MARIETTA - The father of the teenage student involved in a sexual relationship with a teacher at Marietta High School told Cobb Superior Court on Tuesday, "I thought I had raised her better."

Testimony began - and was often interrupted - Tuesday afternoon in the criminal trial of Christopher King, 36, who is charged with one felony count of sexual assault against a person in custody. He was arrested May 27, and quit his job around that same time.

At issue is whether the sexual relationship between King and the student, 17, is illegal. State law allows consent to be used as a defense because the student is over 16, the age of consent in Georgia. The girl, whose name is being withheld by the Journal because she is alleged to be the victim of a sex crime, has testified at previous hearings that the sex was consensual.

Assistant District Attorney Maurice Brown is attempting to show that teenagers do not always make sound decisions, and that even though this student had sex with King voluntarily, she had been manipulated by an adult who was grooming her for a relationship to satisfy himself sexually.

"He led her to believe she was in love," Brown said in his opening, noting that the girl was 17, and King was a married father of two when their physical relationship began.

But Scott Semrau, King's defense lawyer, insisted in his opening statement to the jury of six men and six women that the relationship "was probably a bad idea, probably taboo. But not against the law."

Marietta High principal Leigh Colburn and Marietta Police Detective Paula Cowell were the first two witnesses called by the state.

Both Colburn and the student's father testified about a situation last fall that involved King and the student. A group of journalism students had taken a trip to the University of Georgia in Athens where a few of them, including this girl, were found drinking alcohol. King filed a disciplinary report against the girl and others when they returned to Marietta High, and she served a suspension.

Semrau pointed out that school authorities held the girl accountable for her actions in that incident, to which a visibly perplexed Colburn agreed they did. The girl's father said that during the one brief meeting he had with King last fall, he thanked King for disciplining his daughter in that incident.

Detective Cowell testified about her investigation into the King-student relationship and said the student told her that she did not feel she was being victimized. The two had sex at "a hotel on Barrett Parkway" and other times at his new residence, where he lived after separating from his wife. King now lives less than a mile from the high school where he had taught English and journalism since 2004.

The defense is also taking pains to point out that the student is a bright girl, has always maintained excellent grades, and had a job and her own car. She was a junior enrolled in the International Baccalaureate program at Marietta High at the time of the relationship. Although she is still enrolled there, she is completing her high school diploma through a joint-enrollment program at Kennesaw State University.

The trial will continue this morning before Judge Robert Flournoy III.