National District Attorneys Association
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Impaired Driving

Every year, impaired drivers are responsible
for killing thousands of innocent people on
America’s highways. Close to 1.5 million arrests
are made annually, comprising more than ten
percent of the total number of arrests made
each year.

Impaired driving prosecutions are some of the
most highly litigated and contested cases
within the criminal justice system. The
National Traffic Law Center supports
the efforts of state and local prosecutors
and other traffic safety professionals in dealing with challenges to the use of breath test instruments, alcohol and drug toxicology, standardized field sobriety testing and more by providing technical assistance and legal resources. Likewise, when faced with additional inquiries about getting impaired drivers off the road, NTLC provides information concerning the effectiveness of administrative license revocation, ignition interlock systems, sobriety checkpoints and much more.

Hardcore Drunk Driving Video
Law enforcement, prosecutors, judges, probation and parole, and treatment providers all play an important role in the swift identification, certain punishment, and effective treatment of the hardcore drunk driver. The National Traffic Law Center is proud to present its Hardcore Drunk Driver prosecutorial training in video format courtesy of The Century Council.  

Horizontal Gaze Nystagmus (HGN)
Horizontal Gaze Nystagmus (HGN) is the most reliable of the standardized field sobriety tests available for law enforcement officer to use when encountering an impaired driver. It refers to a horizontal jerking when the eye gazes to the side. In the impaired driving context, alcohol consumption or consumption of certain other central nervous system depressants, inhalants or phencyclidine, can cause the jerk or bounce associated with HGN. An HGN examination requires a suspected impaired driver to follow the movement of a stimulus with their eyes. Officers look for three clues in each eye: Lack of smooth pursuit; sustained and distinct nystagmus at maximum deviation; and onset of nystagmus prior to a 45 degree angle of onset.

Horizontal Gaze Nystagmus The Science and The Law: A Resource Guide for Judges, Prosecutors, and Law go to link

Nystagmus Testing in Intoxicated Individuals  go to link
Citek, K, Ball, B, and Rutledge, DA, Optometry 2003; 74-695-710. © 2003 by the American Optometric Association. Reprinted with permission.


Breath Testing
Evidential Breath Testing Devices

Conforming Products List go to link


Ignition Interlock
An ignition interlock device is a valuable tool in the efforts to combat alcohol impaired driving. To operate a vehicle equipped with an ignition interlock device, the driver must first provide a breath sample. If the breath sample has an alcohol concentraion that exceeds a predetermined level, the vehicle will not start. To prevent subsequent drinking, periodic and random re-tests are required.

Ignition Interlock — What You Need to Know: A Toolkit for policymakers, highway safety professionals and advocates go to link


Drug Evaluation and Classification
Drug Recognition Experts are police officers specially trained to recognize impairment in drivers under the influence of drugs other than, or in addition to, alcohol.

The Drug Recognition Expert (DRE) Response to the Drug Impaired Driver:
An Overview of the DRE Program, Officer, and Procedures
by Thomas E. Page
Download article go to link
American Bar Association Resolution on DRE go to link
<empty> A list of the Drug Evaluation and Classification validation studies go to link
Drugs and Human Performance Fact Sheets go to link
More information on the International Drug Evaluation and Classification Program go to link


Results of the 2007 National Roadside Survey
of Alcohol and Drug Use by Drivers
go to link

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