ORLANDO, Fla. -- Notes that Casey Anthony wrote to a fellow inmate that the prosecution did not want the defense to see have been unsealed.

The state attorney's office wanted to wait until their investigation was complete to reveal the notes to the defense.

Now that the defense has copies of the hundreds of pages of letters, they have 15 days to review them and decide whether to object to their release.

The state believes the letters, which were exchanged between Anthony and another inmate in protective custody at the Orange County Jail, contain information that has bearing on the murder case against Anthony, including statements made by Anthony which could be used against her in court.

Orange County Jail policy prohibits protective custody inmates from communicating with each other, but Anthony, possibly with the help of a correctional officer, was able to pass around 50 notes to another inmate.

Investigators tracked down the inmate in January and she turned over the letters, which have been described as relevant, but not a confession.

Investigators interviewed Robyn Adams, a federal inmate who was in protective custody at the jail at the same time as Anthony. She is now serving 10 years in prison for her part in helping her husband, former Altamonte Springs police Officer Clay Adams, run a marijuana growing operation. Clay Adams is also in federal prison.

The Florida Department of Law Enforcement was brought in to investigate, because the state did not want to be accused of misconduct.

The inmate told FDLE "the friendship was not at the request of any law enforcement personnel," but a correctional officer "may have facilitated the communication."

Because Anthony invoked the right to remain silent, anything she told someone working on the behalf of law enforcement would not be allowed in court,

The state will not confirm that Robyn Adams is the inmate who received the notes and letters from Anthony, but a document unsealed on Thursday indicates there are as many as 258 pages of letters that could become evidence against Anthony.

Anthony, who turned 24 on Friday, is charged with first-degree murder in the death of her daughter, Caylee. Caylee was two years old when she was reported missing in July 2008. Her remains were found in December 2008.