Complex sentence: Hamsun was forced to undergo a psychiatric examination, which concluded that he had "permanently impaired mental faculties", and on that basis the charges of treason were dropped.
Split into simpler sentences: Hamsun was forced to undergo a psychiatric examination, which concluded that Hamsun had "permanently impaired mental faculties". A psychiatrist concluded he had "permanently impaired mental abilities", and on that basis the charges of treason were dropped.