The anxious weeks of preparation and the dreaded trial are over. Now Mormon feminist Sonia Johnson can only wait for her bishop to decide whether to oust her from the church that has been part of her family history for five generations.

"I just feel so tired. I just wish it would be over," she said as she emerged from the three-hour trial shortly before midnight Saturday, fatigue and strain ethed on her face. Johnson's bishop, Jeffrey Willis, who served as both accuser and judge in the church trial, will let her know "in two or three days," she said, whether he has found her guilty of defaming the church.

Despite the trial the night before, Johnson, 43, was in her accustomed place yesterday morning at the keyboard of the organ, playing hymns for the Sterling Park Church of Jesus Christ of Latter-day Saints, where she and Willis are members.

"And she was magnificent!" her mother, Mrs. Alvin Harris, said after the service. Mrs. Harris flew in from her home in Logan, Utah, to be with her daughter and to appear as a witness at the trial. As it turned out, there was no time for Harris' comments, but she was allowed to submit a written statement.

Johnson, mother of four, a sometine college English proessor who writes poetry for a hobby, is accused of undermining the beliefs of her church and its leaders, a charge punishable by excommunication.

She says the charges stem from her activism on behalf of the Equal Rights Amendment and her criticism of the church's tactics in opposing it.

"The question is, will the church allow its members to express their constitutionally protected political beliefs in the public forum, or will it force its 4.5 million members to support selected, ultraconservative politiical causes by threat of excommunication," Johnson said. She spoke to 200 supporters who rallied in the cold and dark outside the church in Oakton, where the trial was held.

Her bishop, the head of a local congregation in the Mormon church, disagreed. In what he emphaasized was a departure from the established practice of not commenting about church trials, Willis issued a statement Saturday night in which he said, "In view of widespread speculation, I wish to say that Sister Johnson's position on the proposed Equal Rights Amendment to the Constitution was not an issue before us" at the trial. Therefore, he ruled out any mention of her ERA activities in the closed trial before himself and his two counselors.

Willis, who by day is a personnel officer for the CIA, has refused any public comment on what the charges against Johnson are.

After Saturday night's session, however, Johnson told reporters that the questions before the church court were, "Was I spreading false doctrine. . . Was I causing people outside the church to think that the Mormon Church was a terrible institution?"

"The things they were trying me about wouldn't have been noticed if it had not been for ERA," she said.

"How can they (the court) understand me if they don't understand what motivated me?"

Her husband,Richard, a statistician, agreed with her that the church's antipathy to ERA was at the heart of the matter. "It was clearly the ERA matter all the way through," he said.

During the earlier session of the trial, which took place Nov. 17, Richard Johnson was not permitted to be with his wife. His exclusion was widely criticized, particularly since Mormons maintain that the husband is the head of the family, even to the extent of approval being sought from the husband before a woman can be asked to accept an honor or an office in the lay-run church.

Richard Johnson, who supports his wife's involvement in the feminist cause, was allowed to be with her Saturday night. Their two older children, however, Marc, 11, and Kari, 14, were forced to wait outside.

Johnson's willingness to defy church authorities on the issue of women's rights has made her an instant heroine to some followers of the dispute. The 200 men, women and children who rallied outside the church, an hour before and througout the trial Saturday night, included people from as far away as Richmond and Pittburgh.

Locked out of the church, they stamped their feet aginst the bitter cold, posed with their banners and vigil candles for photographers, and sang from song sheets that included their own versions of some old standards. One such song went like this:

"Jingle Bells, jingle bells,

Jingle all the way.

What this country really needs

Is a dose of ERA."

While the Oakton Mormon church's doors remained locked to all but the principals in the trial, the adjacent Fairfax Unitarian Church offered a warm oasis and electrical outlets for the coffee urns Johnson's supporters brought.

Among those present were Rep. Patricia Schroeder (D-Colo.) and the Rev. William Callahan, who has recently been disciplined by his Jesuit superiors for challenging the Roman Catholic position on ordination for women.

Esther Peterson, White House comsumer affairs adviser, who is a Mormon, came prepared to offer testimony to the court but was not heard because time ran out.

Within her own church in Sterling Park support is harder for Johnson to find. Yesterday morning's worship session was a testimony meeting, at which individual members customarily give short, impromptu talks about their faith.

"There was a certain amount of tension" as yesterday's meeting began, according to one of those present with unusual emphasis given by the leader on "ground rules" that attempted to exclude comment on Johnson's dispute with the bishop.

"The general theme of those who spoke was praise for the bishopric, for those men of God," said the worshiper.

Near the end of the meeting, Johnson left her place at the organ and took a seat at the front of the chruch in the line with others waiting their turn to speak.

"But just as soon as the man before her finished, and it would have been her turn, the brother who was running the meeting cut it off, with the excuse that they were running out of time," the worshiper said.

"There was a lot of tension, a lot of tension."