SC Implied Consent & the Drug Recognition Expert (DRE) Protocol

Last verified: May 2026

The Implied-Consent Statute

South Carolina’s implied-consent law — codified at S.C. Code § 56-5-2950 and a series of related sections — provides that any person who drives a motor vehicle in this state has, by the act of driving, consented to a chemical test of blood, breath, or urine for the purpose of determining the presence of alcohol or drugs, if arrested on probable cause for DUI under § 56-5-2930. The arresting officer must inform the driver of the consequences of refusal, including the administrative license suspension. The implied-consent statute is structurally separate from the DUI statute itself: a driver may decline the chemical test, but doing so triggers automatic adverse administrative consequences regardless of whether the underlying DUI prosecution succeeds. See no per se limit page.

Refusal Consequences

• First refusal: 6-month administrative driver’s license suspension by the SC Department of Motor Vehicles, separate from any criminal-court outcome.
• Second refusal within 10 years: 9-month suspension.
• Third refusal within 10 years: 12-month suspension.
• Fourth or subsequent: 15-month suspension.
• The refusal itself can be introduced into evidence at trial as consciousness of guilt — an element of "implied consent" jurisprudence is that the prosecution may argue the refusal evidences awareness of impairment.
• Eligibility for the Ignition Interlock Device program may be triggered or required as a condition of license reinstatement following implied-consent suspensions on alcohol-DUI dispositions.

The Strategic Tradeoff

Defense counsel routinely advise drivers facing a suspected cannabis DUI on the tradeoff embedded in implied-consent decision-making at the roadside. Submitting to the chemical test produces a numeric toxicology result — useful to the state if the THC concentration is high, useful to the defense if it is low, particularly in a state with no per se threshold. Refusing the test deprives the state of the toxicology evidence but triggers the automatic license suspension and creates the adverse-inference argument at trial. The right choice in any given case depends on the strength of the officer’s impairment observations, the driver’s recent cannabis use, and the specific facts of the stop. The decision must be made at the roadside, often without counsel, in a high-stress environment.

The Drug Recognition Expert (DRE) Protocol

The DRE program is a national curriculum administered by the International Association of Chiefs of Police (IACP) in coordination with the National Highway Traffic Safety Administration (NHTSA). South Carolina has trained DRE officers across SLED and major county and municipal departments. A DRE evaluation is ordinarily conducted at the booking facility after arrest, in a controlled environment with the driver removed from the roadside. The standard 12-step protocol includes:

1. Breath alcohol test — to rule out alcohol as the principal cause of impairment.
2. Interview of the arresting officer — to gather context about driving behavior and roadside observations.
3. Preliminary examination and first pulse — visual examination of the subject, vital signs.
4. Eye examination — Horizontal Gaze Nystagmus (HGN), Vertical Gaze Nystagmus (VGN), Lack of Convergence (LOC).
5. Divided-attention psychophysical tests — Romberg balance, Walk-and-Turn, One-Leg Stand, Finger-to-Nose.
6. Vital signs and second pulse — blood pressure, body temperature, second pulse reading.
7. Dark-room examinations — pupil-size measurements under three lighting conditions; examination of the oral and nasal cavities.
8. Examination for muscle tone — flaccid, normal, or rigid.
9. Check for injection sites and third pulse.
10. Subject’s statements and other observations — Miranda-warned interview.
11. Analysis and opinion of the evaluator — the DRE’s formal conclusion as to drug category (typically: cannabis, central nervous system depressants, CNS stimulants, hallucinogens, dissociative anesthetics, narcotic analgesics, inhalants).
12. Toxicological examination — blood or urine specimen for laboratory analysis.

The Cannabis Indicators in DRE Practice

Per IACP/NHTSA training materials, the cannabis indicator profile in a DRE evaluation typically includes: dilated pupils, elevated pulse, elevated blood pressure, lack of convergence (eyes failing to cross when tracking a stimulus toward the nose), eyelid tremors, body tremors, divided-attention test deficits (Romberg sway, Walk-and-Turn errors), reddened conjunctiva, dry mouth, and slow speech. Note that several of these indicators — elevated pulse, elevated blood pressure, divided-attention deficits — are nonspecific and can be produced by stress, anxiety, fatigue, or underlying medical conditions; the defense bar focuses heavily on the nonspecificity of the cannabis indicator set in cross-examination.

Defense Challenges to DRE Validity

South Carolina defense counsel routinely challenge DRE evidence on several grounds:

• Foundational scientific validity. DRE protocol’s validation studies have been criticized in peer-reviewed literature for design weaknesses (small samples, lack of double-blinding, ground-truth confounds). The protocol was not developed in the same controlled manner as ordinary forensic disciplines. Defense experts argue the cumulative cannabis-detection accuracy is not sufficient to support a beyond-reasonable-doubt conviction without strong corroborating evidence.
• Officer training and certification. The defense will examine the specific DRE’s certification status, recency of training, evaluation logs, and prior testimony to identify inconsistencies.
• Specificity of indicators. Many cannabis indicators are nonspecific. Cross-examination focuses on whether each indicator could be explained by a non-cannabis cause (medical condition, prescription medication, stress).
• Toxicology reconciliation. If the toxicology screen produces a low or borderline THC concentration, defense counsel argue that the DRE conclusion is inconsistent with the laboratory result.
• SFST limitations. SFSTs were validated principally for alcohol; cannabis impairment manifests differently, and SFST performance may be a poor proxy.

The State’s Response

Solicitors’ offices in South Carolina respond that DRE evidence is corroborative, not dispositive: the prosecution’s case is built from the totality of officer observations, SFST results, DRE evaluation, and toxicology together, rather than relying on any one element. The 2020 admissibility status of DRE testimony in South Carolina is governed by ordinary expert-witness rules under SCRE 702; the foundational reliability inquiry is for the trial court. Defense Daubert-style challenges have produced mixed outcomes; many trial courts admit DRE testimony with cross-examination as the primary defense response. See opposition coalition page.

Toxicology Reconciliation

South Carolina’s blood-test process for suspected cannabis DUI typically proceeds as follows: after arrest, the driver is transported to a medical facility (in many counties, the Spartanburg Regional, Prisma, MUSC, or Roper-affiliated emergency department) where a phlebotomist draws a sample under chain-of-custody protocol; the sample is sealed and transported to SLED’s forensic toxicology laboratory or a contract laboratory. Testing typically includes immunoassay screening followed by gas-chromatography mass-spectrometry confirmation for THC and the THC-COOH metabolite. The reported result is a numeric concentration; without a per se threshold, the number is corroborative of the impairment evidence rather than dispositive.

Practical Implications

• Implied-consent refusal triggers automatic license suspension independent of criminal-court outcome.
• The decision to submit or refuse the chemical test is high-stakes and case-dependent. Drivers should not refuse without understanding the administrative consequences.
• DRE evidence is admissible in SC, subject to ordinary expert-witness foundation rules. Defense challenges focus on training, indicator specificity, and toxicology reconciliation.
• Toxicology numbers in SC are corroborative, not dispositive — both prosecution and defense argue them in light of the impairment evidence.
• Federal-employer drug-testing rules are entirely separate from the implied-consent and DRE framework. A positive THC test triggers federal adverse action regardless of state DUI outcome. See federal installations.
• Defense counsel should be retained early. The implied-consent administrative-suspension hearing is a separate proceeding before the SC Office of Motor Vehicle Hearings (OMVH); it has its own deadlines and procedural rules.