Scott Peterson (search) fit in well with his classmates and never caused any problems, a former principal at his middle school testified Monday at the penalty phase of the former fertilizer salesman's double murder trial.

Peterson, convicted in November of first-degree murder in the death of his wife Laci and second-degree murder for the death of her 8-month-old fetus, was "a fine school citizen," Ronald Roger Rowe said on the fifth day of the penalty phase.

Jurors must decide whether Peterson will be sentenced to death or to life in prison.

"Scott was a young man in whom I had great confidence and nothing that I can envision then or now would suggest to me that the death penalty is appropriate for him," Rowe told the jurors.

Peterson's friends and family have described him as a loving son and generous person, someone who never laid a hand on anyone.

Also on the witness stand Monday was Marvin Threatt (search), former dean of students at Peterson's high school in San Diego, who said Peterson never caused any problems and volunteered for charities.

Students were given a break during the school day to perform charity work, Threatt said.

"Many students would not come back to school on time," he said. "The thing I recall mostly about Scott is that he did always come back on time. He was never late."

Prosecutors claim Peterson smothered or strangled Laci 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 about four months later along the bay shore, a few miles from where Peterson says he was fishing alone the day she vanished.

Legal experts say the defense is using a well-planned strategy to persuade jurors to spare his life.

"I think they're basically asking the jury to identify not with Peterson but with the people who care about him," Loyola Law School professor Laurie Levenson said.

But a former prosecutor says the strategy could backfire.

"In the end, if jurors really believe he did it, then every day the defense puts on evidence of him being harmless and kind and patient, it makes Laci look like an even more vulnerable victim," said Jim Hammer, a former San Francisco prosecutor who has been following the trial.