Family members have said Simms was suffering from mental illness. She was hospitalized after her son's death, and had been hospitalized for a brief period in the months beforehand.
Simms' mother, Vontasha Simms, said she was "totally flabbergasted" by the decision to bring criminal charges.
"No one in their right mind is going to sit out there for two days in the elements," she said, noting that her daughter was exposed to the weather and had no food or water, either, during those two days.
She said her daughter had just begun taking medication for her mental-health problems a couple of months before, and wondered whether there were problems getting the right medication or dosage. She said her daughter had been complaining of headaches before Ji'Aire's death.
"Somehow, somewhere within that episode, time stopped for her," Vontasha Simms said.
Vontasha Simms said she hopes to retain a private attorney to represent her daughter, but worries that she can't afford it.
Christopher Slobogin, a professor at Vanderbilt University's law school and an expert in mental health law, said prosecutors have leeway in deciding whether to bring criminal charges in cases like this. How much Simms' apparent mental illness affects the case depends on how strong the defense's argument is that she is ill, Slobogin said.
"If she's pushing her dead child in a swing that's pretty good evidence of serious impairment," Slobogin said.
After Monday's arraignment, Covington said he didn't know whether he might revisit the criminal charges if subsequent mental-health evaluations raise questions about Simms' sanity or competency. While he acknowledged that mental-health issues are part of the case, he said it would be up to the defense to bring forward a mental-illness defense.
He said he could not discuss specific facts of the case, including whether Simms had offered an explanation of her behavior to the authorities.
Earlier this year, the boy's father petitioned a District of Columbia court for custody of his son, saying Simms was behaving erratically and jumped out of a moving taxicab with Ji'Aire.
In court papers, Simms acknowledged she had had a mental breakdown but insisted she was doing better.
"This breakdown that I had was the first that I have ever had in my life and I truly believe it was from an extreme amount of stress weighing heavy on me. I am now in a much better productive space," she wrote in a letter to the judge.
In May, just days before Ji'Aire's death, a judge ordered the parents to share custody, and court records indicate both Simms and the boy's father agreed to the arrangement.