Wichita ? The Kansas child welfare agency has asked a federal judge to dismiss a lawsuit filed by grandparents accusing a social worker of failing to protect a toddler who was beaten to death by her father’s drug-addled girlfriend.

Court papers filed Wednesday by an attorney for the Kansas Department of Social and Rehabilitation Services argue that social worker Linda Gillen had “no duty to intervene” after she investigated a report claiming abuse and neglect of a 23-month-old Coffeyville girl never in state custody.

“We think they are wrong, obviously,” Randall Rathbun, the grandparents’ attorney, said Thursday.

Agency attorney Danny Baumgartner contended that Gillen is entitled to qualified immunity from legal action because she is a government worker, and that she did not violate the grandparents’ constitutional rights while investigating the abuse allegation.

Maternal grandparents Larry and Mary Crosetto sued Gillen in January, accusing her of gross negligence for not protecting Brooklyn. The lawsuit said Gillen did not remove the girl and her older brother from the home despite repeated complaints alleging abuse. The suit does not name the agency as a defendant.

The Crosettos accuse Gillen of acting with “malice and animus” because of a grudge against them connected to their adoption of Brooklyn’s mother, Angela Crosetto Coons, years earlier. The lawsuit does not explain the alleged rift from that time, and their attorney said he could not talk about the case. Brooklyn’s 24-year-old mother died in August 2007.

Brooklyn died on Jan. 20, 2008, as a result of head injuries suffered three days earlier while in the home of her father, Randy Coons, and his girlfriend, Melissa Wells.

The girlfriend, who later married Coons, was sentenced in December to life in prison for the girl’s murder. The father was charged with aggravated child endangerment.