A frail-looking Jackie Peterson (search) tearfully pleaded with jurors Wednesday to spare her son's life, saying that "if you were to take Scott away from us ... we would lose a whole family."

"It would be like Laci never existed," she said, crying so hard at times she was unintelligible.

While defense lawyers flashed Peterson family photographs on a large screen, Jackie Peterson, who uses a portable oxygen tank for a lung ailment, begged jurors to see the good in her son.

"He's an exceptional young man and he's my son," she said. "I know he's not perfect ... but he is genuinely a loving, caring, nurturing, kind, gentle person."

Scott Peterson (search) wiped tears from his eyes as his mother testified.

Defense lawyers are trying to convince jurors that Peterson deserves life in prison, not the death penalty.

The 32-year-old former fertilizer salesman was convicted Nov. 12 of two counts of murder for killing his pregnant wife, Laci, and her fetus.

Prosecutors say he killed Laci in their Modesto home on or around Christmas Eve 2002, then dumped her body into San Francisco Bay. The remains of Laci and the fetus were discovered about four months later near where Peterson claims to have been fishing alone the day his wife vanished.

During her 40-minute testimony, Jackie Peterson also described for jurors how her father was murdered when she was a child and her mother was an invalid who couldn't take care of her and her two brothers, so they were sent to an orphanage.

"We knew that God loved us and that just took over everything," she said, adding that her own health has deteriorated in recent years because of stress.

"My life is hard," she said.

Jackie Peterson's testimony was expected to conclude the defense's case in the penalty phase of Peterson's trial. Defense attorneys have called 36 witnesses over seven days in the penalty phase. Prosecutors called just four of Laci's family members on the first day Nov. 30.

Judge Alfred A. Delucchi (search) told jurors, who were dismissed midday Wednesday after Jackie Peterson's testimony, to expect closing arguments and the start of deliberations Thursday.

Earlier Wednesday, a family friend broke down in tears when asked how a death sentence for Peterson would affect her life.

"It's just going to be an extremely sad day if that's what happens. It's not going to bring back Laci and it's not going to bring back Conner. All it's going to do is add another tragedy," said Shelly Reiman, who first met Scott and Laci Peterson (search) while the couple attended college in San Luis Obispo.

"The Scott I knew is a very gracious, caring person," Reiman said.