Citing cases dating back as far as 1928, a judge has ruled that a young girl accused of running down an elderly woman while racing a bicycle with training wheels on a Manhattan sidewalk two years ago can be sued for negligence.

The ruling by the judge, Justice Paul Wooten of State Supreme Court in Manhattan, did not find that the girl was liable, but merely permitted a lawsuit brought against her, another boy and their parents to move forward.

The suit that Justice Wooten allowed to proceed claims that in April 2009, Juliet Breitman and Jacob Kohn, who were both 4, were racing their bicycles, under the supervision of their mothers, Dana Breitman and Rachel Kohn, on the sidewalk of a building on East 52nd Street. At some point in the race, they struck an 87-year-old woman named Claire Menagh, who was walking in front of the building and, according to the complaint, was “seriously and severely injured,” suffering a hip fracture that required surgery. She died three months later of unrelated causes.

Her estate sued the children and their mothers, claiming they had acted negligently during the accident. In a response, Juliet’s lawyer, James P. Tyrie, argued that the girl was not “engaged in an adult activity” at the time of the accident — “She was riding her bicycle with training wheels under the supervision of her mother” — and was too young to be held liable for negligence.

In legal papers, Mr. Tyrie added, “Courts have held that an infant under the age of 4 is conclusively presumed to be incapable of negligence.” (Rachel and Jacob Kohn did not seek to dismiss the case against them.)

But Justice Wooten declined to stretch that rule to children over 4. On Oct. 1, he rejected a motion to dismiss the case because of Juliet’s age, noting that she was three months shy of turning 5 when Ms. Menagh was struck, and thus old enough to be sued.

Mr. Tyrie “correctly notes that infants under the age of 4 are conclusively presumed incapable of negligence,” Justice Wooten wrote in his decision, referring to the 1928 case. “Juliet Breitman, however, was over the age of 4 at the time of the subject incident. For infants above the age of 4, there is no bright-line rule.”