Breivik took a "sabbatical year" to prepare for attack On the fourth day of Anders Behring Breivik's trial, the Norwegian mass killer entered the Oslo district court without the clenched-fist salute he had used in previous hearings. Breivik has admitted killing 77 people in shootings and a bomb attack in Norway in 2011 and the key issue of the trial is to establish whether he is criminally insane. In his testimony, the 33-year-old said he played the computer game Modern Warfare for 16 months starting in January 2010 - primarily to get a feel for how to use rifle sights. Breivik said he decided in 2006 to carry out what he expected to be a "suicide" operation and took what he called a "sabbatical year" to prepare for the attacks. He admitted playing World of Warcraft, for 16 hours a day, cutting off social contact for a full year If found sane, Breivik could face a maximum 21-year prison sentence or an alternate custody arrangement that would keep him locked up as long as he is considered a menace to society. If he is declared insane, he would be committed to psychiatric care for as long as he's considered ill. The trial is expected to last ten weeks.