CHARDON -- The sentence given to T.J. Lane for the Chardon High School shootings was the focus of an appeal hearing this morning at the Geauga County courthouse.

Lane is challenging whether he should have been tried in adult court. His attorney told an appellate panel that Lane's sentence of life without parole should be thrown out.

The prosecutor countered that Ohio law is clear that a 17-year-old who commits murder should be tried as an adult.

Lane was not in the courtroom for the brief hearing that lasted about 30 minutes.

The appellate panel took the issue under advisement. A ruling will be made later.

Watch the full hearing here:

Lane was 17 when he shot and killed three students and wounded three more in the Chardon High School cafeteria in February 2012.

Lane faced trial as an adult and pleaded guilty to charges. The judge sentenced him to three life sentences without the possibility of parole.

Lane is challenging a state law that requires a 16- or 17-year-old accused of the most severe offenses to be transferred to adult court if there is probable cause to believe he or she committed the act.

Lane's appeal said that violates the right to due process "because it prohibits the court from making any individualized determination of the appropriateness of the transfer of a particular child's case to adult court."

Prosecutors say Lane gave up his right to appeal his sentence when he voluntarily pleaded guilty. They cited U.S. Supreme Court precedent and a recent Ohio case.

"Under the eyes of Ohio law (Lane's) conduct was an adult criminal act," Geauga County Prosecutor James Flaiz wrote in response to the appeal.

As of 2012, there were about 2,500 people in the U.S. serving life sentences for homicides that occurred when they were juveniles, but the current number is difficult to track because a U.S. Supreme Court ruling that year raised the possibility that hundreds of those sentences may be called into question, said Marsha Levick, chief counsel for the Philadelphia-based nonprofit Juvenile Law Center.

Giving juveniles life terms without parole "means that we're making these decisions on Day 1 of sentencing about who Lane or any other juvenile will be 30, 40, 50 years from now," Levick said. "And it's almost impossible to make that decision or to know who he will become as an adult."