What Does a Drug Recognition Expert (DRE) Actually Do?
A Drug Recognition Expert does considerably more than administer field sobriety tests. The DRE process is a standardized, multi-step evaluation designed to assess suspected drug impairment.
In a suspected drug DUI case, an officer may write: "A DRE was requested."
For someone unfamiliar with drug-impaired driving investigations, that can sound like the officer simply called a more experienced DUI investigator.
A Drug Recognition Expert, or DRE, has specialized training in evaluating suspected drug impairment.
The DRE process goes considerably beyond ordinary roadside field sobriety testing.
It is intended to be a systematic evaluation combining observations, psychophysical testing, eye examinations, vital signs, physical findings, interviews, and toxicological evidence.
Understanding that process is essential to understanding a drug DUI case.
Why Are DREs Used?
Alcohol is comparatively easy for law enforcement to screen for.
A breath-testing device can detect alcohol and produce a numerical result relatively quickly.
Most drugs do not work that way.
There is no single roadside breath number that tells an officer whether someone is impaired by cannabis, methamphetamine, a benzodiazepine, an opioid, or another drug.
Drug impairment can also look very different depending on the substance involved.
A stimulant may produce a different physiological picture than a central nervous system depressant.
Cannabis may produce different findings than a narcotic analgesic.
The DRE program was developed to provide officers with a more structured method for evaluating those cases.
The DRE Evaluation Is a Process, Not One Test
People sometimes refer to the "DRE test."
That description is misleading.
The DRE evaluation is a multi-step process.
The standardized process includes components addressing:
- Breath alcohol
- Information from the arresting officer
- Preliminary medical and impairment observations
- Pulse measurements
- Eye examinations
- Divided-attention psychophysical tests
- Vital signs
- Pupil size under varying lighting conditions
- Examination of the nasal and oral cavities
- Muscle tone
- Possible evidence of drug administration
- Statements and questioning
- The DRE's opinion
- Toxicological evidence
The value of the DRE process comes partly from the idea that these observations should be considered together rather than relying on one isolated sign.
DREs Evaluate Drug Categories
A DRE generally does not begin by trying to identify an exact pharmaceutical compound from observation alone.
The program organizes drugs into broad categories based on their expected effects.
Those categories include substances with different central nervous system and physiological effects.
The DRE compares the person's observed signs and symptoms with patterns expected from the suspected category or categories.
That is why internal consistency matters.
If the officer identifies a particular drug category, the findings documented during the evaluation should make sense in relation to that opinion.
Eye Examinations Are Important
Eye examinations play a significant role in the DRE process.
Depending on the suspected drug category, the DRE may evaluate:
- Horizontal Gaze Nystagmus
- Vertical Gaze Nystagmus
- Lack of Convergence
- Pupil size under different lighting conditions
Different drug categories have different expected effects.
For example, HGN is associated with some categories but is not expected simply because a person has used any impairing substance.
That makes correct administration and drug-category interpretation important.
An officer should not treat every abnormal eye observation as generic proof of "drug impairment."
Vital Signs Add Another Layer
DRE evaluations can include measurements such as:
- Pulse
- Blood pressure
- Body temperature
Again, those observations are interpreted as part of a pattern.
Some drugs may be associated with elevated physiological activity.
Others may be associated with depressed physiological activity.
But an isolated abnormal vital sign does not uniquely identify a drug.
Stress, illness, environment, physical activity, medication, and individual physiology can also matter.
The evaluation has to be considered as a whole.
What About the Walk-and-Turn and One-Leg Stand?
DREs also use divided-attention tests.
These can include familiar SFST components such as the Walk-and-Turn and One-Leg Stand, as well as additional psychophysical tasks within the DRE protocol.
Performance can provide information about coordination, attention, ability to follow instructions, balance, and time perception.
But the same concerns present in ordinary SFST review remain important:
- Were instructions complete?
- Was the demonstration correct?
- Were standardized clues accurately identified?
- Were physical limitations considered?
- Were conditions appropriate?
- Does video support the report?
Toxicology Is an Important Comparison
One of the most important components of a drug DUI case is the relationship between the DRE opinion and the subsequent toxicology.
Suppose a DRE concludes that a person is under the influence of a stimulant.
The laboratory result can then be compared with that opinion.
But toxicology also requires interpretation.
Detecting a drug does not automatically prove impairment.
Some drugs or metabolites may remain detectable beyond the period of meaningful impairing effects.
Some concentrations have stronger interpretive value than others.
The timing of specimen collection matters.
The DRE evaluation and toxicology should therefore be evaluated together, not as two automatic boxes that either "match" or "do not match."
DRE Does Not Mean Infallible
DRE training is specialized.
That does not mean every DRE evaluation is automatically correct.
Like any standardized investigative process, its evidentiary value depends on:
- Proper administration
- Accurate observation
- Correct documentation
- Appropriate interpretation
- Consideration of medical explanations
- Correct application of expected drug-category signs
- Consistency with toxicology
- Consistency with video
- Consistency with the person's actual driving and behavior
A comprehensive review should determine whether the conclusion follows logically from the observations.
What Should a DRE Report Be Compared Against?
A DRE report should not be read in isolation.
Useful comparison evidence can include:
- Body-worn camera
- Dash-camera video
- Jail or booking video
- Reports from the arresting officer
- Medical records when relevant
- Blood toxicology
- Statements
- Dispatch and timeline information
- Driving evidence
- SFST video
- Photographs
- Other witness observations
Video can be particularly valuable because it allows reported behavior to be compared with the person's actual presentation.
Three Questions, Not a Checkbox
A Drug Recognition Expert evaluation is much more than a collection of field sobriety tests.
It is intended to be a structured process for answering three broad questions:
Is the person impaired?
If so, is the impairment consistent with drugs rather than, or in addition to, alcohol?
And what drug category or categories are consistent with the observed signs and symptoms?
Those are significant conclusions.
They should be supported by the underlying evidence.
At Legal Limit Consulting, DRE cases can be reviewed step by step, comparing the officer's observations and conclusions with standardized procedures, video evidence, toxicology, expected drug-category effects, and the complete investigative timeline.
Because the words "DRE evaluation completed" are not the end of the analysis.
They are the beginning.
Related reading: THC Blood Tests, Prescription Medication DUI, and Can You Get a DUI With a 0.00 Breath Test?
This article provides general educational information, not legal advice or an opinion about any specific case. Standards, procedures, and evidentiary rules vary by jurisdiction.
If you are an attorney or individual seeking DUI case review, contact Legal Limit Consulting to discuss the case.