(CNN) -- Kerry Kennedy, daughter of the late Sen. Robert F. Kennedy and ex-wife of New York Gov. Andrew Cuomo, could take the witness stand Wednesday morning to testify in her own defense in her DWI trial stemming from a 2012 traffic accident.
Kennedy is facing a misdemeanor charge of driving while intoxicated for allegedly swerving between lanes and careening into a tractor-trailer on a Westchester County, New York, interstate in July of 2012. She drove away from the accident scene despite a shredded tire, and was found collapsed over the steering wheel of her Lexus SUV a short time later, according to testimony.
Kennedy has said she swallowed a pill she believed to be her thyroid medication at around 7:30 the morning of the incident, but that she may have mixed up medicine bottles and taken zolpidem, a powerful sleep aid, instead. A blood test confirmed the presence of zolpidem in Kennedy's system, according to trial testimony this week.
At the start of her defense case Tuesday, Kennedy watched with a smile as her younger sister Rory Kennedy described their close relationship. "She's really my best friend," said the younger Kennedy on the stand.
When asked about her sister's reputation for truthfulness, she said, "She wrote the book called 'Speak Truth to Power' about her commitment to justice and truth, and that's what she has devoted her life to."
A growing group of supporters have sat in the rows behind the defendant throughout the two trial days in Westchester County, including sister Kathleen Kennedy Townsend, brothers Robert F. Kennedy Jr. and Douglas Kennedy, and 85-year-old family matriarch Ethel Kennedy.
Earlier Tuesday, jurors heard from Bradley Molloy, a drug-detection specialist with the New York State Police who evaluated Kennedy after the crash. Some three hours after she allegedly failed three roadside sobriety tests, Kennedy passed those same tests with flying colors, testified Molloy.
Finding no signs of intoxication, Molloy instead began to suspect that Kennedy's car accident and disoriented state had been the result of a medical condition, he said.
Kennedy herself was also worried, and asked that a vial of the blood drawn from her at Northern Westchester Hospital, said Molloy: "She was concerned and she wanted to know what happened to her." Kennedy remained at the hospital overnight for observation.
During opening statements Monday, Assistant District Attorney Stefanie DeNise said that even if Kennedy, 54, had taken the sleep aid unintentionally, she had a responsibility to pull her vehicle off the road safely when she began to feel its effects.
Defense attorney Gerald Lefcourt disputed that argument, saying Kennedy had no time to react. "The zolpidem kicks in, it shuts her down, she's in a state of 'sleep driving,'" he said.
Tuesday afternoon, jurors watched another member of Kennedy's defense team spar with an expert witness about the effects of the drug.
Laboratory director Elizabeth Pratt conceded that zolpidem is "a very potent, fast-acting hypnotic," that begins to hamper cognitive ability and motor skills within 15-45 minutes. Its effect on Kerry Kennedy would have peaked at around 9 a.m., testified Pratt; roughly the time Kennedy failed an initial round of sobriety tests by police after a motorist called 911.
Pratt was asked by prosecutor Doreen Lloyd whether zolpidem is a "knock-out pill," and replied that the drug would need time to enter the blood stream and brain before it takes full effect.
"And, prior to the time the drug takes effect, does a person still have brain function? Do they still have decision-making ability?" asked Lloyd. "Yes," replied Pratt.
The trial continues Wednesday at 9:30 a.m.