In the suit filed Tuesday, Kline alleged that Robert Mendoza and Tali Walters of Cambridge (Mass.) Forensic Consultants got a release from Rader "for the sole purpose of financial, professional or personal gain."
Mendoza videotaped an interview with Rader, part of which "Dateline NBC" broadcast Aug. 12.
The Sedgwick County, Kan., suit does not say the TV show paid for the tape, nor does it detail how Cambridge profited, the Wichita (Kan.) Eagle reported.
Kline asked for an injunction, more than $75,000 in damages and the return of all documents -- including videotapes -- on loan to Cambridge.
While Mendoza told the newspaper in August he neither supplied nor made money on the tape, he declined comment on Tuesday's suit.
Steve Cavanaugh, attorney for Mendoza and Walters, said he did not know the tape's whereabouts.