The simple answer, experts say, is -- legally -- yes, Breivik could be considered sane. Insanity is a legal term, not a psychological one. So, even if Breivik has a mental disorder, he could still be sane in the eyes of the court if he had impulse control, acted with intent and was capable of understanding at the time of the attacks that what he did was wrong.
As with any legal standard, though, establishing sanity or insanity is a complicated and nuanced process.
"This has been an ongoing struggle for, literally, centuries," said Robert Schopp, professor of law and psychology at the University of Nebraska, Lincoln. "The idea is that some people are so severely impaired that they shouldn't be held responsible. But it's very hard to come up with a clearly defensible standard for insanity."
"The insanity defense is not a common defense," he added. "It's raised pretty rarely and it works even more rarely."
The theory behind punishment is that it should offer harsh consequences for wrongful acts. But if a wrongdoer didn't understand what he was doing -- because, say, he believed he was following orders from God or because hallucinations convinced him that a terrible act was necessary to save the world -- it is hard to justify condemnation. For hundreds of years, legal systems have struggled with how to handle cases like these.