A utility worker discovered a child's skull Thursday less than a half-mile from 3-year-old Caylee Anthony's home in some woods that, until recently, had been flooded. The remains could solve a six-month-old mystery of where the girl went, legal experts said.

Caylee's mother, 22-year-old Casey Anthony, was indicted in October on first-degree murder and other charges, even though the toddler's body hadn't been found. She has insisted that she left the girl with a baby sitter in June, but she didn't report Caylee missing until July.

"If the defense had been able to go to trial without a body being discovered, hopes for reasonable doubt might have been compelling. If the body proves to be Caylee, then it immediately becomes an uphill case for the defense," former U.S. Attorney Kendall Coffey said.

There was nothing that immediately indicated the skull found Thursday was Caylee's. But Orange County Sheriff Kevin Beary said his investigators and the FBI would work around the clock and through the weekend to identify the child.

They were seeking yet another search warrant for the home where Caylee and her mother lived to look for more clues. There are also no other similar missing-child cases in the area.

"Now the investigation continues," Beary said. "There is a lot of lab work to do. There is a lot of DNA work to do. There is a lot of crime scene work to do."

Prosecutors announced last week that they would not seek the death penalty against Casey Anthony. Even if the remains are Caylee's, law experts said it was unlikely the state would reverse its decision because prosecutors still have not determined a motive.

And depending on what the evidence yields, the discovery could also help defense attorneys.

"If the body was tampered with, if wild animals got to it, if the evidence they get with it is contradictory in some way, then the job (for prosecutors) just got tougher," said Jim Cohen, a law professor at Fordham University in New York.

"This can verify or help to verify their theory: that the child was killed when the prosecution thinks she was killed," said Richard G. Lubin, a criminal defense lawyer based in West Palm Beach. "But until you do some of this scientific work, we don't know what it's going to show."

A spokeswoman with the state attorney's office said Thursday that officials wouldn't comment until the investigation was complete.

For the past several months, Anthony's family, police and volunteers from around the country have searched for the little girl.

Casey Anthony has insisted that she left the girl with a baby sitter in June, but she didn't report her missing until July. She was told about the discovery in jail on Thursday, and was placed under psychological observation _ not suicide watch. Her attorney, Jose Baez, visited her and did not return calls seeking comment.

The child's grandmother first called authorities in July to say that she hadn't seen Caylee for a month, and that her daughter's car smelled like death.

Police immediately interviewed Anthony and said that everything she told them about her daughter's whereabouts was false. The baby sitter was nonexistent, and the apartment where Anthony said she had last seen Caylee had been empty for months. Anthony also lied about where she worked.

As the case unfolded, troubling details emerged: Photos surfaced of Anthony partying after her daughter went missing. Friends said she was a habitual liar, but also a good mother.

Last month, the Orange County State Attorney turned over almost 800 pages of documents, which showed someone at the Anthony home had done Internet searches for terms like "neck breaking" and "household weapons."

In mid-March, someone used the Anthonys' home laptop to search Google and Wikipedia for peroxide, shovels, acetone, alcohol and chloroform. Traces of chloroform, which is used to induce unconsciousness and is a component of human decomposition, were found in the trunk of Casey Anthony's car during forensic testing, the documents said.

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Associated Press Writers Tamara Lush, Suzette Laboy, Damian Grass, Sarah Larimer and Antonio Gonzalez in Miami contributed to this report.