PA DUI Conviction Reversed Over Improper Impairment Testimony

Posted in DUI on May 24, 2026

In Commonwealth v. Gause, the Pennsylvania Superior Court delivered a significant decision limiting the use of police opinion testimony in DUI–controlled substance prosecutions. The Court vacated the defendant’s conviction and discharged him entirely, finding both evidentiary error and insufficient evidence to sustain the charges.

Factual Background

The case arose from a late-night traffic stop for non-functioning taillights. During the stop:

Gause refused to submit to a blood test, so the Commonwealth did not have forensic evidence to show that his blood contained alcohol or marijuana.  Gause was charged with DUI under 3802(a)(1), which alleged that he had a sufficient amount of alcohol such that he was too drunk to drive safely; and Gause was charged with DUI under 3802(d)(2), which alleged that he was impaired by drugs to the extent that he was incapable of safe driving.

Prior to trial, the defense attorney filed a motion seeking a ruling that the officer should not be permitted to testify that the eyelid and body tremors were indicative of marijuana use as the officer was not an expert in the medical field. The judge denied the defense motion and permitted the testimony to be presented at trial.  After hearing the evidence, the jury convicted Gause of DUI, and Gause then filed an appeal to the Pennsylvania Superior Court.

The Core Legal Issue: Lay Opinion vs. Expert Testimony

Gause’s appellate attorney argued that the officer’s testimony regarding the association of tremors and marijuana use should not have been admitted because it was expert testimony that was being presented by a lay witness. The Superior Court agreed with the defense and stated that the association of eyelid tremors to marijuana use required specialized knowledge and thereby could only have been presented via expert testimony.  The Superior Court further held this was reversible error.

Expert Testimony Not Needed in Every Drug-DUI Case

The Court did NOT upset precedent and hold that expert testimony must be used in every drug-DUI case.  They noted the Griffith decision and advised that whether or not expert testimony is needed must be evaluated on a case-by-case basis, and the primary consideration is whether there is independent evidence of impairment.  In many drug-DUI cases, there is evidence of recent use, such as the odor of marijuana or the presence of paraphernalia. The driver may admit to having recently smoked. In such cases, an expert may not be needed to link the defendant’s behaviors to marijuana use. In the Gause case, so such independent evidence of marijuana use existed, so the court stated that expert testimony was required to present sufficient evidence of impairment to sustain the convictions.

DUI Convictions Vacated

Because the required expert testimony was not presented, the Commonwealth failed to present proof beyond reasonable doubt that Gause was guilty of either DUI offense.  The Court vacated or set aside the convictions and even went the extra step of dismissing the charges so the Commonwealth could not retry Gause. The Commonwealth had gotten its “one bite at the apple” and failed to present sufficient evidence, and the Court would not give them a second chance.

Conclusion

This case highlights the importance of having a great criminal defense attorney. Despite note winning the case at trial, the defense lawyer continued to fight and ultimately prevailed. One of my favorite case victories involved the warrantless entry into my client’s home to arrest him for suspicion of DUI. I sought suppression of evidence in a pretrial motion, but the motion was denied. After the client was convicted, an appeal was taken to the Superior Court. The Superior Court agreed with me that the police needed to obtain a warrant in order to enter my client’s residence, so the court reversed the conviction. After the case was returned to the trial court, the District Attorney dismissed the case. Anyone charged with a criminal offense should hire an experienced criminal defense attorney.  Experience and skill matter.