Graph of FST accuracy
This is a graph of the never-before-available-to-the-public data in the NHTSA's 1998 San Diego validation study. Each point represents one driver in the study: total FST score on the x-axis, BAC on the y-axis. If you know a driver's FST score, do you really know their BAC?

Notice that of the 296 drivers studied only three had BACs of zero. The FST performance of people with no alcohol on board is unknown.

Of 296 people tested only 4 passed the test at the 0.04% level. At that level, on innocent drivers, the FST gave the wrong answer 93% of the time.