Sobriety testing

SIGNIFICANCE: An important tool in combating drunk driving, sobriety testing can be crucial to establishing probable cause for making arrests and providing evidence to secure convictions of suspected drunk and drugged drivers.

Police officers administer sobriety tests to drivers they suspect of driving while impaired by alcohol or drug ingestion for two reasons. First, they need to establish probable-cause foundations for making arrests; second, the results of the tests are used to aid in prosecutions to establish that violations of law have occurred. Sobriety tests are of two basic kinds: field and chemical. Field sobriety tests (FSTs) are subjective in nature; that is their validity relies upon the observations of the arresting officers. Chemical sobriety tests are considered to be objective, as their results are obtained through laboratory analyses.

One objective measure of a driver’s sobriety is the level of the driver’s blood alcohol concentration (BAC). That level is calculated scientifically by measuring the amount of ethanol (ethyl alcohol, an odorless form of alcohol) in a person’s bloodstream from blood, breath, or urine samples. All fifty US states have legally defined presumptive limits of blood alcohol concentration. Under those definitions, drivers of motor vehicles are presumed to be under the influence of alcohol when their blood alcohol concentration exceeds the limits of the states in which they are driving. The limit is .08 percent in most states, and .10 percent in others.

Field Sobriety Tests

Field sobriety tests are designed to give officers in the field approximate ideas of the sobriety of suspected drunk-driving offenders. Such tests do not confirm either illegal intoxication or sobriety; they serve only as guidelines. Officers carrying breath-analyzer equipment in the field can administer objective tests immediately. Otherwise, they must ask suspects to submit to subjective tests.

Every law-enforcement agency in America has a policy for administration of subjective field sobriety tests, but the National Highway Traffic Safety Administration (NHTSA) has developed a standardized set of tests since the early 1970’s to assist officers in their arrest decisions.

The most commonly used standardized field test is called the horizontal gaze nystagmus (HGN) test. This test is designed to help officers observe whether any jerkiness (or bounce) appears in the eyes of suspected offenders when their eyes follow a stimulus from side to side. Eye jerkiness may indicate intoxication, but officers are trained to know that such eye movements may be present even without intoxication, as in the case of certain nerve disorders.

Officers also watch for other subjective symptoms of intoxication, such as bloodshot and watery eyes, slurred speech, and poor balance. Other field sobriety tests include balance and coordination trials, such as walking in a straight line, heel to toe; counting on fingers; and reciting the alphabet. When officers believe that suspects have been driving while intoxicated, the tests have served their purpose as pre-arrest indicators of intoxication and arrests are made. Suspects are then transported to facilities for the administration of chemical sobriety tests.

Chemical Sobriety Tests

In most states, suspects arrested for driving while under the influence of alcohol (DUI) may choose the types of chemical sobriety tests that are administered to them. Some states require offering two options; others require three. Failure to submit to a chemical test after arrest usually results in revocation of driving privileges.

Chemical sobriety tests include tests of samples of blood, breath, and urine. Blood and urine tests are usually administered when arresting officers suspect that the drivers have ingested drugs other than alcohol. Such tests are conducted in hospitals and jail facilities. Persons administering blood tests must be medically certified to draw blood. However, breath tests may be administered by anyone certified to operate a breath analyzer, and arresting officers frequently administer such tests. Urine samples may be taken by any person associated with the arrest. Both law enforcement and arrested drivers prefer breath tests, probably because their results are known immediately and do not require the time-consuming analyses of blood and urine tests.

Breath tests are conducted on the theory that alcohol escapes from the body through the breath. Most law-enforcement agencies use breath-analyzer machines produced under the trade names of Intoxilizer, Intoximeter, and Breathalizer because of the wide acceptance of their results by courts. When officers in the field carry a portable breath analyzer, the field sobriety tests they administer are considered to be objective.

Blood samples, which are usually drawn at community hospitals, are maintained under strict chain of custody standards until they are analyzed by laboratories. Afterward, they are either used in trials or are destroyed. Urine samples are usually collected at police stations, jail facilities, or hospitals. The samples are witnessed by officers who thereafter maintain the same chain of custody standards that are used with blood samples.

Regardless of the types of sample taken, officers are aware that blood alcohol concentrations in human bodies diminish at the rate of approximately .02 percent per hour. Consequently, the samples must be collected as soon as possible after arrests are made.

Bibliography

Dietrich, James J. Horizontal Gaze Nystagmus: The Science and the Law—A Resource Guide for Judges, Prosecutors, and Law Enforcement. Washington, D.C.: National Highway Traffic Safety Administration, 1999. Practical guide to administering horizontal gaze nystagmus tests to suspected drunk drivers.

"Field Sobriety Test." Cornell Law School, Aug. 2021, www.law.cornell.edu/wex/field‗sobriety‗test. Accessed 10 July 2024.

Homel, Ross. Policing and Punishing the Drunk Driver: A Study of General and Specific Deterrence. New York: Springer-Verlag, 1988. General study of methods of combating drunk driving through law enforcement.

Jacobs, J. B. Drunk Driving: An American Dilemma. Chicago: University of Chicago Press, 1992. Broad synthesis by a law professor on all aspects of drunk driving in the United States, from myths about the nature of the problem to the trend toward tougher enforcement of drunk driving laws.

Jasper, Margaret, et al. DWI, DUI and the Law. New York: Oceana, 2004. Lay guide to drunk driving laws in the United States. Covers criminal justice procedures, drunk driving statistics, and other related subjects.

Laurence, Michael D., John R. Snortum, and Franklin E. Zimring, eds. Social Control of the Drinking Driver. Chicago: University of Chicago Press, 1988. Sociological study of the causes and effects of drunk driving.

Robin, Gerald D. Waging the Battle Against Drunk Driving: Issues, Countermeasures and Effectiveness. Westport, Conn.: Greenwood Press, 1991. Fascinating study of the modern movement against drunk driving, with special attention to such grassroots movements as Mothers Against Drunk Driving.

Taylor, Lawrence E., and Steven Oberman. Drunk Driving Defense. New York: Aspen, 2003. How-to guidebook written by a lawyer to help people beat drunk-driving charges. While the ethics of publishing such a book may be questionable, the book provides revealing insights into the problems of prosecuting drunk driving offenses.

Watson, Ronald R., ed. Alcohol, Cocaine, and Accidents. Clifton, N.J.: Humana Press, 1995. Collection of ten research papers on the roles of alcohol and cocaine in motor vehicle, aviation, and aquatic accidents that are addressed to policymakers and people in law enforcement. Particular attention is given to the behavior of young people.

"What If You Refuse a Field Sobriety Test?" Alchohol.org, 25 Oct. 2022, alcohol.org/dui/field-sobriety-test/. Accessed 10 July 2024.

Wilson, R. Jean, and Robert E. Mann, eds. Drinking and Driving: Advances in Research and Prevention. New York: Guilford Press, 1990. Interdisciplinary collection of articles on a wide variety of aspects of drunk driving. The first section covers efforts to understand impaired drivers, the second section examines efforts to deter drunk driving, and the third section examines other preventive measures.