An investigator working with an intelligence-gathering office in Washington State placed the names and photos of antiwar protest organizers into a domestic terrorism file, according to an amended complaint filed on Monday with the Federal District Court in Tacoma.

Those papers added the investigator as a defendant in a lawsuit that began in 2010 after it emerged that John J. Towery, a civilian employee of the Army, had used a fake name to infiltrate and spy on antiwar groups. Much of the case has been based on a continuing series of public information requests filed by activists, which have yielded hundreds of pages of documents.

The investigator, Chris Adamson, was described by plaintiffs as a member of the Pierce County Sheriff’s Department and a director of regional intelligence groups with the Washington Joint Analytical Center, which became the Washington State Fusion Center, one of dozens of counterterrorism offices financed by the Department of Homeland Security.

Mr. Adamson helped coordinate Mr. Towery’s spying efforts and listed at least four protesters in a “national domestic terrorist database with pictures, and identifying personal information along with false claims alleging a propensity for violence,” the lawsuit said.