Field Sobriety Tests Face Legal and Scientific Challenges in New Jersey DWI Cases

Police and prosecutors in New Jersey must prove that a person charged with driving while intoxicated (DWI) was impaired by alcohol or drugs when they were operating a vehicle. They frequently do this with evidence that a person’s blood alcohol concentration (BAC) was 0.08 percent or higher, but they can also prove impairment in other ways. An officer’s observations of a driver’s behavior and appearance, when combined with evidence of the officer’s experience in assessing intoxication, can serve as evidence for the purpose of a DWI prosecution. Field sobriety tests (FSTs) allow officers to evaluate whether a person shows physical signs of intoxication and then offer testimony about how the person performed. The reliability of FSTs has some scientific support, but they remain controversial and subject to challenge by DWI defendants.

New Jersey’s implied consent law requires drivers to submit breath samples during DWI investigations, but this usually happens after an arrest. An officer who has stopped a vehicle on suspicion of DWI might use FSTs to establish probable cause for an arrest. The earliest examples of FSTs probably date back to the beginning of the automobile era. No uniform standard for FSTs existed in the U.S. prior to the 1970s. Different police departments developed their own FST regimens, with little to no scientific study into their accuracy or reliability in assessing impairment.

In 1975, the National Highway Traffic Safety Administration (NHTSA) retained the Southern California Research Institute (SCRI) to research multiple FSTs in order to identify the ones with the highest accuracy. The SCRI conducted laboratory and field tests, resulting in three Standardized Field Sobriety Tests (SFSTs) that the NHTSA now promotes as a uniform standard for the whole country. They are the Walk-and-Turn test, the One-Leg-Stand test, and the Horizontal Gaze Nystagmus (HGN) test.

Since the NHTSA first announced the SFSTs in the early 1980s, other studies have generally confirmed their reliability when properly administered by law enforcement officers. One 2006 study, for example, found that officers correctly assessed a driver’s impairment based on FST performance in 91 percent of cases. A 1981 study had confirmed the reliability of FSTs for drivers with a BAC of 0.10 percent, which was the legal limit at the time, or lower. The 2006 study focused on drivers with BAC levels of 0.08 percent or lower.

The HGN test has a less impressive track record of reliability than the other SFSTs. It is also known as the Follow-the-Finger test, since it involves the driver following the officer’s finger, or an object like a pen, with their eyes as the officer moves it from side to side. The purpose is for the officer to look for involuntary eye movements, known as nystagmus, that can be an indicator of alcohol intoxication. Subsequent research into the HGN test has led to significant questions about its reliability. Numerous other factors, including age, medical conditions or medication, and external stimuli could also cause nystagmus.

A knowledgeable and experienced DWI attorney can protect your rights and advocate on your behalf if you are facing a charge of alleged DWI in New Jersey. At Levow DWI Law, P.C., we have dedicated our entire law practice to representing New Jersey DWI defendants. We can help you understand the legal process and guide you through the court system. To schedule a free and confidential consultation with a member of our team, contact us today online or at (877) 593-1717.

More Blog Posts:

Five Factors Courts May Consider in Determining Whether a Driver Was Impaired in a New Jersey DWI Case, New Jersey DWI Attorney Blog, September 17, 2015

New Jersey Appellate Court Reverses DWI Conviction, Finding Problems with Field Sobriety Tests, Other Evidence, New Jersey DWI Attorney Blog, May 3, 2015

Field Sobriety Tests in New Jersey DWI Stops, New Jersey DWI Attorney Blog, February 14, 2015