(CNN) -- Anders Behring Breivik promised Thursday that he would not appeal if a court finds him sane and guilty in charges tied to the killings of 77 people last year in Norway, his lawyer said.
"There is absolutely no reason to appeal if I am declared criminally accountable," Breivik said in court, according to his attorney, Ivar Gron.
Gron said the promise that there won't be an appeal is contingent on Norwegian judges first making a determination on his client's mental state.
Breivik is on trial on charges of voluntary homicide and committing acts of terror in the July 22, 2011, attacks. He has admitted carrying out an attack on a youth camp on Utoya Island that killed 69 people and a bombing in Oslo that killed eight.
He boasts of being an ultranationalist who killed his victims to fight multiculturalism in Norway.
Experts' assessment of Breivik's sanity will be a factor in determining what punishment he receives if convicted. Sentencing options could include imprisonment or confining him to a mental facility.
CNN's Laura Maestro Perez contributed to this report.