"In this case, the desire on the part of the division (DCFS) to keep the children in their homes overrode the need (to ensure) that children are protected and they have a safe environment," the report said.

This is just one of the complicated considerations facing officials in these cases that involve the community's most vulnerable residents. There are more.

Prosecutors, investigators, social service workers and police say child deaths raise a difficult question: Did the person intend to kill the child?

"You very rarely have quote 'motive,' " said Barlow, who has been involved with a dozen child homicide cases.

"We know people get frustrated," he said. "If someone shakes a child in frustration, I think there should be some accountability but, gosh, is that a criminal act?"

And in investigations of child deaths, there are usually few witnesses to help officials answer that question. Other factors are at play.

Children younger than 3 have rudimentary language skills. The lack of witnesses make it difficult to link the crime to a specific person.

On top of those problems, police detectives receive little, if any, specialized training for child death investigations. So, officers unwittingly fail to gather sufficient evidence of a crime.

Prosecutors, too, may not have much experience with child homicide cases.

The medical findings from an autopsy often muddy the waters for prosecutors. Grey's office may list the cause of death as "undetermined," but there is a crucial disconnect in the way this word is interpreted by prosecutors. Grey, whose office examines the bodies of nearly 200 children younger than 18 each year, says an "undetermined" finding could also mean suspicious.

He said prosecutors could use specific details and opinions about the cause of death from an opinion he renders in his autopsy reports. A badly decomposed body found in a remote area, for example, might be so deteriorated that he can't say what killed the person. But other evidence could indicate homicide.

But prosecutors say that's not reality.

"What the medical examiner has to say is almost tantamount," said Salt Lake County Deputy District Attorney Jim Cope, adding he has never prosecuted a case where the cause of death was undetermined.

"It's an absolute hurdle that if you can't overcome, you can't do it," said former Salt Lake County prosecutor Greg Skordas, who now works as a criminal defense lawyer.