Rule 702 Expert Testimony

November 5, 2025

Auto-Brewery Syndrome DWI North Carolina

The Limits of Chemical Certainty: The Auto-Brewery Syndrome & DWI Charges

Auto-Brewery Syndrome (ABS) remains a bit of a theoretical curiosity. It represents a measurable biochemical anomaly during which yeast or bacteria residing in the gastrointestinal tract convert carbohydrates into ethanol within the human body.

Though somewhat rare, it is medically documented, scientifically verifiable in some instances, and possibly legally consequential, at least relative to DUI charges in North Carolina.

July 12, 2025

Eyelid Tremor Cannabis DRE: Unreliable Under Rule 702

by Carolina Attorneys

Should Eyelid Tremor Be Used to Prove Cannabis Impairment in North Carolina?

For years, the Drug Recognition Evaluator (DRE) protocol has relied on a structured set of physical observations to evaluate suspected drug impairment. Among these, the presence of eyelid tremor has been taught as a supposed sign of recent cannabis use. In practice, that means law enforcement officers conducting roadside evaluations or testifying in court may point to an eyelid tremor as evidence supporting probable cause or impairment. But as a recent study published in Clinical Toxicology makes clear, the scientific foundation for this assumption is, at best, unproven. At worst, it is affirmatively misleading.

In a 2024 peer-reviewed clinical research article by George Sam Wang and colleagues, the authors conducted a carefully controlled, blinded study to evaluate whether eyelid tremor could reliably and accurately be identified as a marker of recent cannabis use. The conclusion was clear. Eyelid tremor does not correlate with cannabis ingestion in a scientifically defensible way. Inter-rater reliability was poor to moderate. Specificity was dismal. And perhaps most importantly for DWI defense lawyers, the entire protocol used by officers to “spot” this supposed indicator would not come close to passing scientific muster in any peer-reviewed laboratory setting.

March 22, 2025

Marijuana Identification in North Carolina: State v. Ruffin and Rule 702 Expert Testimony

by Carolina Attorneys

The North Carolina Court of Appeals’ recent decision in State v. Ruffin, ___ N.C. App. ___ (Mar. 5, 2025), provides guidance on marijuana identification in the post-hemp era. The defendant in Ruffin was convicted of multiple drug offenses, including the sale and delivery of marijuana, arising from a controlled buy in 2021.

On appeal, the accused challenged the identification of the seized plant material as marijuana (arguing it could have been legal hemp), the admissibility of both lay and expert testimony under the North Carolina Rules of Evidence, the sufficiency of the evidence to distinguish marijuana from hemp, the trial court’s jury instructions, and several aspects of his sentencing

The Court of Appeals affirmed the convictions and sentences. This article analyzes Ruffin and its implications for North Carolina law, with specific reference to Rule 702 Testimony by Expert Witnesses.