The Drug Recognition Expert (DRE) protocol is a standardized, systematic procedure used by specially trained law enforcement officers to detect and identify impairment in drivers suspected of operating a vehicle under the influence of drugs. This protocol provides a method for determining if a person’s observed impairment is due to a medical condition, alcohol, or other drugs. The core function is to connect observable signs and symptoms to a specific category of psychoactive substance. The DRE evaluation is requested when a driver shows impairment signs that are not fully explained by their measured blood alcohol concentration.
Defining the Role and Goal of the DRE
An officer must complete a multi-phase training and certification process to become a certified Drug Recognition Expert. This training includes extensive academic coursework, often totaling around 72 hours, covering pharmacology, physiology, and the effects of the seven different drug categories on the human body. Following the classroom portion, a candidate must complete a field certification phase, which requires conducting a minimum of 12 supervised evaluations on impaired subjects. The expert status is confirmed only after the candidate achieves a toxicological confirmation rate of at least 75% for the drug categories they identify. The primary goal of this assessment is to differentiate impairment caused by drugs from impairment due to a physical injury or an underlying medical issue, such as a seizure or stroke.
The Standardized 12-Step Evaluation Process
The DRE protocol is a 12-step process that is separated into three distinct phases for a systematic assessment of the driver. The evaluation begins with an interview of the arresting officer and a review of the subject’s breath alcohol test results to rule out alcohol as the sole cause of impairment. The DRE then conducts a preliminary examination to check for signs of a medical condition or injury that might be causing the impairment.
The second phase involves a series of divided-attention psychophysical tests, similar to the Standardized Field Sobriety Tests (SFSTs), which assess the subject’s balance, coordination, and ability to follow instructions. These tests, which include the Walk and Turn and the One-Leg Stand, evaluate the subject’s ability to divide their attention between a mental and physical task. Performance on these tests helps the DRE determine if the central nervous system is affected.
The third and most detailed phase consists of clinical and physiological assessments, which involve checking vital signs and conducting specific eye examinations. The DRE checks the subject’s pulse, blood pressure, and body temperature, looking for measurements outside the expected normal range. A comprehensive eye exam is performed, including checking for Horizontal Gaze Nystagmus (HGN) and Vertical Gaze Nystagmus (VGN)—involuntary jerking of the eyes—and measuring pupil size under three different lighting conditions using a pupilometer. The DRE also assesses the subject’s skeletal muscle tone, which can appear rigid or flaccid depending on the category of drug involved. The final steps include a full body check for evidence like injection sites, which may indicate recent drug use.
Classifying Impairment and Legal Implications
Upon completing the 12-step evaluation, the DRE uses the collected data and a specific drug matrix to form an expert opinion on the subject’s impairment. This opinion identifies whether the subject is impaired and, if so, which of the seven categories of drugs is the likely cause. These categories include Central Nervous System (CNS) Depressants, CNS Stimulants, Hallucinogens, Dissociative Anesthetics, Narcotic Analgesics, Inhalants, and Cannabis. The DRE’s analysis relies on specific physiological indicators, such as characteristic changes in pupil size, blood pressure, and muscle tone, associated with each drug category. The expert opinion, which details the observed signs and the corresponding drug category, is then documented and used as evidence in court proceedings related to impaired driving. Although the DRE test strongly suggests a drug category, it does not confirm the exact substance; a subsequent toxicological sample, such as blood or urine, is typically required to confirm the presence of the identified substance.