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How Cops Learn to Catch Drunks


Austin police cadets scientifically boozing their
volunteers. Sobriety test photo via Shutterstock.
This photo courtesy the author.

By Jeff Winkler


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(page 2)

Apart from the instructors looking over cadets’ shoulders, there are other reasons for nervousness. For one, says Sgt. Pruett, cadets have two chances to pass the live-scenario test. And failing it means failing out of the academy entirely.

The SFST themselves also are somewhat arbitrary—although cops nationwide strongly deny that. The SFST are, after all, the No. 1 way police successfully get dangerous drunks off the road. “The basis for all this is ... science, and there’s studies out there that are done on percentages,” says Sgt. Pruett. “So [the cadets] go over the scientific cases.”

Discuss DWIs with police officers long enough, and inevitably one “percentage” will come up: the supposed 91% accuracy of the SFST themselves. That figure comes primarily from an NHTSA test that is more than 30 years old.

“You don’t want to falsely arrest someone," says Cadet Arika Austin. "But we have a job to protect the public, and [to ensure] that people who are impaired don’t continue driving.”

In the original 1975 study, about 200 unemployed men were used as guinea pigs. The men were scientifically boozed (to an antiquated .10 BAC) in front of 10 police officers, who tested six different sobriety tests on them. The top-performing tests, i.e. the ones that seemed most indicative of inebriation, were the ones we have today. At the time, scientists claimed the tests had an 81% chance of correctly identifying intoxication.

With the publication of a seminal report in 1981, the three tests became the benchmark. As noted in an entertaining 2005 Washington Post story, police officers nationwide now had a scientifically sound sobriety test. No more would they have to resort to past tricks of the trade: “Some threw coins on the ground and ordered that only nickels or quarters be picked up. They would have a driver lean back and touch one finger to his nose. Count backward from 100 by threes. Trace a paper maze. Rapidly tap a telegraph key. [Or give] tongue twisters such as ‘Methodist, Episcopal, sophisticated statistics.’”

It wasn’t until states were forced to lower the DWI threshold to .08 BAC, in 1998, that the study was addressed again. Perhaps unsurprisingly, the chances of guessing “intoxication” increased to 91% where .08 BAC was the dividing line, and 94% at .04 BAC. (The NHTSA attributes this to officers’ increased “operational experience” with the field tests, rather than a lower BAC threshold.)

As scientifically appealing as the test was, it still had its skeptics. Most famous is a 1994 study during which 21 people were videotaped taking six field sobriety tests. Fourteen officers were then shown the tape and instructed to find-the-drunkard. Collectively, the cops said 46% of the subjects were under the influence. They were off by 46%. Every subject was stone-cold sober.

More recently, a 2005 study found that when a suspect isn’t, you know, obviously drunk, the probability of accurately guessing whether he or she is above or below .08 BAC using the SFST range from 30% to 60%. Even for the twitching eyes of HGN, said to be the most accurate test because it measures a person’s unconscious physiological reaction, there are “literally hundreds of known causes of nystagmus, most of which have nothing to do with intoxication.”

None of the above is to suggest that police are wrong in using the SFST as part of their toolkit—only that it must be hell on the cadets. Imagine being graded on a Rorschach test. “It’s almost an art as much as a science,” says Cadet Austin—albeit art with much higher stakes.

“It can go either way, and you don’t want to falsely arrest someone,” Austin adds, noting that she still finds borderline suspects to be particularly tricky to evaluate. “But also, we have a job to protect the public, and [to ensure] that people who are impaired don’t continue driving if they have been drinking.”

After the academy class spends about 45 minutes out in the parking lot, putting all their knowledge and nerves to the test, time is up. Pencils and flashlights down!

Ten minutes later, the cadets convene in a classroom for the big reveal. Who had been drunk and who had been sober?

Sitting attentively, the class watches as each volunteer is brought in. Sgt. Pruett asks the appropriate cadets if they would have arrested the individual for a DWI. Each time, there is at least some disagreement or hesitation among the cadets.

When Sgt. Pruett details the volunteer’s BAC during the various incremental periods (including just before being presented to the class), the officer-in-training who had done the testing either drops his or her head in failure, makes that embarrassed “oh no” face—or smiles slightly with relief. The students who had tested me hem and haw when asked if they would have made an arrest. (As it turned out, I was just slightly over the legal limit, at .083 BAC.)

“I think some people took it kind of hard,” chuckles Cadet Austin, after the fact. “You know, nobody wants to make a mistake. But I think we look at it for the most part as a learning experience.”

Jeff Winkler has written for VICE magazine, The Awl and The New Republic, among other publications, and can be reached by email at He also wrote about evangelical rehabs, "No Refusal" DWI nights, and a real-life breathalyzer tech for The Fix.

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