Category Archives: Field Sobriety Tests

Field Sobriety Tests Found to be Inaccurate

Proponents of the so-called “standardized” field sobriety tests (SFSTs) have long pointed to federally-funded field studies which indicate a high correlation between performance on the tests and actual blood alcohol concentrations (BAC). 

Subsequent studies, however, have called those conclusions into question.

Originally, the National Highway Traffic Safety Administration (NHTSA) paid a private group, the Southern California Research Institute, to conduct studies to find which among the various field sobriety tests used by police were most effective and to develop a standardized 3-test battery.  SCRI subsequently reported to NHTSA that a battery of walk-and-turn, one-leg-stand and nystagmus provided a strong correlation with breath test results.

Confronted with questions about those conclusions, NHTSA later commissioned the same researcher who had conducted the original studies, Marcelline Burns, to  corroborate the accuracy of her own tests of the SFSTs – rather than commission an independent source. 

Burns accompanied a small number of San Diego officers conducting actual DUI investigations in the field.  After administering the SFSTs, the officers were asked to guess whether suspects had blood alcohol  concentrations (BAC) over or under .08%.   Burns reported a 91% correlation between SFSTs and BAC over-under estimates, thereby validating the battery of tests she had helped create.

A subsequent scientific article challenged Burns’ corroboration of her own research.  In Hlastala, Polissar and Oberman, “Statistical Evaluation of Standardized Field Sobriety Tests”, 50(3) Journal of Forensic Sciences 1 (May 2005), the raw data used in the validation study were obtained from NHTSA through the Freedom of Information Act.  The methodology used was then reviewed and the data subjected to statistical analysis.

The methodology was found to be seriously flawed in a number of respects.  For one thing, many of the suspects had very high BACs, making estimates of whether a suspect was over .08% obvious regardless of SFST performance.  For another, there was no attempt to isolate the influence of SFST performance from other factors:  officers estimated BACs after the field sobriety tests, but they also took into account earlier observations, such as erratic driving, slurred speech, odor of alcohol, flushed face, admissions as to amount of alcohol consumed, etc.

The most glaring defect in Burns’ corroborative study was that “all police officers  participating in the study were equipped with NHTSA-approved portable breath testing devices”.  In other words, the San Diego officers already had the results of portable breath tests before they were asked to estimate the BACs later obtained at the station!

After reviewing the flawed methodology, the raw data was then statistically analyzed.  The conclusions:

If we consider three ranges of MBAC [measured blood alcohol content], 0.00% to 0.04%, 0.04% to 0.08%, and 0.08% to 0.12%, the officers’ EBAC [estimated blood alcohol content] overestimated the MBAC 76%, 67% and 48% of the time, and underestimated it 14%, 26% and 28% of the time. 

In other words, officers relying upon field sobriety tests were far more likely to overestimate  BACs than underestimate — particularly with those suspects having very low BACs. 

(T)he utility of the SFST depends very much on how intoxicated an individual is.  Accuracy (and specificity) are low when individuals are close to 0.08% MBAC, but if the individuals are quite intoxicated, such as above 0.12%, then accuracy is high.

In borderline cases involving persons at or under the legal limit, then, officers were very poor at estimating blood-alcohol levels based upon SFSTs.  And it is these cases, of course, that are critical.  Suspects with high BACs are relatively easy to single out without the help of field tests; it is for the closer cases, particularly those who are innocent (below .08%), that the SFSTs are designed.  And it is with these very cases that the tests apparently fail. 

Put another way, accuracy in using field sobriety tests is high when they are not needed — and low when they are.

For another independent study conducted by Professor Spurgeon Cole of Clemson University, in which he found field sobriety tests to be worthless, see Are Field Sobriety Tests Designed for Failure?.

Field Sobriety Tests “Unreliable” for Older Drivers

In just another example of law enforcement's one-size-fits-all approach to drunk driving cases, Dr. Lance L. Gooberman, M.D., offers the following comments:

The National Highway Traffic Safety Administration, based upon studies done in 1977 and 1983, determined that standardized field sobriety tests were unreliable in those over age 60. This is reflected in the National Highway Traffic Safety Administration manual from 1991. In 2006 it was changed to age 65, however, this was not based upon any additional data.

A recent British study indicates that the breakpoint for reliability on field sobriety tests is the age of 40.   Dixon, Clark and Tiplady, Evaluation of a Road Side Impairment Test Device Using Alcohol, 41 Accident Analysis and Prevention, 412-418 (2009). This is more consistent from a medical perspective. Therefore, field sobriety tests cannot be relied upon in people greater than 40 years of age.

For further examples of the "one-size-fits-all" road to conviction, particularly with blood and breath alcohol analysis, see my earlier post Guilty…of Not Being Average?  

Field Sobriety Tests Are Designed to be Failed

Roadside field sobriety tests (“FSTs”) are commonly used by police officers in DUI investigations to determine whether a driver is under the influence of alcohol. Typically, they consist of a battery of 3-5 excercises, such as heel-to-toe, one-leg stand, “nystagmus” (“follow the pencil with your eyes”), finger-to-nose, alphabet recitation, “Rohmberg” (eyes-closed, modified position-of-attention), etc. The officer will subjectively decide whether the individual “failed”.

These DUI tests have an aura of scientific credibility to juries. Unfortunately, however, they have no real basis in science and are almost useless in a drunk driving case.

First, as any traffic officer or DUI attorney knows, the decision to arrest is made at the driver’s window; the FSTs given supposedly to determine probable cause to arrest are actually for the purpose of providing “evidence” to support the officer’s opinion of intoxication.

Second, since the officer has already made up his mind, his subjective decision as to whether a person passed or failed field sobriety tests is suspect: as with any human, he will “see” what he expects to see.

Third, the conditions under which the field sboriety tests are taken almost guarantee failure: usually late at night, possibly cold, along a graveled or sloped roadside, with bright headlights from passing cars (setting up wind waves), the officer’s flashlight and patrol car’s strobe and headlights providing the lighting — and given to a person who is nervous, frightened and completely unfamiliar with the tests.

Fourth, field sobriety tests are irrelevant and, in fact, designed for failure. What scientific basis exists to validate FSTs in a DUI investigation? Only a “study” by a private business firm, the “Southern California Research Institute”, with a grant from the federal government to find a “standardized” battery of usable DUI tests.

To earn their money, SCRI came up with three tests which, they said, were not foolproof but were much better than all of the other FSTs that were being used. These three tests were heel-to-toe, one-leg-stand and nystagmus.  Yet after some study even this company concluded that, using the three standardized tests, 47 percent of the subjects tested would have been arrested for DUI — even though they were under the then-.10% limit.  Burns and Moskowitz, Psychophysical Tests for DWI Arrest: Final Report, DOT-HS-802-424, NHTSA, 1977.

Unhappy with this, the federal government sent the company back to the drawing board and, in 1981 the firm came up with some better figures: only 32 percent of those who “failed” the tests were actually innocent. (Tharp, Burns and Moskowitz, Development and Field Sobriety Test of Psychophysical Tests for DWI Arrests: Final Report, DOT-HS-805-864, NHTSA, 1981.) Thus, SCRI was paid to put their stamp of approval on a set of field sobriety tests.

But what has been the reaction of the (non-profit) scientific community? In 1991, Dr. Spurgeon Cole of Clemson University conducted a study on the accuracy of FSTs. His staff videotaped individuals performing six common field sobriety tests, then showed the tapes to 14 police officers and asked them to decide whether the suspects had “had too much to drink and drive”. Unknown to the officers, the blood-alcohol concentration of each of the 21 DUI subjects was .00% — stone sober.

The results: the officers gave their opinion that 46% of these innocent people were too drunk to drive! In other words, the field sobriety tests were hardly more accurate at detecting intoxication than flipping a coin. Cole and Nowaczyk, “Field Sobriety Tests: Are they Designed for Failure?”, 79 Perceptual and Motor Skills Journal 99 (1994).

Driver Arrested for DUI After Passing All 6 Field Sobriety Tests

The purpose of "field sobriety tests" (FSTs) is, of course, to determine if a driver is under the influence of alcohol. Rather than let the officer arrest anyone he wants, the tests supposedly provide objective evidence of impairment from alcohol.     

The usual DUI investigation includes the administration of 3 FSTs to the driver.  Commonly, this consists of the 3 "standardized" FSTs (SFSTs) recommended by the National Highway Traffic Safety Administration: walk-and-turn, one-leg-stand, and horizontal gaze nystagmus (the "eye test").  If some cops aren’t happy with the results, they may administer one or two more tests, hoping that the suspect will finally fail one of them.  

And then again, some cops just ignore the evidence…

Tennessee: Improper to Arrest Someone for Passing DUI Test

Knoxville, TN.  Sept. 5 — A Tennessee motorist who passed six roadside sobriety tests should not have been arrested for driving under the influence of alcohol (DUI), the state Court of Criminal Appeals ruled Friday. The three-judge panel rejected the attempt by prosecutors to overturn a trial court’s finding that David D. Bell should not have been taken into custody on January 12, 2010 after he displayed "excellent" mental acuity after being pulled over by a county sheriff’s deputy.

Bell had made a wrong turn in a construction area, briefly driving on the wrong side of the road — a mistake that a number of other confused drivers had made that day. Sevierville Police Officer Timothy Russell, who had extensive DUI training, arrived on the scene to take over from the deputy. Russell asked Bell to perform a four-finger count; say the alphabet from the letter G to S; identify the year of his fifth, sixth or seventh birthday; perform a one-legged stand while counting to thirty; and do a nine-step walk-and-turn. On the stand, Officer Russell testified that his mental performance was excellent, but that Bell "did not plant and turn as I had instructed him to." So Russell placed Bell under arrest.

Officer Russell admitted he did not follow proper procedure by turning off his flashing blue lights, which is a known source of distraction for the plant-and-turn test. After reviewing dashcam video from that night, the trial judge rejected Officer Russell’s conclusion.

"I honestly think that he did pretty dog-gone good on the field sobriety tests, better than most I’ve seen," Sevier County Circuit Court Judge Rex Henry Ogle observed. "I couldn’t pass them as well as he did."

Judge Ogle found the initial traffic stop legitimate but granted a suppression motion because the arrest went too far. The three-judge appellate panel also reviewed the videotape and sided with the trial judge. The appeals court found ample reason to suspect Bell might have been intoxicated, but the probable cause evaporated after testing.

"We interpret the slightly more colorful comments made by the trial court in its ruling from the bench on the defendant’s suppression motion as a finding, as a factual matter, that the defendant passed all of the field sobriety tests that he was given," Judge John Everett Williams wrote for the three-judge panel. "The state is not required to perform field sobriety tests on an individual prior to arresting him or her for driving under the influence. However, if the state chooses to administer such tests, it may not simply disregard the results if the individual involved performs them successfully. Had the defendant failed any of the field sobriety tests, we have no doubt that the state would have argued that the defendant’s failure provided strong evidence in support of probable cause. We believe that the defendant’s consistent success on a battery of such tests is likewise compelling evidence — in the other direction."

To paraphrase the great Humphrey Bogart film, Treasure of the Sierra Madre…"FSTs? FSTs!  I don’t need no stinkin’ FSTs!"

A “Fraudulent” Field Sobriety Test?

The critical part of any drunk driving investigation is the administration of "field sobriety tests" (FSTs).  These usually consist of a battery of excercises involving balance, coordination and mental agility — and are difficult to perform for even a sober person under ideal conditions (see "Field Sobriety Tests: Designed for Failure?").  Although there are many different tests (finger-to-nose, alphabet, etc.), an increasing number of law enforcement agencies are requiring their officers to use only the federally-recommended battery of three "standardized" FSTs.  The most recently developed of these three is horizontal gaze nystagmus (HGN), commonly known as the "eye test".  It is particularly effective in trial not because of its accuracy, but rather because it appears to jurors as scientific in nature.

As I have indicated in previous posts, however, HGN as a test for intoxication is fundamentally flawed and rarely understood or properly administered by police officers.  See "Nystagmus: The Eye Test", "Nystagmus: The Eye Test (Part 2)", and "Nystagmus: The Eye Test (Part 3)".

A scientific study (144(3) Science and Justice 133-139) has investigated the scientific validity of the nystagmus test:

The Horizontal Gaze Nystagmus (HGN) test was conceived,
developed and promulgated as a simple procedure for the determination of the blood alcohol concentration of drivers suspected of driving while intoxicated (DWI). Bypassing the usual scientific review process and touted through the good offices of the federal agency responsible for traffic safety, it was rushed into use as a law enforcement procedure, and was soon adopted and protected from scientific criticism by courts throughout the United States. In fact, research findings, training manuals and other relevant documents were often held as secrets by the state. Still, the protective certification of its practitioners and the immunity afforded by judicial notice failed to silence all the critics of this deeply flawed procedure….

In 1998 the integrity of the statistical evaluation of the original research upon which the validity of the tests rested was unfavorably reviewed [5]. In 2001 new research indicated that the Horizontal Gaze Nystagmus (HGN), the cornerstone of the test battery was fundamentally flawed and that the HGN test was improperly conducted by more than 95% of the police officers who used it to examine drivers suspected of driving while intoxicated (DWI) [6]. This summary critique demonstrates that it is scientifically meretricious and that the United States Department of Transportation indulged in deliberate fraud in order to mislead the law enforcement and legal communities into believing the test was scientifically meritorious and overvaluing its worth in the context of criminal evidence….

 Deliberate fraud.  Pretty strong language for a scientific journal.  After reviewing the flawed and deceptive justifications for using nystagmus in DUI investigations, the researchers concluded that the test was essentially without scientific validity.

The state’s argument for the field sobriety tests does not rest on
proof of merit, but upon
qui tacet consentit reasoning that those tests have been so widely accepted they must have been subjected to some kind of review prior to adoption in the many jurisdictions where they are used, that somewhere along the way someone would have spotted the flaws and shortcomings. Considering that the student manual was originally considered to be a confidential state document and was only obtained through an Open Records Act request, silence from the scientific community cannot be considered an endorsement of the program.