(CNN) -- Did Kerry Kennedy realize the morning of a 2012 traffic accident that she mistakenly took a sleeping pill? Is she responsible for what happened next?
Those are the sorts of questions the jurors in her DWI trial began deliberating Thursday.
In closing arguments, a prosecutor accused Kennedy of lying to police and the public in an effort to protect her legacy.
Kennedy, daughter of the late Sen. Robert F. Kennedy, faces a charge of driving while impaired after swerving off the road in her Lexus SUV and careening into a tractor-trailer on a New York interstate in morning rush-hour traffic in July 2012.
She testified this week that she grabbed the wrong prescription bottle off her kitchen counter that morning and swallowed 10 milligrams of zolpidem, commonly known by the brand name Ambien, thinking it was her thyroid medication.
"She had a lot on her mind that morning. And she took the wrong pill by mistake," prosecutor Doreen Lloyd told jurors.
"However, it also makes no sense whatsoever that at no point did she realize or feel tired or dizzy or drowsy. That makes no sense," she said. "She is responsible for the chain of events that happened after that."
Lloyd told jurors that Kennedy had a responsibility to pull off the road safely when she felt the effect of the drug. Her inconsistent statements about the incident, including the claim that her doctors said she'd had a seizure, were meant as a smokescreen, Lloyd said: "She knew. She knew right away that she had taken the wrong pill. She felt it. And I submit she was looking for an excuse, to avoid responsibility ... to control her public image."
In his closing arguments, defense attorney Gerald Lefcourt told jurors there's no disputing that Kennedy ingested zolpidem and was "out of it" the morning of the crash.
"The dispute is this: Whether the prosecution has proved to you beyond a reasonable doubt that Ms. Kennedy operated her vehicle while she was aware that she had ingested zolpidem and, after becoming aware, she continued intentionally to drive. That's what this case is all about."
He continued, "They're arguing without any evidence that she realized; she says she didn't. There's nothing to the contrary. Reasonable doubt."
A jury of two women and four men began its deliberations Thursday afternoon, after four days of testimony. They stopped for the day without reaching a verdict and will resume deliberations Friday morning.
This week, jurors watched police cruiser dashboard camera footage of a disoriented Kennedy failing three sobriety tests after a motorist found her slumped over her steering wheel and called 911.
New York State Trooper Bradley Molloy, who evaluated Kennedy three hours after the crash, said he thought she may have a medical condition and recommended that she get checked out. A worried Kennedy asked him for a vial of the blood drawn from her at Northern Westchester Hospital, Molloy said: "She was concerned, and she wanted to know what happened to her." Kennedy remained at the hospital overnight for observation.
Jurors also heard from Elizabeth Pratt, director of the Westchester County Division of Laboratories and Research, who testified that zolpidem is "a very potent, fast-acting hypnotic" that begins to hamper cognitive ability and motor skills within 15 to 45 minutes. Its effect on Kennedy would have peaked about 9 a.m., testified Pratt, roughly the time Kennedy failed the sobriety tests.
Lloyd asked Pratt whether zolpidem is a "knockout pill," and she replied that the drug would need time to enter the bloodstream and brain before it takes full effect.
A defense expert, clinical pharmacologist and forensic toxicologist David Benjamin, challenged that notion Thursday, saying the disabling influence could be instantaneous and impossible for a person to self-detect, likening it to the effects of a date rape drug.
During her testimony, Kennedy emphatically denied feeling the effects of the powerful sleep aid in her system before the erratic driving and told Lloyd she doesn't even know what its symptoms feel like.
"You've taken this pill for 10 years, and you can't tell me whether or not it makes you feel tired after you take it?" Lloyd asked incredulously.
"I guess I don't really think about how I'm feeling when I take it," Kennedy replied. "I take it, and then I'm asleep."
The jury is well-aware of the defendant's place in the storied political family.
"Daddy was the attorney general during the civil rights movement and then a senator," she testified Wednesday, and said her mother raised the family's 11 children because her father died when she was 8 years old: "He was assassinated while running for president."
Matriarch Ethel Kennedy, 85, has attended the trial daily, along with several other relatives and family friends.
Kennedy is the director of the Robert F. Kennedy Center for Justice and Human Rights and became animated on the stand as she described her work to fight poverty and sexual slavery. She testified that she missed jury selection last week because of a trip to several European nations, including a meeting with Secretary of State John Kerry in France and another in Brussels with the president of the European Parliament.
In her closing arguments, Lloyd told jurors that Kennedy's humanitarian work and background are irrelevant: "She is not exempt to the rule of law. She is subject to the rule of law of the state of New York like everybody else."
If convicted, Kennedy could face up to one year in prison.