REDWOOD CITY -- Laci Peterson's mother took the witness stand Tuesday in the penalty phase of Scott Peterson's murder trial, rising out of her seat and screaming at her former son-in-law that he should not have killed his pregnant wife.

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"She wanted to be a mother. That was taken away from her," Sharon Rocha yelled directly at Peterson, her voice rising and cracking. "Divorce was always an option -- not murder."

Her sudden outburst was loud enough to make several jurors jump. Peterson, convicted Nov. 12 of murdering Laci and the eight-month-old fetus she carried, watched her and had no visible reaction. At one point, he dabbed his eyes with a tissue.

Rocha, wearing a gold, heart-shaped pendant with a picture of her daughter on it, took the stand on the opening day of the penalty phase. Laci's older brother, Brent Rocha, younger sister, Amy Rocha, and stepfather Ron Grantski testified before her.

Throughout the testimony, prosecutors displayed photographs of Laci, including one from Mother's Day 2002. Taken a week after Laci's 27th birthday, the picture showed three generations of women -- Laci, her mother and her grandmother.

Mother's Day, Sharon Rocha told the jury, would never be the same.

"The first Mother's Day (after her death) I laid on the floor and I cried most of the day because she should have been there," she said, sobbing on the stand.

Her voice echoed in the courtroom, her chest heaving as she fought back tears.

"I can hear her giggling," Sharon Rocha said, gazing at a larger-than-life image of her daughter displayed on a white wall screen. "She didn't just smile, she would giggle. She would kind of bend over when she would laugh."

Jurors will recommend whether the 32-year-old former fertilizer salesman should be executed or get life in prison without the possibility of parole for the 2002 murders. He was convicted on one count of first-degree murder in the death of his wife and one count of second-degree murder for the killing of her fetus.

Peterson's defense attorney, Mark Geragos, did not question any of the witnesses. Prosecutors concluded their case after testimony from just the four family members. Defense attorneys will begin their case Wednesday.

In their opening statements, prosecutors said the death of the 27-year-old substitute teacher left a hole in her family's hearts "that can never be repaired."

Prosecutor Dave Harris described the case like "ripples on water."

"When the defendant dumped the bodies of his wife and unborn son into the bay, those ripples spread out and they touched many, many lives," Harris told jurors.

The only appropriate punishment, he said, is death.

Laci Peterson's siblings recounted how much she meant to the family and looked forward to being a mother.

Laci's sister, Amy Rocha, recalled how Laci planned her 21st birthday and "made it perfect." She also described her feelings as she and others searched for her sister after she was reported missing on Christmas Eve 2002.

"Scared -- I don't know how to describe it. It was just the worst thing you could think about, like a nightmare," Amy Rocha said, her lips curved firmly downward in a tight frown.

Brent Rocha said he has tried to remember the good times they shared but those memories are "overshadowed all the time by how she died ... and maybe her knowing who did it."

Prosecutors claim Peterson strangled or smothered his pregnant wife in their Modesto home on or around Christmas Eve 2002, then dumped her weighted body into San Francisco Bay. The remains of Laci and the fetus were discovered four months later along a shoreline a few miles from where Scott Peterson claims to have been fishing alone the day his wife vanished.

Brent Rocha recalled how he and his sister had a sometimes antagonistic relationship when they were young but grew closer as they got older. Rocha, who has two sons, said he and his sister looked forward to their children playing together.

"I don't think I've ever heard her be more excited than the day she called me up to tell me she was pregnant," he said, describing Laci as "the centerpiece of the family ... She was the one who brought everyone together."

Laci's stepfather, Ron Grantski, bit his lower lip and paused occasionally to sigh as he described the loss.

"I miss the grandson that we were supposed to have," Grantski testified, adding that Laci "lit up every room. She was always the center of attention."

Asked how Laci's death has affected the family, Grantski paused and looked down.

"It's awful hard to talk in front of a bunch of people about things that are very personal," he said. "I don't know if any of us will able to be the same again."

Sharon Rocha's testimony was the most emotional of the day, as she described the painful days after Laci vanished.

"I didn't sleep in my bed for weeks. I couldn't get comfortable and warm not knowing where she was," Sharon Rocha said.

Rocha then lashed out at Peterson again with a shriek.

"Laci always had motion sickness ... and you knew that, and you put her in the bay. You knew she'd be sick for the rest of eternity and you did that to her anyway," she yelled, sobbing uncontrollably.

"Every morning when I get up I cry," she added. "It takes me a long time just to be able to get out of the house ... I miss her. I want to know my grandson. I want Laci to be a mother. I want to hear her called mom."