 percent for the HGN, 68 percent for the Walk and Turn, and 65 percent for the One Leg Stand components; 81 percent of officers’ arrest decisions at 0.10 BAC were correct when all three measures were combined.

In contrast, Stuster and Burns (1998) found greater accuracies in making arrest decisions on the basis of SFST results in their study at 0.08 percent BAC, as described previously and summarized in the following table.

*Comparison of SFST Accuracies 1981 vs. 1998*

Study: Combined Tharp, Burns, & Moskowitz (1981)

bq. BAC: 0.10
HGN: 77%
WAT: 8%
OLS: 65%
*Combined: 81%*

Study: Stuster & Burns (1998)

bq. BAC: 0.08
HGN: 88%
WAT: 79%
OLS: 83%
*Combined: 91%*

The greater component and overall accuracies found during the 1998 study are attributable to 17 years of law enforcement experience with the SFSTs since the original study and a lower criterion BAC than in the original study (i.e., 0.08 vs. 0.10 percent).