SACRAMENTO, Nov. 8 — Lynette Fromme, banished from her trial for demanding that mass murderer Charles Manson be allowed to testify, was described Friday as yelling in disbelief after an alleged attempt to kill President Ford.

Over defense objections, Secret Service agent Larry Buendorf told the jury Miss Fromme spoke “in disbelief” when she cried, “It didn’t go off. It didn’t go off.”

Describing how he seized Miss Fromme, Buendorf said she shouted the words after he grabbed a .45-caliber pistol she was raising less than two feet from the President in a park outside the State Capitol last Sept. 5.

He did not identify the 27-year-old defendant by name but answered questions during cross-examination in which her name was used.

Miss Fromme was evicted from court twice Friday, once after trying to enter a guilty plea. A federal marshal said she refused to watch the proceedings over closed-circuit television in the marshal’s office.

“Lives will be lost — it’s going to get bloody if they are not allowed to speak,” she shouted after interrupting the prosecution’s opening statement.

U.S District Court Judge Thomas MacBride evicted her again after he asked her if she would stick to the subject of her guilt or innocence and she replied:

“Manson is the only one who can speak for me. My witnesses are Manson and the women, my whole family.”

Manson and four other members of his so-called family are serving life sentences for the 1969 killings of actress Sharon Tate and six other persons.

MacBride later said Miss Fromme would be allowed to return Monday if she promised to behave. But he said she had “forfeited her right” to be her attorney.

John Virga, appointed by the judge to represent Miss Fromme, contended Buendorf was only speculating when he said her tone was one of disbelief. But MacBride said it was a legitimate observation.

Another Secret Service agent, Gerald Kluver, said the woman seized by Buendorf appeared “well under control but surprised” when he went to Buendorf’s aid.

Kluver was not asked to identify Miss Fromme as the assailant.

However, Buendorfs statement that Miss Fromme may have been trying to fire the gun when he grabbed it was shaken when he admitted he didn’t know whether her finger was on the trigger.

In a 10-minute opening statement, U.S. Atty. Dwayne Keyes contended that Miss Fromme had tried to kill Ford out of frustration over her inability to get publicity for Manson.

“She was told the wire services wanted hard news — so on Sept. 5 the defendant gave them hard news,” Keyes said.

Before she was thrown out of court, Miss Fromme told MacBride she had not intended to kill Ford. She added that “the whole purpose of my being here was to get my family a fair trial.”

The judge said she was hurting herself with “bonehead statements” about Manson.

But she insisted, “I can’t put on my defense” without Manson.

Her first disruption came as Keyes was beginning his opening statement.

She approached the judge’s podium and, as Keyes backed away, proclaimed:

“Manson and our family are my own heartbeat. I can’t go to trial unless they are allowed to speak. I’m changing my plea to guilty.”

Earlier in the week, Miss Fromme tried to change her plea to “no contest,” but the move was blocked by Keyes and MacBride. Any action on a plea of guilty is up to MacBride, who did not comment publicly on it.