The mother of a missing 3-year-old Florida girl pleaded not guilty Friday to charges that she killed her daughter, whose body hasn't been found despite four months of searching.

Casey Anthony's written plea comes three days after a grand jury indicted her on charges of first-degree murder, aggravated child abuse, aggravated manslaughter and four counts of lying to investigators about the disappearance of her daughter, Caylee.

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Caylee has not been seen since June, but wasn't reported missing until a month later. 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.

Casey Anthony, 22, told authorities that she had left her daughter with a baby sitter in June, and that the two were gone when she returned from work. She says she spent the next month trying to find her daughter and didn't call authorities because she was scared.

Investigators immediately started poking holes in her story. The apartment where Casey Anthony said she had left her daughter had been vacant for months, they said. They said she also lied when she told them she had been working at an area theme park as an event planner.

Her attorney, Jose Baez, didn't immediately return phone and e-mail messages Friday. Shortly before the indictment was issued Tuesday, he said he believed his client would be vindicated.

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Click here for some of the documents released.

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