Bart Lubow, the director of the Juvenile Justice Strategy Group at the Annie E. Casey Foundation, a national child advocacy organization based in Baltimore, said a 5-year-old is incapable of forming intent, and likely wouldn't even know what drowning means.

"You can imagine a child responding to other children's crying by saying, 'I know how to stop that.' But the notion that there was intent there is silly," Lubow said. "For a 5-year-old, this is well beyond the pale of what our criminal or delinquency laws are intended to address."

He said the case should proceed with a "very child-centered approach."

Police said the 5-year-old was not arrested, and the case was referred to the Jackson County's family courts division.

Police originally ruled Friday's death accidental, but said that changed after social workers reported that the girl told them she brought the toddler into the bathroom and drowned him.

"The 5-year-old became upset when the child wouldn't stop crying and took the 2-year-old into the bathroom and drowned him," said Officer Darin Snapp, a spokesman for the Kansas City Police Department. He said the two children were related, but it was unclear exactly how.

"As of right now yes, from her statement, she is a possible suspect," Snapp said.

The children had been left along with others under the supervision of a teenager while an adult in the home went to pick up the father of the 18-month-old, Snapp said. He said the father had recently arrived in Kansas City to take the infant back to their home in St. Louis. It was unclear how long the adult was out of the home.

Mary Jacobi, a spokeswoman for the Jackson County Court, said she could not comment on the girl's current whereabouts.

"We cannot speak at all to the child's current living arrangement," she said.

She said in an email that the Missouri Children's Division had been notified and that a juvenile officer involved in the case had filed a petition for a child in need of care for the 5-year-old. Such a petition would allow the court to determine what services the child needs.

Seth Bundy, a spokesman for the Missouri Department of Social Services, said the department could not comment on the case, as did Debra Walker, spokeswoman for the state Department of Mental Health.

In Missouri, a child has to be 12-years-old before he or she can be certified to stand trial, said Vivian Murphy, executive director of the Missouri Juvenile Justice Association. Murphy, who said she was not involved with the Kansas City case, said in general, a child in such a situation would undergo a mental health evaluation and that there would be an investigation into the child's living situation.

"It's all about what's best for the 5-year-old," she said. "The family court in Kansas City is going to do a good job of just looking at the circumstances holistically with the 5-year-old and looking at their environment and look at what's going on."