Duckett killed herself just hours after being forcefully questioned on the show by Grace over the death of Duckett's 2-year-old son, Trenton, who was reported missing nearly three months ago.
Investigators never clearly figured out where his mother was during the 24 hours before Trenton disappeared. Duckett reported her son missing Aug. 27, telling police she found a cut in his bedroom window screen when she checked on him around 9:20 p.m. She remains the primary suspect in the disappearance, though she killed herself Sept. 8.
Duckett appeared on Grace's show on CNN on Sept. 7. Attorneys for her estate claim Grace's producers said they might be able to help find Trenton.
"We've alleged that Nancy Grace and her producers deliberately misrepresented the reasons for wanting Melinda on the show," attorney Jay Paul Deratany said in a statement. "Within minutes of Melinda's phone interview, it became quite obvious that Nancy's questions weren't about finding Trenton at all, but rather about impliedly accusing Melinda of murdering her beloved son."
"It would certainly seem that not only was Melinda misled by the invitation to appear on the show, but that she was verbally attacked by Nancy Grace," added attorney Kara Skorupa.
Once on the show, Duckett was peppered with questions by Grace about her son's disappearance. Duckett's attorneys allege the public questioning drove her over the edge to suicide.
The lawsuit, which is expected to be filed Tuesday, alleges Grace, her producers and CNN intentionally inflicted emotional distress on Duckett.
"Nancy's insinuations that Melinda had murdered her own child were distressing to an already grief stricken and anguished mother … it was simply more than she could possibly bear," Skorupa said.
CNN Headline News declined to comment specifically on the lawsuit, which seeks unspecified damages.
"We stand by Nancy Grace and fully support her, as we have from the beginning of this matter," a spokeswoman said in a news release Tuesday.
Duckett's son Trenton remains missing. Florida police last week said there's a chance he may still be alive.