Kerry Kennedy's accident a couple of weeks ago, and the role that sleep aids played, highlight the dangers of these kinds of drugs.

Kerry Kennedy was involved in an automobile crash on July 11. Daughter of Robert F. Kennedy and the ex-wife of former New York state governor Andrew Cuomo, Kennedy was driving a car that swerved across Interstate 684 and hit a tractor-trailer.

At the scene, she tested negative for alcohol. Kennedy theorized with police officers that she may have accidentally taken an Ambien pill instead of her thyroid medication. In the North Castle Justice Court, however, she claimed that her doctors had said that the accident had occurred because of a seizure, though she acknowledged her earlier conversation with police officers.

At the scene, she failed sobriety tests and was swaying and slurring her speech, according to officers.

Kennedy pleaded not guilty to driving while drug-impaired.

Blood tests taken after Kennedy's arrest indicate the presence of zolpidem, a chemical found in popular sleep aid Ambien, conflicting with her theory in the courtroom. There were 14 nanograms per milliliter, a very low amount. It would be consistent with someone who had taken a pill right before, or a few hours earlier.

This would contradict her own doctors' findings, but indeed would be consistent with her earlier account. "It now appears my first instinct was correct," Kennedy said in a statement to The Associated Press on Wednesday.

Popular sleep aid Ambien has been implicated in an increased risk for traffic accidents, along with other hypnotic drugs. It also has led to instances of sleepwalking and talking.

According to Ambien's page on manufacturer Sanofi-Aventis website, it warns, "Due to the rapid onset of action, Ambien CR should only be taken immediately prior to going to bed. Patients should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination such as operating machinery or driving a motor vehicle after ingesting the drug, including potential impairment of the performance of such activities that may occur the day following ingestion of Ambien CR."