A jury in New London Superior Court on Monday convicted a 35-year-old father of a felony charge for forcibly dragging his 13-year-old daughter out of the West Side Middle School in Groton in September 2015 after she refused to leave with him for a counseling appointment.

Mark N. Thornton, of 8 Joseph Williams Road, Mashantucket, faces up to 10 years in prison when Judge Barbara Bailey Jongbloed sentences him Nov. 14 for risk of injury to a minor. He had been free on a $35,000 bond while his case was pending. The judge increased the bond to $50,000 after the verdict and ordered judicial marshals to take him into custody.

According to testimony at the trial, the victim, then an eighth-grader, suffered bruises and rug burns after Thornton dragged her by the wrists and ankles from outside of her classroom into the school's main office. Because of the victim's age, only her first name or initials were used during the trial.

The six-member jury, comprising three men and three women, deliberated for about four hours before finding Thornton guilty of risk of injury of a minor and not guilty of an additional charge of second-degree breach of peace.

In opting for a jury trial, he had turned down several plea offers from prosecutor Sarah E. Steere, including her final offer to not prosecute the case if Thornton attended counseling.

He had represented himself at his trial, with attorney Shawn G. Tiernan from the public defender's office serving as "standby counsel" if Thornton wanted legal advice.

School staff members who witnessed the incident had testified along with the daughter, who is now 14 and in the care of the state Department of Children and Families. School staff had issued a "code yellow" lockdown and called police and the DCF after the incident.

The daughter calmly told her story from the witness stand after the prosecutor reluctantly called her to testify as a state's witness. Had Steere not called the teen as a witness, Thornton had planned to issue a subpoena compelling her to testify for the defense.

"My dad dragged me across the floor from my classroom almost to outside the school," she said under questioning by Steere.

Attorney Denise Ansell, the teen's guardian ad litem, comforted the girl when she broke down, briefly, on the witness stand.

Thornton had also broken down on the stand when he called himself to testify about the incident. He said he had just gained custody of his daughter a month earlier and that she kept running away and would not listen to him.

"I was in desperate straits to get help for me and my daughter because every day the police were coming to my house," he said, wiping his face with tissues. "I didn't know what to do, but I didn't want her to go into the foster care system."

Thornton said he knows he should have handled it differently but thought he was justified in forcibly removing his daugther from the school. He said he had tried to quiet her and pull her into the main office when her screaming started drawing the attention of other students.

After the school secretary told him, "I think that's enough," Thornton said he let go of his daugther. She then curled up under a trophy case and cried, according to testimony.

At Thornton's request, the judge included an instruction to the jury about parental justification.

In her closing argument, the prosecutor said a reasonable person would have used the school staff to help Thornton de-escalate the situation.

"The defendant was the adult," Steere said. "He was the parent in this situation. He had school staff available to help him."

k.florin@theday.com