A court battle that could result in substantial fines for news organizations and jail time for reporters is looming, after lawyers for a former Army scientist investigated in connection with the deadly anthrax mailings in 2001 signaled plans to demand the names of confidential sources for news stories about the anthrax probe.

The scientist, Steven Hatfill, is suing the federal government for invading his privacy by publicly labeling him as a “person of interest” in the crimes and by giving journalists details of his involvement in the investigation.

On Monday, Dr. Hatfill’s attorneys asked Judge Reggie Walton to allow them to issue new subpoenas to reporters who covered the story. In 2004, more than a dozen journalists were called to testify, though a smaller number actually gave depositions.

To stave off a protracted First Amendment fight, Dr. Hatfill’s legal team did not try to force the journalists to identify their sources. Instead, several reporters simply confirmed the government agencies for which the sources worked.

However, last month, Judge Walton told the scientist’s lawyers that they were likely to lose the Privacy Act suit if they did not establish the actual identities of the sources.

Lawyers for Dr. Hatfill and for press organizations involved in the case declined to comment for this article.

Attorneys monitoring the lawsuit said the new subpoenas will likely trigger appeals that could drag out the case for more than a year. “Even assuming the worst case scenario, nobody’s going to jail immediately,” one press freedom advocate, Jane Kirtley of the University of Minnesota, said.

Ms. Kirtley said the reporters, who work for the Associated Press, CBS, CNBC, and others, face an uphill fight because the D.C. Circuit Court of Appeals ruled in 2005 that journalists can be forced to name their sources when an individual sues the government for violating the Privacy Act.

The reporters in jeopardy now are expected to defy Dr. Hatfill’s subpoenas and any court order to name their sources. Ms. Kirtley said one critical issue will be whether Judge Walton imposes fines on the news organizations involved. “That kind of monetary sanction speaks to a corporation the way jailing a reporter would not,” she said.

A First Amendment battle could possibly be avoided: The government and Dr. Hatfill’s lawyers asked Judge Walton to name a mediator to explore a possible settlement of the case.

No one has been charged in the anthrax attacks, which killed at least five people.