Cops busted her for driving under the influence of a prescription drug, after she crashed into a truck, fled the scene and then fell asleep at the wheel.
Police say Kennedy was driving erratically on Interstate 684 before she hit the tractor trailer.
They also say she had taken Ambien , the powerful sleeping pill.
The 52-year-old Kennedy will appear in court next week to face charges for the accident.
A spokesman for Kennedy says she was in fact not impaired.
The incident took place in the town of North Castle in Westchester County.
According to state police, authorities received 911 calls that a white Lexus SUV heading southbound had collided with a tractor trailer, sustaining damage and a flat tire.
The Lexus pulled off along route 22, which is where sources tell ABC News, police found Kerry Kennedy asleep at the wheel.
Sources say Kennedy was cooperative and told investigators she had taken a prescription sleeping pill, likely Ambien.
But that's something Ken Sunshine, a Kennedy spokesman denied in a written statement: "Kerry Kennedy voluntarily took breathalyzer, blood and urine tests - all of which showed no drugs or alcohol whatsoever in her system. The charges were filed before the test results were available."
Eyewitness News went to the Mount Kisco home of Kennedy, a mother of three girls but were told no one would speak to us about the incident.
"On the heel of what happened with the death, it just really seems a little bit kind of strange even that there's always something going on," said Vicky Bezzetto.
Bezzetto, a teacher in the town, is referring to the recent suicide of Mary Kennedy who had been married to Kerry Kennedy's brother, RFK Jr.
Kerry Kennedy has been mourning Mary's death.
Kennedy is a lawyer, writer and human rights activist.
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