ARMONK, N.Y. >>  Kerry Kennedy, ex-wife of New York Gov. Andrew Cuomo, was swaying and slurring her speech when police found her after her car hit a tractor-trailer on a highway, police said in a court document.

Kennedy, daughter of Sen. Robert Kennedy and niece of President John Kennedy, also told police she might have accidentally taken a sleeping pill before the Friday morning accident.

The document, a police officer’s deposition, was released several hours before Kennedy was to appear Tuesday night for arraignment on a charge of driving while drug-impaired. Her lawyer said she would plead not guilty.

Kennedy, 52, failed a standing-on-one-leg test and a walk-and-turn test, was swaying and demonstrated impaired speech and motor function, the officer wrote. She was able to recite the alphabet, the document indicates.

Kennedy was arrested Friday after state police said her Lexus struck a tractor-trailer on Interstate 684 north of New York City. Police said she drove the damaged car off the highway before it became disabled.

A witness reported that Kennedy “appeared to be slumped over the wheel,” according to the deposition.

The officer, identified as Officer J. Thomas, wrote that Kennedy told him “she had a thyroid medication and a sleeping medication (believed to be Ambien) and it is possible she took the sleeping pill instead of the thyroid pill.”

It has been a difficult year for Kennedy family members in the New York suburbs. Kennedy’s close friend and sister-in-law, Mary Kennedy, hanged herself at home in May. Her brother Douglas Kennedy is fighting charges stemming from his attempt to take his newborn son from a maternity ward.

Kerry Kennedy and Andrew Cuomo married in 1990, joining two of America’s most prominent political families. They split in 2003 in a messy public divorce that played out in the tabloids. They have three daughters.