McLEAN, Va. - A federal judge yesterday dismissed a libel lawsuit filed against the New York Times by Steven Hatfill, a former Army scientist once identified as a person of interest in the 2001 anthrax-by-mail attacks.

U.S. District Judge Claude Hilton in Alexandria dismissed the case a week after Times lawyers argued that Hatfill should be considered a public figure under libel law, which makes it much more difficult for a public figure to win a judgment than a private citizen.

The judge did not explain his ruling.

Hatfill had contended that a series of columns by Nicholas Kristof had falsely implicated him as the culprit in the anthrax attacks.

His lawyers had argued that even if Hatfill qualified as a public figure, they could still prevail at trial because they had uncovered serious flaws in Kristof's reporting.

Times lawyers argued that Hatfill qualified as a public figure because he had injected himself into the national debate about bioterrorism years before the anthrax attacks. He had occasionally been quoted as an expert in the media, and even donned a chemical suit once for a magazine photo.

Times spokeswoman Catherine Mathis said the paper was pleased with the ruling. Hatfill's lawyers could not immediately be reached for comment.

This is the second time that Hilton has tossed out Hatfill's claim against the paper.

Kristof said all along that he never intended to accuse Hatfill but simply wanted to prod a dawdling FBI investigation.

Hatfill is also suing former Attorney General John Ashcroft, the Justice Department and others, alleging that they violated his civil rights.

Five people were killed and 17 sickened by anthrax mailed to lawmakers on Capitol Hill and news-media members in New York and Florida just weeks after the Sept. 11 attacks. The case remains unsolved.