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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?.
 

DUI BLOG

A local news station in Lee County, Florida recently ran an investigative series into Florida drunk driving accidents and DUI incidents. Reporters found that in many cases drivers caught on DUI charges are getting their licenses back and are being allowed to drive again quickly after being ticketed for DUI.

Under Florida law, drivers who have been accused of DUI are allowed to have an administrative hearing with the Florida Department of Highway Safety and Motor Vehicles. This hearing occurs before the DUI trial and allows the defendants to argue for their license. While Florida law allows officers to immediately take away the license of someone who is accused of DUI, these hearings, according to investigative reporters, gave back licenses to hundreds of people in Southern Florida in just a three month period.

Someone who is accused of driving under the influence has ten days to request an administrative hearing. At the hearing, officers decide whether to invalidate the license suspension and return the driver’s license. According to investigative reports, in 2009 more than 5200 drivers in Florida received their licenses back due to these hearings. In some cases, drivers had been impaired and had been unable to pass a breathalyzer test but had their licenses reinstates because police officers failed to follow testing standards or guidelines when administering the tests.

In some cases, arresting officers did not appear at the administrative hearings, which also allowed the drivers to have their licenses reinstated. Florida is changing that particular law. After July 2010, a driver does not automatically have his or her license reinstated if the arresting officer does not show up at a DMV administrative hearing. As well, police authorities are cracking down on police officers who fail to show up for the hearings.

The investigative report does suggest the importance of good communication between the DMV and authorities. While DMV administrative hearings do not have a bearing on criminal DUI trials – that is, someone who has a license reinstated at a DMV hearing may still be found guilty at a criminal DUI trial – the case is troubling for motorists. This is because it does suggest that drivers who may cause Florida car accidents due to DUI may be back on the roads – legally – after drinking and driving. The DMV hearings are intended to give drivers a fair chance to get their licenses back but more studies need to be done to determine whether reinstatements are leading to more Florida car accidents.

Florida Car Accident Lawyer Blog