CAMBRIDGE -- Justin Bealer, 28, of Colona, waived a jury trial on Monday and began a bench trial before Judge Charles "Casey" Stengel.

Mr. Bealer is being tried on 15 of the 79 counts of Class X felony predatory criminal sexual assault he was charged with on Nov. 12, 2010.

In August, he was found guilty of eight counts Class 2 felony aggravated criminal sexual abuse and nine counts Class X predatory criminal sexual assault. He has not yet been sentenced on those charges.

On Monday, a 17-year-old girl testified she began going to Mr. Bealer's house when she was in the fourth grade so he could babysit her. She said that when she was in the fifth grade, Mr. Bealer began his sexual conduct, with one type of act happening at least 30 times and another happening at least 50 times.

She testified Mr. Bealer ostensibly was giving her music lessons but, if she hit a wrong note, he would have her pull a piece of paper from a box and do what was written on it. Some of the tasks were innocent but some were sexual, she said. The girl also said Mr. Bealer often gave her money, took her to a park or swimming.

Mr. Bealer's attorneys, Marc Wolfe and Jacqueline Aldrich, challenged the girl's credibility and memory of which rewards followed which alleged acts.

The girl said Mr. Bealer's conduct continued through the summer of her sixth grade year, but then she stopped going to Mr. Bealer's house. She said she didn't tell her mother about the acts until she realized Mr. Bealer was being charged with sexual assault to another child. That case was filed on Nov. 5, 2010.

Also on Monday, Corey Peck, of the Illinois State Police, testified he was present when Mr. Bealer was interviewed about the charges, and police searched his grandmother's home where he lived. Agent Peck said Mr. Bealer told Agent Tony Romeo he had had a sexual relationship with two girls. When by his grandmother if the allegations were true, Mr. Bealer responded "yes," Agent Peck said.

Agents took a laptop computer and Sony camera from the home, the agent said.

The bench trial is expected to conclude today.