Casey Anthony (C) smiles at Defense Counsel Cheney Mason and Dorothy Clay Sims, before her sentencing at the Orange County Courthouse in Orlando, Florida, July 7, 2011. Reuters

Casey Anthony killed her daughter and had sex with her defense lawyer in exchange for legal services, according to court documents filed in Florida. Anthony, who represented by attorney Jose Baez, was acquitted in 2011 of her daughter's murder. Baez has denied that he had a sexual relationship with the Florida mother, according to media reports published Wednesday.

The allegations from private investigator Dominic Casey are laid out in a Chapter 7 bankruptcy filing submitted to the U.S. Bankruptcy Court in Tampa in April. Casey, who worked for Baez, claims the lawyer told him in July 2008 that Anthony murdered her daughter and "dumped the body somewhere, and he needed all the help he could get to find the body before anyone else did." Casey resigned from the case a few months later.

Casey detailed in the documents how he once found Anthony naked in Baez's office. Casey "told (Anthony) that she cannot allow (Baez) to continue engaging in this behavior," the investigator wrote in the affidavit. "Casey told me she had to do what Jose said because she had no money for her defense." The documents claim Baez demanded oral sex for organizing media interviews. ABC News published the court documents here.

Baez told People magazine the allegations were untrue. "I unequivocally and categorically deny exchanging sex for legal services with Ms. Anthony," he said. "I further unequivocally and categorically deny having any sexual relationship with Ms. Anthony whatsoever."

Anthony was arrested in 2008 for child neglect after her 2-year-old daughter, Caylee Anthony, went missing. The child was last seen on June 16, but authorities weren't notified until July 15. The child's body was later found near the family's home in Orlando.

A Florida jury eventually found Casey Anthony not guilty of killing her daughter, but she was convicted on four counts of lying to authorities, providing fuel to critics, who insisted she was responsible for the death of her only child. Prosecutors claimed during the trial that she killed Caylee by using chloroform and smothering her nose and mouth with duct tape. They alleged that she then hid the body in the trunk of her car and dumped it in the woods.

Anthony was 26 years old when she filed for bankruptcy in 2013, citing almost $800,000 in liabilities. The documents claim she owed Baez $500,000 for his role in her defense trial.