By Victoria Cavaliere
WHITE PLAINS, New York (Reuters) - A drug expert testified Thursday that Kerry Kennedy, daughter of assassinated Senator Robert F. Kennedy, might have had an episode of "sleep driving" when she sideswiped a truck on a New York highway in 2012 before passing out behind the wheel.
Kennedy, who has pleaded not guilty to one count of driving while impaired, has argued she accidentally took a sleeping pill instead of a daily thyroid medication the day of the accident.
David Benjamin, a clinical pharmacologist, took the stand in Westchester County Court on Thursday to testify on behalf of the defense. He said Kennedy, 54, might have continued to go through the motions of operating her silver Lexus as the sleep aid zolpidem, known by its brand name Ambien, quickly took effect.
A toxicology report taken after the incident showed Kennedy had zolpidem in her bloodstream.
"I call it a dissociative reaction," Benjamin said of sleep driving. "Essentially they are separated from themselves. ... They are acting on an automatic type of behavior, something they have done many times."
Prosecutors in Westchester County, north of New York City, maintain that even if Kennedy took the sleeping pill accidentally she was liable for her actions and should have stopped driving after realizing she was impaired.
Closing arguments are expected to begin later on Thursday.
A jury trial for impaired driving, a misdemeanor, is unusual but Kennedy, who is also the ex-wife of New York Governor Andrew Cuomo and the niece of assassinated President John F. Kennedy has maintained that she accidentally ingested the pill and did not realize her mistake the morning of July 13, 2012.
Kennedy drove erratically for 5 miles on an interstate highway, tailgating, swerving into other lanes and then crashing into a tractor trailer and driving away, police said. She was found slumped over the wheel of her still-running car.
She testified Wednesday that she had almost no memory of the incident and only hours later realized she might have mixed up her medications.
Westchester County Assistant District Attorney Doreen Lloyd questioned Benjamin on Thursday about whether someone who regularly takes Ambien would recognize its symptoms.
"Someone who regularly takes this drug ... five times a month over the course of 10 years, wouldn't they become aware of how it makes them feel?" Lloyd asked.
Benjamin, a professor at Tufts University School of Medicine outside Boston, said that most users would recognize the effects.
Impaired driving carries up to a one year jail sentence but with no prior record Kennedy, an author and human rights advocate, is unlikely to serve any time.
The driver of the truck Kennedy hit, Rocco Scuiletti, also drove away and had pleaded not guilty to leaving the scene of an accident.
(Editing by Scott Malone; Editing by Richard Chang)