PARIS, Maine — Testimony began Tuesday morning in Oxford County Superior Court into the case of a Rhode Island man accused of sexually assaulting a 13-year-old girl in Hanover two years ago.

Kyle C. Sanville, of West Kingston, R.I., was indicted in August 2012 on a charge of gross sexual assault of a person under the age of 14. The 24-year-old Iraq war veteran, who works in Rhode Island as an EMT and volunteer firefighter, pleaded not guilty to the charge in October 2012.

According to court testimony, the assault occurred in late November 2011 at a home in Hanover after he had gone out drinking with friends. The incident was discovered five months later by school officials who intercepted the girl’s Internet postings which described the incident.

“You are the fact-finders,” active retired Justice Robert W. Clifford told the jury of 15 women and one man as he instructed them on how the trial would proceed and what their role was during the trial.

In his opening statement, Oxford County Assistant District Attorney Richard R. Beauchesne told the jury that to convict Sanville, they must prove Sanville and the girl engaged in a sexual act; that the girl was not his spouse and that she had not attained the age of 14 at the time of the sexual act. Because two of the points were proven without question, the crime boiled down to a statutory crime, where the girl does not have to prove compulsion, force or that the sexual act was done against the will of the victim, Beauchesne said.

In his opening statement, defense attorney Kevin Joyce called Tuesday, “the most important day for Mr. Sanville.” Joyce told the jury that Sanville “has an absolute right to be presumed innocent” throughout the deliberations.

“The entire burden (of proof) is on the state,” Joyce said as his client sat up straight, watching the jury’s reaction.

During more than an hour of testimony, the girl’s mother said she first learned of the assault when she received a call from her daughter’s school, asking that she come in. Surrounded by four or five school officials, including a guidance counselor and information technology staff, the mother said she was shown evidence of blogs the daughter had posted that indicated her daughter had had sexual intercourse with Sanville.

“I was completely in shock,” she said of the meeting, which she called “intimidating.”

The mother said she called her husband and had a “horrific” conversation with him, and then they both approached their daughter, who denied the accusations.

The mother testified that she told her daughter she intended to bring her to the doctor and call authorities. Only then did her daughter admit to having sexual intercourse, she said.

In cross examination by Joyce, the mother testified that not only had the blog revealed that there had been sexual contact between her daughter and Sanville, but the daughter had also sent pictures of herself when requested by an adult friend of Sanville. The mother did not indicate what type of pictures were sent.

Testimony revealed that Sanville had visited the family over the years, and on several occasions since his return from Iraq in July 2011. The mother said that when visiting, Sanville slept on a mattress on the living-room floor — at times with the 13-year-old daughter, her older sister and the sister’s boyfriend. Additionally, Sanville and the 13-year-old had been allowed on one occasion to sleep alone in a camper, which had a queen-size bed and a pull-out bed.

“I trusted him 100 percent with my daughter’s care and well-being,” the mother said.

The mother testified that on the night he is accused of assaulting her, she had allowed Sanville to drop her younger daughter off at home, where he came back to sleep after going to Bethel to drink with friends in a bar. She and her husband were away at their camp for the weekend.

“We didn’t discuss where Kyle would sleep that night because I trusted him,” she said.

The trial is scheduled to continue Wednesday.