LOS ANGELES, Dec. 5 – The girl who turned informer and broke the mystery of the slaying of actress Sharon Tate and at least half a dozen other persons testified today before a grand jury.

Susan Atkins, 21, star witness of the prosecution already has revealed through her attorney many of the gory details of the two-day orgy of murder by the pseudo-religious cult known as the “Manson Family.”

She was the second witness called before the County Grand Jury that is expected to hand down murder and conspiracy indictments against members of the cult next week.

Also on hand to testify was Winifred Chapman, maid at the rented estate of Miss Tate and the person who found the bodies of the actress and four persons last Aug. 9.

Others scheduled to appear were the family of Steven Parent, slain when attempting to drive away from the Tate home after visiting a caretaker friend; Terry Melcher, son of actress Doris Day and an acquaintance of cult leader Charles Manson; and motorcyclist Danny De Carlo, who told officers he had been invited to join the forays of crime by cult members.

Deputy District Attorney Aaron H. Stovitz said he would ask the jury to charge Manson, hypnotic leader of the nomadic band and other unidentified persons with the slayings.

Stovitz carried with him for presentation three enlarged photographs. One was of a long broken-stocked 22 caliber revolver presumably found at the Tate home. Another showed a 34-foot length of nylon rope that, had been looped from the mutilated body of Miss Tate over a rafter and around the neck of hair stylist Jay Sebring. The third was an aerial view of the Tate home in Benedict Canyon.

Miss Atkins’ voluntary testimony about the Tate murders and the slaying of a wealthy couple a day later was believed to be in the hope that she would receive leniency.

It was a cellmate of Miss Atkins who enabled police to, break the case. The woman, Shelley Joyce Nadell, 31, was a confidant of Miss Atkins who later turned informant.

According to Mrs. Nadell’s attorney, Wesley Russell, his client understood the killers believed the stabbings and slashings were supposed to release the “souls of the victims.” She also said Manson’s group killed a total of 18 persons.

“Mrs. Nadell turned over all the names she said she got from Miss Atkins to police,” Russell said. He said she feared for her life because she informed on the group.

Miss Atkins, who faces trial in another murder case which has been linked to the cult, later related her almost unbelievable story to her attorney.

Paul Caruso, her attorney, said she told him the raids on the Tate home and the home of Leno LaBianca, who with his wife was stabbed to death, was directed by the long-haired, bearded Manson.

“A man used a pair of bolt cutters to cut utility lines, then crept around to the side of house, opened a window, and then opened the front door,” Caruso said of the Tate slayings.

The five members of the “family,” dressed in black clothes and wearing black hoods, brought Sharon Tate into the living room of the Benedict Canyon estate.

“Miss Tate became fearful,” Miss Atkins told Caruso. “She tried to make sure her baby wasn’t harmed. She pleaded, ‘Let me have my baby. But they killed her.”

Miss Atkins said the Tate home was “a symbol of rejection” to Manson, who had a grudge against affluent persons because of his troubled childhood.