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.