In Commonwealth v. Taylor, the preclusion by the trial court of the defendant’s expert testimony concerning the reliability of sobriety tests to detect drug impairment caused the Superior Court to reverse convictions for driving under the influence and endangering the welfare of a child.

The Defendant was involved in a one car accident. Upon arrival on the scene, the investigating police officer noticed she had bloodshot eyes, slurred speech and appeared confused and very tired. She was asked to perform two standard field tests. She started the tests before being asked to do so and displayed unsteady balance.

She was placed under arrest. She admitted to investigating officers that she had used Adderall and Xanax. No blood test was taken.

At trial, the Commonwealth relied on the testimony of the arresting officer in order to establish that Defendant was driving under the influence. He testified that the defendant’s poor performance on her field sobriety tests was due to drug use.

The defense attributed Ms. Taylor’s poor performance to a possible head injury from the
accident and offered the testimony of their own medical toxicologist/physician. It was his
testimony that there was no scientific basis on which to rely on field sobriety tests to detect drug impairment since those tests have only been validated to establish intoxication from alcohol. The trial court declined to certify the witness as an expert in the methodology behind standard field sobriety tests. The ruling was based on the expert having no experience administering the tests.

The Superior Court found this to be error. The trial record established that the expert had
the knowledge, intelligence and experience to determine whether sobriety tests had been
scientifically validated to detect drug impairment even though he had not personally administered the tests himself.

The Court went on to find the error was so prejudicial that the verdict and sentence had to be vacated. The question before the jury was the cause of Defendant’s impairment- the accident or drug use. The excluded testimony prevented the jury from considering any explanation offered for Defendant’s impairment other than the opinion of the arresting officer. As a result, Defendant was granted a new trial.