The charge stems from a 2012 highway collision outside New York City that Kennedy blames on her accidentally taking a sleeping pill.
Her lawyer said after a court session Thursday that he asked the judge to reconsider a previous judge's refusal to dismiss. He says the prosecution recently acknowledged it has no evidence Kennedy took the pill on purpose.
A district attorney's spokesman declined to comment.
The judge announced that if the case is not dismissed, the trial will begin Feb. 24. Kennedy waived her right to attend jury selection.
She said afterward she would be on a trip campaigning against child slavery on behalf of a human rights organization named for her late father, Sen. Robert Kennedy.