REDWOOD CITY, Calif. — Scott Peterson’s father took the stand Wednesday in the penalty phase of his son’s murder trial and described a friendly boy who sang at a senior citizens’ home on Sundays, tutored young students and distributed clothes and food in Tijuana.

“You don’t know who Scott Peterson is, and it’s going to be our job to show you,” defense lawyer Pat Harris said on the second day of testimony in the penalty phase of Peterson’s trial.

“What we’re going to now show you is the 30 years that preceded this. And when we show you those 30 years, I believe that you will agree that this is a life worth saving.”

The attempt to humanize Peterson came a day after Laci Peterson’s mother cried on the stand and screamed at her former son-in-law as prosecutors urged jurors to sentence him to death. Jurors must decide between execution and life in prison without parole.

Lee Peterson said his daughter-in-law’s death and the subsequent trial of his son have taken a heavy emotional toll.

“I’m frightened, deeply saddened,” he said, looking tired on the witness stand. “Losing someone you love and now having our son in such jeopardy — it’s just beyond belief.”

As an infant, he said, Scott Peterson became ill with pneumonia and was placed in a plastic chamber — called a croup tent — that controls humidity.

“It was very risky. The doctor said this may not go so well, but he pulled out of it and he lived,” Lee Peterson said.

He recalled a toddler who was always smiling, enjoyed playing with trucks and action figures, and liked to snuggle while his father read to him.

His son grew into a good student, and captained his high school golf team and dreamed of a pro golf career, Lee Peterson said. He sang to senior citizens, tutored and gave to the poor in Tijuana.

Lee Peterson described his son as motivated and full of energy: “You wouldn’t catch him laying around in bed.”

The day’s testimony was in stark contrast to Tuesday, when Laci’s mother, Sharon Rocha, alternated between tears and outbursts, at times directly addressing her former son-in-law, saying: “She wanted to be a mother. That was taken away from her.”

Lee Peterson’s testimony was somber, and he conceded that by nature, he does not readily show emotion. He and his son exchanged brief glances.

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, 27, 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.

The 32-year-old salesman was convicted on one count of first-degree murder in the death of his wife and one count of second-degree murder.

“We’re not asking you to let this man go free,” said Harris, the defense attorney. “Life without parole is not some sort of a holiday.”