Discuss as:

Kerry Kennedy says car accident caused by seizure

Kerry Kennedy, a daughter of the late Robert Kennedy, says she believes her recent accident on a New York interstate was caused not by drugs but by a seizure. NBC's Craig Melvin reports.

NEW YORK -- Kerry Kennedy, the ex-wife of New York Governor Andrew Cuomo and daughter of Robert F. Kennedy, pleaded not guilty on Tuesday to a charge of driving while impaired by drugs and said her accident was caused by a "complex partial seizure."

Kerry Kennedy, 52, was found slumped behind the wheel of a white Lexus of Friday morning in the Westchester County town of North Castle an hour's drive north of New York City. A witness said she had hit a tractor trailer and left the scene.

According to a police report she was swaying, had trouble speaking, and told a police officer she may have accidentally taken a sleeping pill on the morning of her accident.

Speaking after her arraignment in local court, Kennedy said she was "confused and erratic" when she spoke to police and denied that her accident was caused by drugs.

Investigators say Kerry Kennedy admitted she had taken an Ambien after being arrested for driving while under the influence on Friday, but family members are now suggesting the mother of three may have suffered a seizure. NBC's Jonathan Dienst reports.

Watch the Top Videos on NBCNews.com

"I have never had any history of drug or alcohol abuse," Kennedy, who is known for her work in human rights, told reporters outside the North Castle Court. She was flanked by members of her family and her lawyer.

Kennedy said she did not remember anything after entering a southbound highway from her home to go to the gym and before finding herself stopped at a traffic light with a police officer at her car door.

Craig Ruttle / AP

Kerry Kennedy flanked by her brother Christopher Kennedy, second left, and sister Rory Kennedy, right, walks from the North Castle Justice Court in Armonk, N.Y. on Tuesday, July 17, 2012.

Tests at a local hospital soon after the incident showed no alcohol or prescription drugs in her system, she said, and further neurological tests led her doctor to believe she had suffered a seizure for the first time in her life.

"This accident was not caused by a sleeping aid, but a complex partial seizure," Kennedy said. Kennedy said she would continue to receive treatment for the condition and should be able to live "symptom-free."

Results of urine and blood tests are still pending, a police report said. These would be subject of her next court appearance on August 14, her lawyer Robert Gottlieb said.

She apologized to the driver of the tractor-trailer she hit and other drivers on the road Friday morning

Kennedy's accident came two months after her sister-in-law and close friend, Mary Kennedy, killed herself. Mary Kennedy was the estranged wife of Robert F. Kennedy Jr., the son of the late Senator Robert F. Kennedy and nephew of the late President John F. Kennedy.

Reuters and The Associated Press contributed to this report.