New York ( CNN ) -- Kerry Kennedy , the daughter of the late Robert F. Kennedy and ex-wife of New York Gov . Andrew Cuomo , said a partial seizure is the cause of a Friday morning car crash . At a press conference on Tuesday , Kennedy also said the seizure might have been from a previous injury she suffered on the right side of her brain . Kennedy , 52 , was found by state police behind the wheel of her damaged Lexus SUV . A New York State Police press release said the SUV collided with a tractor-trailer . Kennedy charged in hit-and-run . At a hearing on Tuesday in district court in North Castle , New York , Kennedy pleaded not guilty to charges of driving while impaired . The judge released her under her own recognizance . At the press conference after the hearing , Kennedy said she told the officer who arrived at the scene : `` It is theoretically possible that I might have taken an Ambien rather than a thyroid pill '' earlier that morning . Kennedy said she remembers nothing of her alleged erratic driving , from getting on the highway until the officer stopped her at a traffic light . `` A subsequent investigation found Kennedy to be operating the motor vehicle while her ability was impaired by drugs , '' police said in announcing the charge against her on Friday . At Tuesday 's press conference , Kennedy said she went to Northern Westchester Hospital , where she was tested for recreational drugs , prescription drugs and alcohol . Kennedy said the results came up negative . Commerce secretary resigns after seizure , two auto accidents . She did not say whether her thyroid medication showed up in the test results . Determined to understand her medical condition , Kennedy said she visited Mount Sinai Medical Center , where she underwent `` a full battery of neurological testing . '' `` Doctors believe that the crash was caused not by a sleeping aid , but by a complex partial seizure , '' Kennedy said . She did not take questions . This is the second time this year that a high-profile person suffered a seizure that resulted in a car accident . In June , U.S. Commerce Secretary John Bryson , who has since resigned , was involved in two car crashes in the Los Angeles area before being found unconscious in his car , police said . Bryson was not charged . Seizures : When 'electrical brainstorm ' hits .
Police say Kennedy hit a tractor - trailer on Friday night . She says doctors said she had a ` ` complex partial seizure '' Kennedy pleaded not guilty to charge of driving while impaired .