SAN DIEGO — A dozen years before David Westerfield abducted 7-year-old Danielle van Dam from her bed, he snuck into the bedroom where his 7-year-old niece slept and fondled her, she testified Wednesday.

"My Uncle Dave had his finger in my mouth and he was kinda playing with my teeth," said the witness, a 19-year-old college sophomore identified only as Jenny N. to protect her privacy. She said she pretended she was asleep initially, but when he put his finger in her mouth again, "I bit him really hard for as long as I could."

Westerfield left the room, she said, but only after he "readjusted" his running shorts.

The accusation came Wednesday, the first day of testimony in the penalty phase of Westerfield's trial. Last week, a jury convicted him of kidnapping and murdering Danielle last February, and prosecutors are now trying to convince the panel to sentence him to death rather than life in prison. Under California law, prosecutors can tell jurors considering a death sentence of prior criminal activity even if no charges were filed.

Prosecutors are apparently hoping the incident with his niece destroys any image of Westerfield, a successful 50-year-old engineer who lived two doors from the van Dams, as a normal man who erred once. During the trial, prosecutor Jeff Dusek said Westerfield hid his demented fantasies about young girls behind a "regular guy" veneer.

Jenny N., a chemistry major at San Diego State University, was clearly torn about taking the stand against her uncle. The pretty blonde with shoulder-length hair was shaking as she walked to the witness chair in platform sandals, a cardigan and flowing white floral-print dress. She described her close relationship with Westerfield's two children, Neal and Lisa, who are expected to beg for their father's life later in the trial, and said she was uncomfortable testifying. Several times as she recounted the incident and her decision to tell police about it, she wiped away tears.

Westerfield, who remained stoic even during the reading of the verdict last week, became slightly animated as his niece testified. When Jenny mentioned that, in spite of her chemistry major, she planned to go to culinary school, he chuckled along with the court gallery. He frequently whispered to the defense investigator and lawyer Robert Boyce as Jenny and then her mother took the stand.

Jenny said her family had gone to a party at the home of her father's sister, Jackie Westerfield, who was then married to the defendant. When the party ran late, she, her younger sister and Lisa Westerfield went to bed in Lisa's room. She awoke some time in the night, she said, to find her uncle kneeling beside her. After he first put his finger in her mouth, he left her and went to her sister, she said.

Jenny said she was not sure what if anything he did to her sister, but he then returned to her side. After she bit him, she said, he stood up went to Lisa's bedside and it was there she saw him readjust the running shorts he was wearing and then exit.

Her mother, identified as Jeanne N., followed her to the stand and said her daughter complained the same night that Westerfield "had been up in the room and had been bothering her."

Jeanne N. said she confronted her brother-in-law immediately and he gave what she thought at the time was a reasonable explanation.

"He said she was fussing in her sleep and he was comforting her," said Jeanne N. The family continued to socialize with the Westerfields, she said.

Police initially found out about the incident from Westerfield himself. In an interview several days after Danielle vanished, an officer asked Westerfield if there was any reason why people might suspect him. In an audiotape of the interview played for jurors Wednesday, Westerfield recalled the incident with Jenny as a misunderstanding between him and his sister-in-law.

"She felt that I had molested her children. I felt really bad about that," he said. He claimed that he went into the room because of a commotion caused when Jenny's foot got caught in her sister's pajama leg.

Remembering Danielle

The rest of the prosecution's case was wrenching "victim impact" testimony. Danielle's parents, Brenda and Damon van Dam, took the stand, as did two of her teachers. Jurors, who have only known Danielle as a silent murder victim distinguished by her DNA and fingerprints, heard about her as a vibrant young girl with a distinct personality.

Brenda van Dam shows jurors schoolwork Danielle completed just before she was kidnapped.

Her teachers painted her portrait in the details of a second-grader's life — learning to read "chapter books," eating in the cafeteria, a "sharing" speech on her family's vacation — and in the hushed courtroom, the mundane activities seemed to take on enormous importance.

Second-grade teacher Ruby Puntennay recalled her final conversation with Danielle, the Friday she went missing. Puntennay said Danielle promised she would complete an essay "about a memory she would never forget" by Monday.

"That Monday never came," said Puntennay.

Damon van Dam smiles while remembering his daughter.

Amy DeStefanie, who taught Danielle in kindergarten and first grade, said, "She got along with everybody. Everyone was Danielle's friend."

When DeStefanie added "She never wanted anyone to feel alone or sad," Damon van Dam, a software engineer who has remained mostly stoic throughout trial, let out a gasp from his seat in the back row and began crying. His wife, who often cried during the trial, appeared shocked and then stroked her husband's head and whispered to him.

On the stand, both van Dams described the horror of their daughter's kidnapping and then the dawning realization that she was never coming home. Brenda van Dam said that, even after police found Danielle's blood in Westerfield's motor home and charged him with murder, she still held out hope.

When searchers finally found her daughter's body, nude and decomposing on a roadside, she had to face the truth and begin planning a funeral, she said.

"We had to pick an urn for our daughter," she said, a sob catching in her throat. That urn remains at the top of the family's staircase, a constant reminder of their loss, Damon van Dam said.

Both van Dams described their sons, Derek, 9, and Dylen, 6, as still reeling from their sister's death. Dylen, Danielle's best friend, had regressed into baby talk and bed wetting. Derek is angry and blames himself.

Brenda van Dam said he once asked her about the night of the kidnapping, "If I had gone to the bathroom, do you think I could have stopped that bad man from taking her?"

Damon van Dam said Danielle's room is still preserved as she left it. Her brothers sometimes play video games among her toys and books.

Danielle van Dam in a photo shown to jurors

Brenda van Dam said she often went into the purple and pink bedroom in search of some connection with her daughter.

"I go in there to cry, to try to feel her, to try to smell her," she said.

During Brenda van Dam's testimony, prosecutors played a videotape of snapshots and home movies of Danielle. The only sounds in the courtroom during the video were the mother's sobs. One juror, a man who cried during the reading of the verdict, turned away, apparently unable to watch the images of a joyful Danielle playing with her aunt at Disneyworld or clowning with her father. One alternate juror cried openly.

When the video ended, prosecutor Dusek asked Brenda van Dam, "Can you describe your loss?"

"I don't know where to begin," she replied.

Westerfield's defense is to begin its case Thursday morning. Defense lawyer Steven Feldman said he will call dozens of witnesses to prove that Westerfield is not "the worst of the worst" and does not deserve the death penalty.