FARGO (AP) - A teenager described by his lawyer as struggling with ''insurmountable demons'' after years of abuse apologized in court for killing his sister and asked for forgiveness.
Sergei Carlson, 16, was sentenced Thursday to life in prison for murder and a deviate sexual act in the July 2007 killing of Whitney Carlson, 16, of Fargo. The sentence includes the possibility of parole.
Carlson, wearing orange prison clothes and shackled at the waist and ankles, said softly he was ''very sorry'' for his actions.
Sergei Isaac Carlson, 16, reacts in a Cass County Courtroom as his defense attorney Mark Beauchene speaks Thursday in Fargo. Carlson was sentenced Thursday to life in prison for murder and a deviate sexual act in the July 2007 killing of his sister Whitney Carlson, 16, of Fargo.
''I didn't want any of this to happen,'' he told Judge John Irby before he was sentenced.
Authorities said Carlson strangled his sister in her bedroom and put a pillow over her face to muffle her sounds, then had sex with her. He originally was charged as a juvenile, but the case was moved to adult court because of his age and the severity of the charges.
''The severity of this crime - it really couldn't get any worse,'' Cass County prosecutor Tracy Peters said after Thursday's hearing.
Irby had rejected an earlier plea agreement that would have called for Carlson to serve 30 years in prison. He likely will be in his 60s before he's eligible for parole.
Defense attorney Mark Beauchene asked Irby to reconsider the 30-year sentence. Carlson has emotional and physical scars from an abusive childhood in his native Russia and might not understand his situation, the lawyer said.
''It's not that he doesn't want to. Perhaps he can't,'' Beauchene said.
Beauchene said his client has scars on his upper body where his mother cut him. Carlson eventually wound up in a Russian orphanage, where it appears he was physically and sexually abused, Beauchene said.
Sergei Carlson was adopted from Russia when he was 7. ''Unfortunately, that (Carlson) family was broken, as well, through divorce,'' Beauchene said.
Sergei Carlson had been living in Sun Prairie, Wis., with his father, the Rev. Scott Carlson. Whitney lived with her mother, Penny Ripplinger, and sisters in Fargo. Sergei Carlson was visiting the family when Whitney was killed.
''She (Whitney) was in her own room, in her own bed, when the defendant crept in and began his attack,'' prosecutor Reid Brady said during the hearing.
One of Sergei's sisters, Amanda Carlson, was the only person to speak during Thursday's hearing. She glanced at Sergei only once, and did not mention him by name.
''I'm his sister and I'll always love him, but he has forever lost my trust and he has forever lost my respect,'' Amanda Carlson said.
Both Amanda Carlson and Ripplinger recommended a sentence of life in prison with the chance for parole. Scott Carlson asked for a sentence of twice the length of Whitney's lifetime, or about 32 years.
Brady said an evaluation showed Sergei Carlson was considered high risk to commit another crime and showed no motivation to change his behavior. The teenager also admitted planning ''other acts of wrongdoing,'' Brady said. He did not elaborate.
Brady said factors in Sergei Carlson's favor included his age, the adverse affect of his childhood, his cooperation a few days into the investigation, and his guilty plea that spared the family from going through a trial.