The girl was charged at age 10 with juvenile manslaughter over the summer in the death of 3-month-old Brooklyn Foss-Greenaway, who was staying overnight in the girl's home in Fairfield in the care of the girl's mother.
The girl, now 11, entered a plea of "no answer" in District Court in Skowhegan. Her only other choices were "guilty" and "not guilty." Maine District Court Judge Charles LaVerdiere ordered a competency hearing for her.
The girl's mother called police early on July 8 to report that the infant was not breathing, authorities said. The infant, who was reportedly fussy, was sleeping in a portable crib in the 10-year-old's bedroom that night, said the infant's mother, Nicole "Nicki" Greenaway of Clinton.
The state hasn't released the cause of death, but Greenaway was told that her daughter ingested medication and was suffocated.
"They both need to go to jail," Greenaway told WZON radio before the hearing got under way Monday. "The need to wake up every morning and look at those bars and realize what they did."
The Maine Department of Health and Human Services, which removed the young suspect from the home, faulted the baby sitter for leaving the infant in the room with the girl. In a letter, an agency case worker said the 10-year-old had a behavior disorder that made her unsuitable for caring for the infant.
The Associated Press generally does not identify juveniles accused of crimes.
The state opted not to try the girl as an adult. If convicted as a juvenile, the maximum penalty is incarceration until age 21.
LaVerdiere issued a special order warning that no recording device of any type was allowed in the courtroom Monday.
