Zurich, Switzerland ? A Russian architect whose family died when two planes collided was convicted and sentenced to eight years in prison Wednesday for the killing of an air traffic controller who was on duty at the time of the 2002 crash.

The Zurich Superior Court found Vitaly Kaloyev guilty of premeditated homicide in the stabbing death of air traffic controller Peter Nielsen. It was a lesser charge than murder and carries a maximum sentence of 20 years in prison under Swiss law.

Kaloyev, 49, acknowledged in court Tuesday that he must have killed the air traffic controller but said he could not remember doing it.

Kaloyev’s attorneys pleaded for manslaughter, saying the defendant was tormented by great psychological distress at the time of the crime and any prison term should not exceed three years. Defense attorneys had no immediate comment on the verdict.

Russia’s Justice Ministry told the Interfax news agency that it would try to have Kaloyev extradited so he can serve his sentence there.