Drug Recognition Experts

A Drug Recognition Expert (DRE) is a law enforcement officer who administers tests on suspected impaired drivers to attempt to determine whether the individual is impaired and if so, to categorize the type of impairing substance. Law enforcement officers become DREs by completing a three phase course. DREs are trained to follow a 12-step protocol.

DRE testimony is used to prosecute cases of suspected drugged driving because of the limitations of toxicology testing. Blood tests may detect the presence of a substance, but the tests used do not measure the quantity of substance ingested or whether amount of the substance is sufficient to cause impairment in an individual. Thus, the testimony of a DRE is often needed to show impairment.

Challenging Admissibility

Rule 702(a1) was enacted in 2006 by the General Assembly of North Carolina and addresses the admissibility of testimony by a DHHS-certified DRE. Rule 702(a1) requires proper foundation and that the witness be qualified under the standard requirements for expert testimony, as set forth in Rule 702(a).

The Court of Appeals has interpreted the provision of (a1) that deals with the admissibility of HGN evidence to require the proponent of the witness to demonstrate that the witness is qualified as an expert by knowledge, skill, experience, training, or education, but not to demonstrate that the HGN testing method is sufficiently reliable. State v. Smart, 195 N.C. App. 752 (2008). In light of State v. Smart, it seems that challenges related to the reliability of the DRE protocol would go to the weight of the evidence, not its admissibility, while challenges to the particular DRE officer's knowledge, skill, experience, training, or education may go to admissibility. However, it may be worthwhile to question the weight that should be given to the DRE evaluation given significant problems that have been identified with the technique. Attorneys should also consider whether the recent amendment to Rule 702(a) which adopts a new standard for the admissibility of expert testimony that was not in place when the 2006 changes were enacted affects the admissibility of this testimony.

Attorneys may also consider moving to limit the scope of the testimony of the DRE. Rule 702(a1) allows a DRE to testify regarding "[w]hether a person was under the influence of one or more impairing substances, and the category of such impairing substance or substances." Testimony regarding the effects of drugs on the body and on impairment requires expertise in the fields of pharmacology, toxicology, and/or medicine. This type of testimony would exceed the scope of admissible testimony contemplated by Rule 702(a1). Additionally, in cases where the DRE did not personally examine the defendant, the witness would not be able to offer testimony regarding impairment without qualifying as an expert in pharmacology.

Challenging a Drug Recognition Expert's Qualifications

When challenging a DRE's qualifications, counsel should consider these areas:

  • Does the DRE have medical training that renders him qualified to evaluate a suspect's physiological symptoms? The DRE evaluation is considered a diagnostic examination.
  • The DRE protocol requires the DRE to make a medical diagnosis during the examination by ruling out medical conditions. What training does the DRE have regarding distinguishing effects of drugs from other medical conditions?
  • How well did the DRE do in the training course? What continuing education has he had? International Association of Chiefs of Police standards require recertification every two years. See the NC Forensic Tests for Alcohol Drug Recognition Experts Requirements for additional training requirements.
  • On the DRE certification exam, an officer can identify impairment by multiple substances and if the subject is impaired by any of the substances identified, the answer is deemed correct. How many substances did the officer incorrectly identify on the qualification test?
  • What is the DRE's track record? DREs are required to maintain a "Progress Log" and a "Rolling Log" of all drug influence evaluations.
  • Did the DRE deviate from the protocol? The DRE protocol requires the measurement of the suspect's blood pressure and temperature twice and measurement of pulse three times; dark room examinations of the suspect's eyes; examination of skeletal muscle tone; a toxicological examination; and other examinations. The protocol requires that an opinion be based on a complete administration of all 12 steps.
  • What is the minimum number of indicators that a DRE needs to reach an opinion of impairment? Does the DRE believe there is a standard set by the DEC program regarding minimum number of indicators or does each DRE determine his/her own minimum?
  • Does a determination that the defendant was affected by drugs mean that the defendant's driving was impaired?
  • The DRE protocol is considered a "diagnostic examination" in which the DRE to "evaluates and assesses the person's appearance and behavior;...measures and records vital signs and makes precise observations of ther person's automatic responses and reactions; [and]...administers carefully designed psychophysical tests to evaluate the person's judgment, information processing ability, coordination and various other characteristics." If the DRE does not personally conduct the examination, but instead relies on another officer's notes, is it possible to complete these evaluations?

Challenging the Reliability of the DRE Protocol

Law enforcement agencies have attempted to demonstrate the reliability of the DRE protocol through research; however, these studies indicate a high rate false positives and the misidentification of impairing substances. Attorneys should consider whether these studies were conducted using appropriate research protocols including use of a double-blind research design, use of a contol group, use of relevant dosages of impairing substances, use of appropriate statistical analysis to assess the relevance of the results, and whether the research was peer reviewed.

  • The Heishman Study I, Heishman Study II, the Shinar and Schectman Study are peer reviewed and published studies on the subject of the DRE protocol. These studies indicate high rates of misidentification of substances and false positives.
  • Drug Recognition Expert (DRE) Validation Study - a 1994 study by Eugene Adler of the Arizona Department of Public Safety and Marcelline Burns of the Southern California Research Institute. The study suggests that lab tests failed to find any drug present in 16.4% of case samples where DREs identified drug impairment (p. xi). This figure does not reflect the number of cases where DREs determined impairment and the suspect had a controlled substance present in his blood, but not a sufficient amount to cause impairment.
  • Field Evaluation of the Los Angeles Police Department Drug Detection Procedure - a 1986 study by the US Department of Transportation on the rate of correct impairment identification by DREs. In 49% of the cases, the DREs correctly identified every controlled substance found in a toxicology screening (p. 16). This study did not measure the number of cases where DREs determined impairment and the suspect had a controlled substance present in his blood, but not a sufficient amount to cause impairment.
  • See State v. Sampson, 167 Ore. App. 489 (2000) for a discussion of research regarding the error rate of DRE evaluations.

Case Law

In State v. Wright, No. COA09-1062, 204 N.C. App. 212 (May 18, 2010) (unpublished) and State v. Blinderman, No. COA08-824, 197 N.C. App. 402 (2009) (unpublished) courts held that where the defendant failed to object at trial to the testimony of the DRE, admission of the testimony did not rise to the level of plain error.

See Burton v. Kentucky, 300 S.W.3d 126 (Ky. 2009) where the court found that testimony from a DRE was improper where the DRE did not personally observe the defendant but instead based his opinion on review of records.

The Circuit Court for Carroll County, Maryland recently held that DRE evidence should be excluded. The court held that identification and classification by DREs "is not generally accepted as valid and reliable in the relevant scientific community." See the opinion for a summary of expert testimony regarding DRE examinations which raises questions about the accuracy of and use of the drug matrix, the diagnosis of nystagmus, an officer's ability to diagnose medical conditions, the lack of peer reviewed scientific studies of the DRE protocol, and misinformation in the DEC manual regarding drug categories and drug effects on the body. The court found that the "DRE Protocol fails to produce an accurate and reliable determination of whether a suspect is impaired by drugs and by what specific drug he is impaired" and that the "DRE training program does not enable DREs to accurately observe the signs and symptoms of drug impairment, therefore, police officers are not able to reach accurate and reliable conclusions regarding what drug may be causing impairment." State of Maryland v. Charles David Brightful, et al, No. K-10-04-259, Circuit Court for Carroll County, MD March 5, 2012. See The Truth About Forensic Science for Attorney Justin McShane's analysis of this case.

Other Resources

To view copies of the DRE Student and Instructor Manuals, visit the Washington State Patrol Forensic Laboratory Services website.

Expert Testimony Regarding Impairment - the UNC School of Government's Shea Denning discusses the adoption of Rule 702(a1) and the admissibility of HGN and DRE evidence. For additional information, contact Shea Denning. She is available as a resource on this topic.

A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid - Psychopharmacology (Berl). 2012 October; 223(4): 439-446. This study finds that Standardized Field Sobriety Tests are only mildly sensitive to impairment from cannabis in heavy users. THC produced impairment on SFST performance in 30-50% of participants.

Do Delta9-Tetrahydrocannabinol Concentrations Indicate Recent Use in Chronic Cannabis Users? Addiction. 2009 December: 104(12):2040-2048. This study finds that THC concentrations persist in whole blood multiple days after drug discontinuation in heavy chronic cannabis users.

An Overview of the DRE Program, Officer, and Procedures - an overview of the DRE Unit of the Los Angeles Police department, where the DRE program was developed. There is a section on Laboratory and Field Evaluation of the DRE program which summarizes various studies on the efficacy of DREs determinations.

The Drug Evaluation and Classification Program: Targeting Hardcore Impaired Drivers - a National Traffic Law Center/American Prosecutors Research Institute 2004 publication. There are sections explaining DRE training, protocol, and drug categories. See p. 8 for a discussion of the accuracy and reliability of the DRE program. See p. 9 for the admissibility of scientific evidence and DRE evidence. As the publication is targeted to prosecutors, there are descriptions of common defense challenges to the protocol (pp. 13-14).

Priorities and Strategies for Improving the Investigation, Use of Toxicology Results, and Prosecution of Drug-Impaired Driving Cases - a 2004 National Highway Traffic Safety Administration (NHTSA) publication targeted to prosecutors. The first section details some of the major problems with prosecuting drug impaired driving cases, such as the lack of any clear correlation between blood drug concentrations and impairment for many drugs (p. 8).

Drug Symptom Matrix - this chart shows the seven classes of drugs that DREs attempt to identify and the symptoms DREs look for to determine impairment.