A U.S. Court of Appeals panel reversed itself yesterday and said that a federal prosecutor assigned to investigate anti-war activists in the late 1960s and early 1970s is immune from a $1.8 million civil suit filed by members of the Vietnam Veterans Against the War (VVAW).

Senior Judge David L. Bazelon wrote in January that Justice Department attorney Guy L. Goodwin, who headed a unit created by the Nixon administration to prosecute crimes by "revolutionary terrorists," did not enjoy absolute immunity as an investigator.

Bazelon said Goodwin could be held liable for damages in a 1973 suit claiming that he had lied under oath during a grand jury investigation into alleged plans by the VVAW to disrupt the 1972 Republican National Convention in Miami.

Bazelon said yesterday that a Supreme Court decision in March that held that witnesses enjoy absolute immunity from lawsuits "compels the conclusion that when Goodwin made his sworn statement from the witness stand he enjoyed absolute immunity" as a witness.

The suit against Goodwin began after a Florida judge asked him under oath if there were government informers in a group of VVAW members fighting grand jury subpoenas. Goodwin said that there were not. One VVAW member, however, was a paid government informer.

The activists sued Goodwin, claiming that their constitutional right to effective legal counsel had been violated because Goodwin's statement led them to discuss legal strategy with their lawyers in the presence of the informer, who passed that information on to the FBI.

Eight of the 12 activists were indicted on conspiracy charges but were acquitted. The other four were convicted of contempt when they refused to testify. The convictions were overturned.

Yesterday's court action reinstates a ruling by U.S. District Court Chief Judge Aubrey E. Robinson Jr., who had dismissed the activists' suit, saying that Goodwin was acting in good faith when he responded to the Florida judge's question.