On the tape, she is heard frantically telling emergency operators, "I can't find my granddaughter. ... There's something wrong. ...I found my daughter's car today and it smelled like there's been a dead body in the damn car." Casey Anthony then got on the phone and reported she may have a missing child.
Cindy Anthony later retracted that statement, saying that the smell in the car could have been from garbage.
As investigators would quickly learn, this would only the be first of many twists and story changes in the curious case.
CLICK HERE for a timeline of the case.
Since their investigation was launched on July 15, some Orange County officers have become well acquainted with the frustrations of following leads based on incomplete information, half-truths and what one officer said were "smoke bombs."
In the original version of events, Caylee's mother reported her missing to police, saying she had dropped the child off at a babysitter's house on June 9. When she went to pick the child up, both the child and the baby sitter had disappeared.
Casey's parents both corroborated the story until a bond hearing on July 25 when Cindy Anthony said that the last time she saw the child was not on June 9, but on June 15, and that she had just been confused.
When police questioned Casey Anthony about her daughter prior to her arrest, they say Anthony misled them multiple times.
When she took police to the apartment where she said the babysitter, Zenaida Fernandez-Gonzalez, lived, they found that no one had lived in the apartment for five months.
At that time, lead investigator Yuri Mellich said, "I am not disregarding that this person may or may not exist, but Casey Anthony's friends and family have never met this person."
After an extensive search for Gonzalez, a woman with the same name came forward in September to tell authorities she had never met Casey or Caylee. Police cleared her of any involvement.
In a report released Wednesday, Mellich said that "after several months of investigation, detectives could find no one who has ever met, spoken with or seen any Zenaida Gonzalez who had cared for Caylee Anthony."
Casey also claimed to have worked for Universal Studios, but admitted later that that was not true.
Scientists found evidence of body decomposition and traces of chloroform in Casey Anthony's car trunk, according to forensics reports released in October.
Lab reports from the FBI found that a hair strand in the trunk showed "characteristics of apparent decomposition." The hair is "microscopically similar" to hair strands found on Caylee's brush, but the report said it could not conclusively say the hair in the trunk came from the missing girl.
Casey had been considered a "person of interest" in her daughter's disappearance since mid-July after police reported in a bond hearing that they believed they found that evidence of decomposition in the car.
But what unsettled investigator Carlos Padilla more than Anthony's imprecise information is her overall attitude.
"She has shown no emotion," Padilla told ABCNews in July. "That's unusual. At the time of the interviews ... she didn't seem concerned and that made this case much stranger."
"She spoke to deputies like she was talking about baseball. How do you get through to someone like that?" he added.