Sarah T. Hughes, the woman who swore in Lyndon Johnson as President on board Air Force One, has developed into an activist federal judge, both beloved and begrudged in Texas.

Now 81 and still setting legal precedents here, Hughes wastes little time reminiscing about her moments in the national spotlight 14 years ago.

Asked about the Kennedy assassination, she snaps, "I've already given out that information." Irritated by the inquiry, she rushes over to her secretary's desk and produces a three page, typewritten summary of her recollections.

Hughes' quick steps across her chambers are surprising, for her face is as creased and lined as the judicial robes draped over her 5-foot frame.

It was John F. Kennedy who appointed her to the federal bench in 1961 - over opposition from the American Bar Assn. that Hughes, then 65, was too old for the job.

Two years later, when Kennedy was shot, Hughes was at the Dallas Trade Mart waiting "in vain" for the President to come speak.

When she phoned the courthouse at 2:15 on Nov. 22, the U.S. attorney reached her with the message that "the Vice President wants you to swear him in as President."

In 10 minutes, Hughes arrived at the airport, only to find that police had blocked the area leading to the plane.

"But there was no difficulty. They knew me," she recalls.

Inside Air Force One, Hughes embraced both LBJ and Lady Bird, friends since her years as a state judge. When introduced to Jacqueline Kennedy, Hughes told the widow, simply, "I loved him very much."

A small, soft leather Bible was thrust into her hand. "Someone said it was a Catholic Bible," she says in her official recollections. ". . . I would like to think it was, and that President Kennedy had been reading, it on this, his last trip."

Today Hughes is best known in Dallas for her five-year battle against the county commissioner over conditions at the local jail. Although the jail is just 11 years old, Hughes has ruled it obsolete and ordered a new facility constructed.

When the jail was opened for public tours prior to a recent bond election, about 500 sightseers showed up to see if the jail was "as bad as Sarah says it is."

Hughes is now supervising plans for a new $49 million jail complex that the local press is calling "the jail Sarah built."

So adamant is Hughes over the jail issue that she appears on TV news shows, wearing conservative suits and low-heeled pumps, to explain her rulings.

Unlike other judges, she isn't concerned about off-the-bench remarks compromising her position. "Everybody knows my opinion," she remarks.

A widow since 1964, Hughes swims 10 to 30 laps a day, practices yoga morning and evening and rides her bicycle on weekends. Last September, People magazine photographed the spry judge standing on her head.

This month Hughes will hold court in the Panama Canal Zone for a week. She also attended the National Women's Conference in Houston last month, lecturing on her political career.

Sarah Tilghman Hughes first spoke out for feminism in 1912 when she debated women's suffrage at Western High in Baltimore, where she was born and raised.

Her concern over prisoners' rights, particularly juveniles, was shaped during a stint as a D.C. policewoman, a job she held while attending George Washington University law school in the early '20s.