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References on Drugs and Driving

Study of a Drug Recognition Expert (DRE) Program

M Burns*, EV Adler**

* Southern California Research Institute, 11914 W. Washington Boulevard, Los Angeles, CA 90066, USA

** Crime Laboratory, Arizona Department of Public Safety, USA


The Drug Influence Evaluation (DIE) is a systematic, standardized 12-step method. It yields information which is the basis for a DRE-trained officer's opinion (1) that a suspect is/is not impaired, (2) if impaired, that the impairment is/is not drug related, and (3) if drugs, that a specific drug category (or categories) is present.

DIE records and toxicological analyses of urine and blood specimens from 500 suspected drug-impaired drivers were analyzed with data base software, which had been developed specifically for analysis of DRE data. The records were the 53-month work product of the Phoenix Police Dept. DRE unit. DRE opinions about suspect's drug impairment and identifications of drug categories were highly accurate.

The Arizona Dept. of Public Safety Crime Laboratory reported finding 813 drugs in 416 specimens; 68 specimens contained no drug and 16 arrestees refused to provide a specimen. Officers identified at least one drug in 91% of the positive specimens. Specimen analysis confirmed or partially confirmed 83.5% of DRE drug identifications. It is concluded that the DRE program utilizes a valid method for detecting and classifying drug impairment.


Police officers' duties include the detection and arrest of drivers who cannot safely operate their vehicles. In the case of alcohol-impaired suspects, the measurement of breath alcohol concentration (BrAC) provides immediate support for the officers' arrest decisions. When the BrAC is zero or low and chemical tests for other drugs (i.e., analysis of blood and urine specimens) are obtained, the results are both less timely and less informative.

Results from the analysis of urine specimens, which may not be available for days-to-weeks after a sample is obtained, can provide evidence that some unknown amount of drug was used at some unspecified time prior to the arrest. The positive finding falls short, however, of demonstrating conclusively that the parent drug was present in the blood and affecting the driver at the time of driving.

A positive blood drug concentration is more definitive evidence of possible impairment, but again the analytic results are not available to the officer at the time of an arrest decision. To further complicate the issue, the relationship of drug concentration and driving impairment remains unknown for many potentially impairing substances.


The problem of identifying drug impaired drivers led officers within the Los Angeles Police Department, aided by scientists, physicians, and other drug experts, to develop a drug recognition training program. With the objective of training officers to recognize behaviors and physiological states associated with psychoactive drugs, a training curriculum evolved over time, attracting the attention of other agencies who were experiencing similar problems. At the present time, DRE training is available for qualified agencies nationwide under the auspices of the National Highway Traffic Safety Administration, U.S. Department of Transportation.

The DRE evaluation, which is requested by an arresting officer when a suspect's BAC is inconsistent with his driving and behavior, includes 12 steps. (Student Manual, 1991) Based on the evaluation, the DRE forms an opinion as to 1) whether the suspect is impaired, 2) if impaired, whether the impairment is related to drugs, and 3) if related to drugs, which drug category or combination of categories is causing the impairment.

The primary DRE activity is reliable identification of drug-impaired drivers. In addition to this service to the agency and the community, there also is evidence that the program has an effect on drug trafficking and general crime suppression. These positive outcomes, however, are not without cost. The program places high demands on a police department for both officer training and duty time. Also, the increased number of specimens may tax the resources of the laboratory. Rigorous evaluation of program benefits is needed.

A study funded by the Arizona Governor's Office of Highway Safety examined the records of the Phoenix Police Department (PPD) DRE program (Adler & Burns, 1994). Data base software (NIDABASE) developed by the Southern California Research Institute under National Institute on Drug Abuse funding was used to record and analyze the records (Burns, 1990).


A DRE follows a systematic and standardized protocol to examine a driver suspected of being impaired by a drug(s). He records his observations and opinion on a Drug Influence Evaluation (DIE) form. In Phoenix, urine specimens are analyzed by the Arizona Department of Public Safety (AZ-DPS) Central Regional Laboratory. Results are recorded as a Scientific Examination Report (SER).

The two documents, DIE forms and SERs, were analyzed for 500 drivers (392 men, 108 women). Another 27 records were incomplete and unusable. These cases are the work product of the PPD DRE program for the 53 month period, January 1989 through May 1993.


The drugs or metabolites confirmed in urine specimens are summarized in Tables 1 and 2.

Table 1
Drugs or Metabolites Confirmed in Urine Specimens

Drugs (number) Specimens (number)
0 68
1 163
2 or more 253
Total Tested 484
Refusals 16
Grand Total 500

Table 2
Drugs or Metabolites Confirmed in Urine Specimens

Drug Number
Marijuana 165
Coc/BE 115
Benzo. 108
Morphine 71
Methamp. 69
Codeine 65
Barbit. 35
PCP 22
Amphet. 18
Total 668
Other 145
Grand Total 813

Almost 84% of the arrestees were Caucasian, 10% were Hispanic and 6% were black. They were predominantly young adult males. Men were most frequently in the 20-29 year age range. Women were slightly older.

Together, a DRE evaluation and analysis of a specimen identify unimpaired as well as drug-impaired drivers, as illustrated in Table 3.

Table 3
Outcomes of Comparisons between DRE Opinion and Laboratory Tests

DRE Opinion Scientific Examination Report
Drug Found (+) Drug Not Found (-)

A "Hit", Cell 1, occurs when the DRE's opinion that a drug is present is confirmed by the laboratory. A "False Positive (FP)", Cell 2, occurs if the DRE believes a drug is present, but it is not confirmed by the laboratory. If a DRE does not predict a drug, which subsequently is found in urine, the decision is a "False Negative (F.N. or Miss)", Cell 3. Finally a "Correct Rejection (C.R), Cell 4, occurs if the SER corroborates an opinion that a drug was not present.

DREs correctly identified at least one drug category in 378 (91%) of the 416 specimens for which the laboratory confirmed one or more drugs (Table 4). No drugs were found in specimens from 26 individuals who the DREs judged not impaired by drugs. The DRE decisions were supported for 404 (83.5%) of 484 specimens, and were not supported for 80 (16.5%).

Table 4
DRE Identifications of Drugs (s)

Classification Numbers
HIT 184    
HIT + F.P. 56    
HIT + F.N. 115    
HIT + F.P. + F.N. 23    
FALSE NEG. + F.P. 24    

Failure to identify a drug-impaired driver risks serious consequences and, therefore, "misses" require close examination. In 115 cases in which a DRE correctly identified one or more drugs by category, he/she failed to identify others which were present in the specimens. In 14 cases, the DRE entirely missed the drug(s) found in urine. In 47 of the specimens for which the laboratory confirmed multiple substances, DRE decisions were combinations of hits, false positives, and false negatives.

DREs missed marijuana more often than other drug categories, but it cannot be determined whether the misses were DRE error or a consequence of the drug's time course. Since the drug's principal metabolite can be detected in urine for days-to-weeks, a specimen may test positive even though it was obtained at a time when active marijuana was not present. A marijuana positive in urine, if not supported with evidence of behavioral impairment, does not speak to the question of drug influence.

Cocaine false negatives, or misses, occurred with the second highest frequency. Behavioral signs of stimulants often are difficult to detect, but again it cannot be determined with certainty whether the misses are true errors. The half-life of cocaine is approximately 90 minutes but benzoylecognine (BE), a metabolite with no psychoactive effects, can be detected in urine for 24-48 hrs. A urine positive for cocaine indicates that BE was confirmed in the specimen but does not demonstrate that a suspect was under the influence during the evaluation.

A miss is a failure to observe the signs and symptoms of drug impairment. That may occur as DRE error. It may occur because one substance produces severe symptoms, which entirely mask the symptoms of other drugs. It may also occur when a parent drug has been eliminated from the body but an inactive metabolite remains. In the latter case, the laboratory will report a positive finding and the DRE scores a "miss" although the opinion of no drug impairment was correct.

A DRE may also err by concluding incorrectly that a driver is drug impaired. In the PPD data, the DREs appear to have been incorrect 42 times when they believed a drug was causing impairment. Such "false positives" occur as errors of observation and interpretation. Less frequently they occur when the DRE is correct, but the laboratory fails to confirm the drug due to limitations of analysis.

The criterion by which a DRE opinion is judged is, in most cases, the presence of a drug or its metabolite in blood or urine. Occasionally, that criterion leads to the appearance of DRE error when, in fact, no error occurred. The number of times that occurs cannot be determined in retrospective data analysis.


Findings from a study of 500 DIE and SER records support the validity of drug recognition methods. DRE opinions about drug-impairment were largely confirmed by analysis of urine specimens. The study demonstrates the information that can be gleaned from the analysis of the records which reside in DRE files nationwide. At the present time, those records are largely unanalyzed.


Adler, E.V. amd Burns, M. Drug Recognition Expert (DRE) Validation Study. Final Report to Governor's Office of Highway Safety, 1994, Arizona Department of Public Safety. 93 pp.

Burns, M. (1990) Development and Pilot Test of a Computer Data Base of Drug Evaluations of Impired Drivers. Final Report, National Institute on Drug Abuse Order 89M079578301D.

Student Manual, 1991 Edition, Drug Evaluation and Classification Training Program, The Drug Recognition Technician School, NHTSA, U.S. Dept. of Transportation, 1991.


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