Polysubstance DUI Defense in Georgia

Polysubstance DUI prosecutions are presented to juries as the strongest version of the State's case: not one substance, but two; not one category of impairment, but several. On careful examination, the opposite is frequently true. The science becomes less precise, the pharmacology less predictable, and the State's witnesses less able to say what a chemistry report actually establishes about driving.

I · The StatuteLess-safe, by any combination

O.C.G.A. § 40-6-391(a)(4) permits the State to charge impairment by the combined influence of alcohol and one or more drugs. The element the State must prove is the same as in any less-safe prosecution: impairment to the extent that it is less safe for the person to drive. The combination theory does not lower that burden. It increases the explanatory work the State has to do.

II · The Pharmacology GapInteractions are real and individualized

Pharmacologic interactions between commonly co-occurring substances — alcohol and benzodiazepines, cannabis and prescription opioids, stimulants and antidepressants — are well documented in the medical literature. They are also dose-dependent, tolerance-dependent, metabolism-dependent, and time-course-dependent. A toxicologist can describe an interaction profile in the abstract. A toxicologist cannot, absent specific clinical observation, quantify the contribution of each substance to a particular driver's behavior on a particular night.

The cross-examination work is to separate, on the record, what is general pharmacology from what is case-specific science. The witness almost always concedes the distinction once it is put plainly.

III · The DRE ProtocolTwelve steps, and what each step actually establishes

Drug Recognition Evaluations are central to polysubstance prosecutions because the chemistry, standing alone, rarely tells the State's story. The twelve-step protocol — breath alcohol, interview of the arresting officer, preliminary examination, eye examination, divided-attention tests, vital signs, dark-room examination, muscle tone, injection-site examination, subject statements, opinion, toxicology — is presented as if it were a clinical assessment. It is not. It was developed by law enforcement, validated against laboratory toxicology rather than driving performance, and its predictive value for impairment on the road has never been established to the standard a peer-reviewed scientific instrument would require.

That does not make DRE testimony inadmissible. It does make it susceptible to careful examination on:

1. Whether each step was performed in accordance with the protocol;
2. Whether the conditions of administration matched the validation environment;
3. Whether the documented vital signs are consistent with the categories opined;
4. Whether the eye examination findings are documented or merely conclusory;
5. Whether the toxicology actually corroborates the opinion — and where it does not.

IV · Prescription MedicationLawful use is part of the record

Many polysubstance prosecutions involve prescribed benzodiazepines, prescribed opioids, prescribed stimulants, or prescribed antidepressants. The defense almost always begins with whether the medication was being taken as directed, what the prescribing physician knew about driving, what the patient's tolerance and history actually were, and whether the toxicology values are consistent with therapeutic, supratherapeutic, or otherwise interpretable levels. None of that information appears on the State's certificate. All of it appears in records the defense develops and presents.

V · The Trial PostureDiscipline, not denial

Polysubstance trials are not won by denying that the defendant consumed anything. They are won by isolating, in plain language, the distance between what the State has proven (consumption, concentration, observation) and what the State has charged (impairment to the less-safe standard, at the moment of driving). A Georgia jury that follows that distance to the end of the case frequently does what the law asks it to do.

The State's strongest cases on paper are sometimes the cases in which the chemistry, candidly examined, does the least work for the prosecution.

VI · Related Reading

• Defending Marijuana DUI Allegations in Georgia
• The Limits of SFSTs in a Drug DUI Prosecution
• THC Blood Testing in Georgia: GBI Methodology
• Georgia DUI-Drugs Defense — Practice Overview

This article is general information and does not constitute legal advice. Prior results do not guarantee a similar outcome.