Judge Charles LaVerdiere of Skowhegan District Court, Maine, ruled Monday to close the hearing despite an objection from the state, the Bangor (Maine) Daily News reported.
The unnamed girl is charged with reckless or criminally negligent manslaughter in the death of Brooklyn Foss-Greenaway, who died in July while the 11-year-old was babysitting.
The baby's mother, Nicole Greenaway of Waterville, Maine, said in August a toxicology report on the infant revealed medication for attention deficit disorder was found in the baby's system, the same medication prescribed to the 11-year-old.
The autopsy report hasn't been made public, the newspaper said.
Celebrity Families of 2014 [PHOTOS]