The 9-year-old boy held the prosecutor's hand on the way up to the stand and greeted Deputy District Attorney Mark V. Tranquilli by saying, "Hi, T-Rex" -- his nickname for him.

And that was the last light-hearted thing he said.

The third-grader testified Thursday in the death-penalty trial of William L. Page, of Braddock, who is accused of killing his 2-year-old daughter, Nyia, on Feb. 3, 2007.

Mr. Page is also on trial for molesting the boy, who lived in the home at the time.

Mr. Tranquilli called the child to testify about what happened to him the night before Nyia disappeared.

The boy walked the jury of seven men and five women through story time and when he got into bed.

"Did anything wake you up that night?" Mr. Tranquilli asked.

"Will. Will was lying down on the floor. He touched me where he's supposed to not be."

Mr. Page touched the boy on top of his pajama pants, he told the court, making him feel "sad."

The boy told Mr. Page to stop, but then, he testified, the man covered his mouth with his other hand.

"Then he just ran out of the room."

The boy didn't tell anyone until the next day -- after Nyia was reported missing, and he was interviewed.

Mr. Tranquilli finished his questions by asking the boy about telling the truth.

"Do you know the difference between the truth and a lie?"

"Yes," he answered.

"Is it good or bad to tell the truth?" Mr. Tranquilli continued.

"Good."

"Is it good or bad to tell a lie?"

"Bad," the boy responded.

"When you were bad, what would happen?" the prosecutor asked.

"Will would hit me with a belt."

On cross-examination by defense attorney Christopher Patarini, the boy's answers were less clear.

"You don't remember what happened on that date, right?"

"Yes."

"You want to do what they want you to say, right?" Mr. Patarini continued.

"Yes."

"You just cannot remember what happened when Nyia disappeared, right?"

"Yes," the boy answered.

But later, in what he said was an effort to repair the child's credibility, Mr. Tranquilli called Allegheny County Detective Gregory Matthews, who had observed the forensic interview with the boy the day Nyia disappeared.

The boy, who was only 6 at the time, was quiet and scared at first, the detective said.

"He was preoccupied with Nyia, his angel -- that's what he called her -- was missing," Detective Matthews said.

Later using furniture from a child's dollhouse, the boy reconstructed the scene with Mr. Page at his bed the night before, the detective testified.

Detective Matthews said the boy related the incident two times.

"A third time [the interviewer] asked him, and he broke down and cried and put his head down."

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