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The Drug Recognition Expert: Combating Drugged-Driving and More

By: Thomas Page, Drug Recognition Expert Emeritus

The Drug Recognition Expert (DRE) program, procedure, and police officers constitute a systems approach to identifying, apprehending, and prosecuting the individual who drives while under the influence of a drug or drugs.  The program and procedures were initially developed in the mid-1980s by Los Angeles, California, Police Department (LAPD) traffic enforcement officers.  A primary impetus for the development of the DRE was the recognition that drugs, in addition to, or other than alcohol, impaired many drivers.

Drug Recognition Expert officers have specialized training

Drug Recognition Expert officers, commonly referred to as DREs, have specialized training and develop skills in observing, documenting, and interpreting clinical and behavioral signs and symptoms of drug influence. In many United States courts the DRE officer is allowed to state an expert opinion about an individual’s ability to safely operate a vehicle. In February of 2017, the Supreme Court of Canada ruled that a DRE’s testimony could be introduced in court without a challenge to the DRE’s qualifications as an “expert.” Further, the DRE officer may be allowed to state an opinion as to the specific drug or drugs, based on categories, that the person is impaired by.

Although jurisdictions frequently define “under the influence” differently, generically under the influence means that a person’s ability to safely operate a vehicle has been decreased as a result of the presence of a drug(s). Thus, driving while fatigued is not “under the influence,” whereas driving after taking a sleep-inducing medication can be, if the driver is impaired.

Classically, a different officer, an arresting officer, who has determined at roadside that a driver is impaired, requests the DRE and that drugs may be responsible (in total or in part) for the individual’s impairment. The arresting officer will typically have administered the Standardized Field Sobriety Test battery to the individual as part of a pre-arrest screening process. Usually, the DRE is requested to assist in the investigation subsequent to an alcohol-breath test.  Simply, the person may appear to be more impaired than the alcohol reading accounts for.

The Drug Recognition Expert Procedure

The DRE is responsible for making three determinations: (1) that the person is in fact impaired and that the impairment is not consistent with the alcohol reading, if any; (2) determine if the impairment may be caused by a medical condition, that may require assessment or treatment; (3) determine the category (or categories) of substances responsible for the impairment.

In order to reach these three determinations, the DRE utilizes a 12-step procedure, sometimes (inaccurately) called a “protocol,” administered in a controlled environment such as a police station, which results in an opinion. If the opinion is that the person was under the influence at the time of driving, the individual is usually required to provide a blood sample that a toxicology laboratory tests for certain drugs and/or metabolites.  The prosecutor may delay a prosecution decision until the laboratory results have returned.

Drug Recognition Expert
The DRE is responsible for making three determinations

Briefly, the DRE 12-step procedure begins and ends with toxicology. The first step is a breath test for alcohol. The last step is the analysis of the biological specimen, usually blood, for drugs.  Steps two through eleven include an assessment of the individual’s vital signs, including blood pressure, pulse rate (taken three times during the assessment), and body temperature. In addition, DREs assess the person’s pupil sizes in various light levels, reaction to light, as well as assessing the person for Horizontal Gaze Nystagmus (HGN). HGN, which is a gaze-evoked jerky movement of the eyeball, is caused by a number of different drugs, primarily alcohol and other Central Nervous System Depressants.  Medical doctors have compared the 12-step procedure to a physician’s getting a patient’s history and physical.

The drugs of abuse that DREs are concerned with are substances, whether designed to be used as drugs or not, that in small amounts, alter mood or behavior. These substances have a primary effect on the Central Nervous System (CNS). which consists of the brain, brainstem and spinal cord. A substance that does not affect the CNS may be misused (such as taking an antibiotic drug for a virus, a cold) but is not used for mood-altering effects.

The Categories of Drugs

DREs use a seven-category schema, which classifies drugs based on a shared pattern of detectable effects, rather than a classification system based on legality, or chemical make-up.  The substances within a category have similar effects. Generally, if an individual is tolerant to one of the drugs in the category, he/she will be tolerant to the other drugs. And probably most relevantly, if an individual is unable to obtain his/her drug of choice in a category, another drug from that category may be substituted.  A current, and classic, example of this is what is occurring with heroin, fentanyl, and oxycodone.  It was no surprise to Drug Recognition Experts that heroin use increased dramatically in response to a crackdown on the prescribing of legitimate pharmaceuticals, such as OxyContin.

The seven drug categories are:

Central Nervous System Depressants

Alcohol is the prototypical CNS Depressant. The other substances in this category have effects – at intoxicating levels – similar to alcohol. Of course, the other substances lack the odor of alcoholic beverages, and will not register in a breath test for alcohol. Some examples are: Benzodiazepines, such as zolidem (Ambien), alprazolam (Xanax), Valium, Barbiturates, seizure control medications, muscle relaxants, and anti-anxiety tranquilizers.


This category takes its name from the primary method of administration: breathing the fumes. Volatile solvents, such as gasoline, toluene, kerosene, and many others fall into this category. Nitrous oxide, commonly known as laughing gas, has legitimate medical uses as an anesthetic, but is also frequently abused.

Drug Recognition Expert
7 Categories of drugs include legal and illegal drugs

Dissociative Anesthetics

This category was formerly named Phencyclidine (PCP) and its analogues. With the popularity of drugs such as (DXM) dextromethorphan, and the realization that the effects of DXM in large amounts mirrors that of PCP, the name of the category was changed to better reflect the reality of abuse. The drug Ketamine also belongs to this category. PCP and Ketamine have a variety of legitimate medical uses, including as surgical anesthetics on humans and animals.


Marijuana, in its various forms, is the primary drug in this category. Pharmaceutical preparations, such as Dronabinol (synthetic THC), and the cannabinoid receptor mimetic drugs, frequently, but incorrectly, called “synthetic cannabis,” also are included in this category.

Central Nervous System Stimulants

The stimulants are sympathomimetic substances such as cocaine or methamphetamine. Their effects mimic the body’s fight or flight response to danger. Except that the “danger” may be chemically induced, rather than based in reality. Cocaine, methamphetamine, and many other substances belong to this category.


The drugs in this category are used primary for their hallucinogenic, or sensory distortion, effects. LSD, psilocybin mushrooms, and MDMA, commonly known as “Molly” or “Ecstasy,” are in this category.

Narcotic Analgesics

These are the opioids, the opiate and opiate-like substances. Be definition these are sedation-producing pain relievers, or analgesics. Heroin, morphine, methadone, fentanyl and many other pharmaceutical preparations, such as oxycodone, are included.

The Curse of Alcohol in Understanding Drugs

The blessing and curse of alcohol

It’s been called the blessing and the curse of alcohol in understanding the effects of non-alcohol drugs.  A key difference is that there are legally prohibited levels of alcohol as it pertains to driving. That legal level (actually an illegal level) is .08%. Of course, that doesn’t mean that the individual is sober, unimpaired at a .079% level. The establishment of a per se level for alcohol is a legislative decision that’s based partly on science, on studies of impairment, but also on balancing the unique role of alcoholic beverages in society.  A common question regarding drugs – asked by judges, attorneys, jurors – is how much of a drug does it take to reach the equivalent of an .08% alcohol level.  “How much marijuana can someone smoke before they are impaired equivalently to an .08%?”  And therein lies the conundrum! We expect that what occurs with alcohol will apply to other drugs, failing to appreciate the fact that alcohol is the exception and not the rule!

The pharmacokinetics of alcohol is very different than other drugs. Alcohol is taken into the body, and then somewhat consistently over time is metabolized and excreted out. As a result, if a person achieves a level of .10%, it will take about 6 hours of non-drinking to return to 0.  And if a person has a .20% level, it will take twice as long, 12 hours. (These are strictly approximations for demonstration purposes.) Drugs are different!  One can’t double the dose of heroin, of cocaine, of marijuana, and on and on, and be “high” for twice as long. Simply, the pharmacokinetics (the ins, arounds, changes, and outs of drugs) are different for drugs other than alcohol.  Currently, legislatures around the United States are struggling with establishing per se levels for cannabis (think marijuana). Some have adopted a “zero tolerance” approach in which a driver can’t have any THC in the body, whereas others have adopted a 2 ng/ml or a 5 ng/ml – in the blood – levels. There are many problems with this approach. Blood testing measures what’s in the blood, and not what might be in the brain. Since marijuana is lipophilic, it can store for long periods of time in the fat of the body, such as the brain. As a result, the impairment may be increasing while the blood level is decreasing. It is a conundrum indeed. How would a person know that he/she has a blood level in excess of a statutory per se level of 2 ng/ml? I suspect that most people don’t even know what a nanogram is. (It’s a billionth of a gram!) Does a per se law in effect say that it’s OK to drive after using marijuana as long as you’re not impaired, and that your level is below 2 billionths of a gram in a milliliter of your blood?  That’s one of the problems with the non-alcohol drugs.

Unfortunately, poly-drug use is the rule these days. That means that people use more than one drug at the same time, or serially. The effects of one drug may reinforce the effect of another, may partially mitigate the effects, may prolong, or may add on entirely new effects.  Certainly, however, one drug will not cancel out the effects of the other, no more than drinking coffee (a mild stimulant) will cancel out – make sober – the alcohol-impaired individual.

Drug Recognition Expert
It’s more than drugged driving.

It’s More Than Drugged Driving

While the primary focus of DRE training is Driving Under the Influence (DUI) enforcement, the knowledge and skills mastered by DREs have applicability to many other fields, including drugs in the workplace, assessment of the accuracy of witness reports, domestic violence, child abuse, transportation and delivery of drugs, including controlled substances, and countless more.  In addition, DRE-related training has been provided to medical professionals, including occupational nurses, physicians, psychiatrists, psychiatric technicians, social workers and public health professionals.  DRE expertise may be helpful whenever drug-influence is at issue.

Since its humble beginnings in Los Angeles nearly forty years ago, the DRE program has grown to include DRE officers in all 50 U.S. States, all Canadian provinces, and a number of other countries.  The International Association of Chiefs of Police now recognizes over 7,000 officers as DREs. These dedicated and highly skilled officers are making our roads safer by identifying and apprehending the drug-impaired driver.

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