A father charged with killing his 10-year-old daughter whose body was found in his truck covered in chemicals told authorities the girl tried to poison him by putting baby oil in his soda, according to court documents released late Wednesday.

Jorge Barahona told police that Nubia died at their Miami home, but didn't say how. He said he gave Nubia and her twin brother, Victor, allergy and sleeping medicine to sedate them in the days before Feb. 14, when the children the couple had adopted were discovered in his truck alongside a busy highway.

Nubia's naked body was in the fetal position, drenched in a toxic chemical and hidden in black garbage bags. Her brother Victor was also soaked with chemicals and is recovering from severe burns.

Jorge and Carmen Barahona have pleaded not guilty to first-degree murder and several abuse and neglect charges. Their lawyers tried to seal the evidence before trial, saying it would taint the jury pool. But the state attorney's office in West Palm Beach, where Jorge Barahona's truck was found, released the documents.

Besides saying Nubia tried to poison his soda, Barahona also said he feared she was using rat poison on him and others in the family.

Among the documents is a rambling 2006 letter from Jorge Barahona saying it was only to be read "in case I get sick and past away."

He said he took handfuls of prescription and over the counter medicines "all this pills plus the Benadryl in one day, everyday Sunday to Sunday," according to the letter.

He landed in the hospital and made his wife promise not to tell anyone about his addiction.

Jorge Barahona said he penned the letter in case "some weird result comes up like poisoning," in an autopsy, he wanted to "clear any suspicion on my wife Carmen," according to a letter signed along with fingerprints on Sept. 4, 2006.

Police took carpet samples, a bloody T-shirt, sheets and bags of evidence from the couple's home, where authorities allege the twins were abused for months.

The twins had ligature marks and other injuries indicating abuse and that they had been restrained, according to the documents.

After Nubia's body was found, another brother, who was 11, told investigators that Jorge Barahona beat Nubia with a shoe and Carmen bound her hands and feet and locked her in the tub for days.

The boy said Carmen is nice but "deep in the dark side she's mean," according to court documents.

The boy told a child investigator that Nubia was locked in the bathroom because she "keeps doing mean things to the whole family" and trying to make them go to the cemetery, adding it was difficult to live with a sister like that.

The twins' sister told investigators "she had a family secret that she could not speak of" and stressed that Nubia was alive, not dead. Unprompted by investigators, she also stated "that no one ties anyone's hands or feet and all her father did was take care of Nubia."

Interviews with Carmen and Jorge also indicate why Victor and Nubia may have been singled out from their two other siblings, who were also adopted.

Carmen said Jorge was worried because he thought the twins "were going into my daughter's room and touching her and molesting her."

She said Jorge tried desperately to separate the four children. The other siblings were getting terrible diarrhea and Jorge believed it was because the twins were poisoning them, Carmen said.

"He was obsessed...I want to keep them away from the kids. (Victor and Nubia) are going to hurt the other kids," Carmen Barahona told investigators.

Nubia, who was born with both male and female parts, was molested by her biological father. Carmen Barahona said Nubia begged to be home schooled after classmates found out about her medical condition and were teasing her.

Nubia's death is considered among the worst abuse cases in the state's history and prompted an investigation by the Department of Children and Families to uncover how repeated signs that the children were in danger were missed.

The Barahonas took the twins in as foster children in 2004 and later adopted them. The Barahonas were the focus of a handful of child abuse investigations after school officials alleged Nubia was stealing food and scared of Carmen. The calls were investigated but the allegations were unfounded each time, despite warning signs from teachers and a nurse.

A handful of DCF employees have since been fired, including the child investigator who visited the Barahonas' home in the days before Nubia's body was found.

The agency has since hired 80 new investigators and is making several internal changes, including the way hotline calls are handled and protocol ordering investigators to call police immediately if a child believed to be in danger cannot be located.