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 had come from the missing girl.
Casey Anthony 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'd found evidence of decomposition in the car.
But what unsettled investigator Carlos Padilla more than Casey Anthony's imprecise information was 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 said.
But Casey Anthony revealed an entire range of emotion in videos of jailhouse conversations between her and her parents, which were released Dec. 5.
In the more than 300 minutes of video released by the Orange County Sheriff's Department, Casey Anthony is shown laughing, crying and growing frustrated with the investigation and her family's questions.
When Cindy Anthony confronted her with Mellich's suspicions that she had had something to do with Caylee's disappearance, her daughter dodged the issue.
"Yuri [Mellich] has it set in his mind. He thinks you've done something to Caylee," Cindy Anthony said to her. At that point, her daughter got up and, when she returned, steered the conversation in a different direction.
Casey Anthony also said that she knows the conversations are being recorded and "there are things [she] directly needs to say" to each of her parents.
When gruesome details about the discovery of Caylee's remains were released in January, Casey's father, George Anthony, nearly committed suicide.