A federal judge here yesterday cited the law, trial testimony and two lines of a Sir Walter Scott poem to uphold the 1972 dismissal of a first-year D.C. police officer who was fired after publicly supporting a "blue flu", or police "sickout", during a pay raise dispute.

U.S. District Judge Louis F. Oberdorfer said the officer, James R. Tygrett, had so damaged his credibility at the time by indicating he would falsely claim he was ill so that he could participate in a "blue flu" action that any testimony he might have to give in a criminal case as a police officer would be subject to challenge.

In discussing Tygrett's credibility, Oberdorfer said the officer's public willingness to report falsely that he was too sick to work placed him in the web of deceit in Sir Walter Scott's "Marnion":

"Oh, what a tangled web we weave, When first we practice to deceive!"

Attorneys for Tygrett claimed his dismissal violated his First Amendment right of free speech.

Oberdorfer, however, ruled that in weighing the balance between free speech and the public interest in essential public services, including "believable" police officers, Tygrett's dismissal was legal.

Tygrett was fired six years ago today after making statements to the press as a spokesman for dissident young police officers concerning congressional inaction on a pending police and fire department pay raise. He repeated his statements - calling for a planning a "blue flu" job action - to a depty police chief investigating the news reports.

The police official recommended that Tygrett, who was only two weeks away from completing his probationary period, be fired because he would "knowingly and purposely depart from the truth to achieve his goal."

During the trial before Oberdorfer, Tygrett said he admitted he made the statements but said he never intended to go through with the "blue flu" threat. He said he made them because they would "attract public attention . . . and stimula* te congressional action," and lied about them to the police official out of concern that the police official would make his true intentions public and discredit him in the eyes of his supporters among police and the public.

Oberdorfer said a good reputation for truthfulness is essential to a police officer, and a lack of credibility might harm any testimony an officer might give in court.