Melinda Duckett committed suicide Sept. 8, a day after Grace's show on CNN Headline News aired a segment in which Grace grilled Duckett about her whereabouts Aug. 27 — the day 2-year-old Trenton Duckett was reported missing.
Authorities, who said last week they believe the boy is alive, have named Melinda Duckett as the prime suspect in his disappearance.
Jay Paul Deratany, the attorney representing Duckett's estate, said Tuesday that Grace encouraged Duckett to appear on her show by saying the goal was to draw public attention to help find Trenton.
"It's not just about the questioning, it's about the misrepresentation with the knowledge that she was emotionally distraught," Deratany said. The attorney said Grace improperly took on the role of a law enforcement officer.
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.