Prosecutors are seeking the death penalty for Robinson, 28, who has been in jail for the past year awaiting trial on charges of murder and aggravated child abuse.
Authorities say she killed her son on December 26, 2015. That day, Robinson's roommate had left their house and returned late in the evening. When he got home, Robinson had blood all over her and the child was missing, according to an affidavit.
Robinson claimed that a relative came to pick up her son, but her roommate remained suspicious.
Once in a while, he told investigators, Robinson went out to the back of the house and stared toward the swamp. At some point, she also began trying to get bus tickets to leave town, the affidavit says.
On December 29, 2015, while Robinson was gone, her roommate went to the back of the house and found a plastic bag with the boy's clothes, shoes and diapers. Then, he saw the suitcase in the swamp and found the child's body inside.
After confronting Robinson, he called 911, the affidavit says.
Robinson, according to the affidavit, immediately confessed to the crime, telling a county sheriff's deputy to put handcuffs on her because she had killed her son. Officials say she stabbed the boy in the abdomen, causing him to bleed to death, and placed a three- to four-inch piece of concrete down her son's throat.
During an interview last month, Powell, the former cellmate, told investigators about a bizarre blood ritual that Robinson had talked about.
"Basically she was in the kitchen and like how you're at a church and, um, something takes over your body and you just kind of go with it or whatever," Powell said. "She said that's kind of how it happened. She just grabbed a knife. She did it to him and then, um, she couldn't control herself."
While in her cell, Robinson also made drawings on the back of her court papers. Powell said she drew a Libra scale that somehow represents the blood ritual.
During their conversations, Powell told detectives that Robinson never once cried about the death of her son and to this day, continues to believe that her son deserved to die.
"She doesn't regret it," Powell said, adding later: "It's sick, it's, she's sick. She's a sick individual."
Powell has been in jail since February 2015. Authorities say that she and her husband killed a woman and nearly beat to death another. The couple's young children witnessed the alleged crimes. Powell is charged with murder, attempted murder and child abuse.
Robinson is scheduled to return to court in February.
Prosecutors filed a notice of intent to seek the death penalty in January 2016, the same month that the Supreme Court found Florida's death penalty system unconstitutional because it does not give jurors enough power in deciding whether to impose the death penalty.
Florida state law required judges to make the final decision on whether a defendant is sentenced to death.
Citing the high court's ruling, Robinson's defence attorney questioned the validity of the death penalty as punishment. But prosecutors argued that a new bill addresses the issues raised by the Supreme Court. House Bill 7101, signed into law by Governor Rick Scott (R), overhauls the state's death penalty system by requiring that at least 10 of 12 jurors must recommend execution.
