In a legal battle focused on an expert witness, a sharply divided Florida Supreme Court allowed a medical-malpractice case to move forward in the death of a 20-year-old woman after she had given birth to a stillborn child.

The justices, in a 4-3 decision, overturned rulings by a circuit judge and the First District Court of Appeal that the case should be dismissed. The decision also underscored long-running legal and political disputes about requirements for expert witnesses, who can play a pivotal role in medical-malpractice cases.