( 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 . '' Trial opens with video of sobriety tests , claim of 'sleep driving ' 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 .
Kerry Kennedy , daughter of the late Sen. Robert F. Kennedy , was in an accident in 2012 . She suffered a broken leg and arm but is expected to make a full recovery. She is on trial on a misdemeanor charge of driving while intoxicated . Kennedy says she took what she thought was medicine but it could have been a sleep aid .